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©IPK30/04/17 COMPUTER GLOSSARY IPKversion30/04/17 03:47 -.bmp 24 bit true colour. Header up to byte 54 of the picture file. Byte 55 is the first pixel of the picture. Pixels ordered as Blue, Green, Red. Pixels start in the bottom LHS of the picture. -.EXE Files should have the two characters MZ right at the start which other programs accept as proof that a file whose name ends in .EXE is executable. -.NET "Software to connect information, people, systems and devices",(via the internet) Bill Gates. Three key pillars to .NET .NET framework - generation of applications for the internet age. The heart of this is CLR Common Language Runtime XML - Web services Smart clients - access for the internet. -1-pixel GIF Used by sites and advertisers to track precise browsing and movements without your knowledge. Not detected by cookie filters. Can also be used in e-mails. Look for IMG tags with the height and width parameters set to 1 -3D adaptor -3GPP 3D graphics adaptors work alongside existing video cards. Third Generation Partnership Project -3.4GHz Can support services up to 2Mbps over distances of about 10km -3.5GHz Offers 15Mbps at up to 27km -404 Not Found The computer found the web site server but the page could not be found. -10BASE2 A form of Ethernet and IEEE 802.3 network cabling using thin coax. The term refers to 10Mbps (speed) Baseband (transmission) 200m max. length, (in practice 185m). Up to 30 devices can be connected per segment length. The cable has a characteristic impedance of 50 ohms. Commonly called Thin Ethernet or Cheapernet. -10BASE5 A form of Ethernet and IEEE 802.3 network cabling using thick coax. The term refers to 10Mbps (speed) Baseband (transmission) 500m max. length. Commonly called Thick Ethernet. Ensure that all MAUs are at least 2.5m apart so that stations do not get lost due to standing waves. If joints are essential try to distance them at special magic multiples of 23.4m as this cuts standing wave effects. Also 50 ohm cable. -10BASE-T A form of Ethernet and IEEE 802.3 network cabling using twisted pair cabling. The term refers to 10Mbps (speed) Baseband (transmission). 10BASE-T recommends a segment length of 100m. Only two pairs actually used, connected to pins 1,2 and 3,6 avoiding use of the common telephone pair 4,5. Twisted pairs have an impedance of 100 ohms. ©IPK30/04/17 -10GE 10Gbps Ethernet. -100BASE-T A form of Ethernet and IEEE 802.3 network cabling using twisted pair cabling. The term refers to 100Mbps (speed) Baseband (transmission). 100BASE-T recommends a segment length of 100m. Expect transmission speeds of about 100MB in 1 minute on a 100Mbps network. -1000BaseT Gigabit Ethernet. Utilises all four pairs and transmitting 250Mbits per pair. -802.3ab Protocol for fibre optic gigabit connections. -802.3af Power over LAN. Provides power for devices as well as Data. -802.3z Protocol for copper gigabit connections. AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA -AAC Advanced Audio Coding. Used for on-line music stores. Based on Mpeg4 technology. Gives greater audio fidelity than MP3 but has digital rights management inbuild to prevent multiple distribution. -ACPI Advanced Configuration and Power Interface. Enables PCs to start quickly and have advanced power management facilities. Some reduce clock speed when full processing power is not required. -ACR Attenuation to Cross talk Ratio. -Acrobat To close down an Acrobat Document in a web browser, right click the Acrobat symbol on the task bar and select Close. -ACSA Anti-terrorism, Crime and Security Act, 2001 -ACT Alien Cross Talk is a feature of bundled cables. -Active Directory Replaces WINS and NT domains on win2000 and aims to give users access to permitted resources using a single logon process. Allows businesses to manage security, applications and privileges over the company network. The directory structure is created using the DNS mechanism. It is non-reversible. Active directory is managed through Microsoft's management console. Steps to planning AD. Create a forest plan Determine the number of forests Create a changevcontrol policy for each forest Create a domain plan for each forest Determine the number of domains Choose a forest root domain Assign a DNS name to each domain Plan DNS server deployment ©IPK30/04/17 Optimise authentication with shortcut trusts Create an organisational unit (OU) planh for each domain Create OUs to delegate administration Create OUs to hide objects Create OUs for group policy Create a site topology plan for each forest Define sites and site links Place servers into sites Active directory is based on Lightweight Directory Access Protocol (LDAP). Active directory is a directory service which stores information about network devices, resources and users. -ActiveX A set of interactive technologies developed by Microsoft, combining OLE (Object Linking and Embedding) and COM (Component Object Model). Unlike Java, ActiveX is not a programming language, but a set of instructions on how an object should be used. ActiveX controls can be downloaded from the Internet, and run just like Java applets. However, Java only interacts with the Web browser, while ActiveX controls can access the Windows operating system. -ADA A modern programming language designed for large, long-lived applications - and embedded systems in particular - where reliability and efficiency are essential. Based on Pascal and Algol, it was first developed by Honeywell-Bull to replace the many languages used by the US Department of Defence. It was named after Augusta Ada Lovelace, regarded by computer historians as the first programmer. The latest version is ADA2005. -Adapter The device that connects a piece of equipment to the network and controls the electrical protocol for communication with that network. Also called a Network Interface Card (NIC) -ADK Additional Decryption Key -Adobe Acrobat Built on PostScript, a page description language. -ADR Advanced Digital Recording. Philips format for back up tapes. -ADSI Active Directory Service Interfaces. A set of interfaces that enables developers to query and manipulate directory service objects. -ADSL Asymmetric Digital Subscriber Line. You have to be within 5.5km of an ADSL exchange to get a 512kbps service. If closer than 3.5km can get 2Mbps. It is the total line length and not the distance to the exchange that matters. The line to the exchange must also be of good signal quality. Dial 17070 and select options 3, 1 and 2, then BTs system will check the length of the line and call you back with the results. See DSL. -AES -AFC Advanced Encryption Standard Antiferromagnetically Coupled. When Ruthenium is layered three atoms thick between the two magnetic layers of the disk platter it stabilises the storage medium which would otherwise be prone to errors arising from small temperature changes. This occurs ©IPK30/04/17 when the density reaches 20-40Gbits per square inch. Significantly increases the storage capacity of hard disks. -AGP Advanced/Accelerated Graphics Port. Designed for 3D graphics cards, the AGP slot will award special priority to the graphics card so that it doesn't have to compete with everything else in the system, thus maximising the PCs video processing speed. AGP graphics cards can access system memory directly as well as their own memory. AGP 2X has a peak transfer rate of 512MBps while the AGP 4X runs at 1.1GBps. -AI Artificial Intelligence. See Brain -AirPort AppleMac Wireless Network System. -AIT Advanced Intelligent Tape. Sony's back-up tape format. A helical scan system. AIT-2 cassettes have a capacity of 50GB and a transfer rate of 6MB/s. AIT-3 expected to have capacity of 100GB per cassette and a transfer speed of 12MB/s. AIT's Memory is Cassette (MIC) is a small flash ROM chip mounted in the cassette that allows access to indexing and system log information without accessing the tape -AJAX Asynchronous Javascript plus XML. A collection of technologies and techniques intended to make web applications as responsive, interactive and rich as their desktop equivalents. Instead of reloading the page each time a user makes a small change, Ajax enables small amounts of data to be exchanged with the server asynchronously. Originally developed by Jesse James Garrett in his article in 2005 entitled Ajax: A New Approach to Web Applications. The current most high profile user is Google. -Aliasing The unwanted jagged appearance that may affect diagonals in images displayed on the computer. Removal of the notchy effect is called anti-aliasing. Occurs when there aren't enough pixels to represent a smooth line. There are several ways of antialiasing, from calculation intensive edge-anti-aliasing to the more common FSAA (Full Scene AntiAliasing) first implemented by 3dfx. Modern graphics cards generally fall into two categories Supersampling and Multisampling. Both are algorithmic approaches requiring some GPU calculations. Supersampling anti-aliasing - used by Nvidia's GeForce2 series and Radeon 7000 series of graphics cards. The picture is internally rendered at a higher resolution ie 4x, so that an 800 x 600 scene is rendered internally at 1600 x 1200 pixels, with each pixel of the original scene subdivided into four subpixel samples. Each of the four sub pixel samples contains separate colour data, so the final pixel colour is determined by blending the samples. This blurs transition boundaries which appear less jagged. Very demanding on hardware especially at high resolution. SmoothVision is a version of SuperSampling, where randomised samples are taken rather than from an ordered grid. Multisampling supported by Microsoft in DirectX 8. It increases the resolution by storing copies of the screen which are slightly shifted in the x and y axes. Multisampling concentrates on subpixel edge coverage ie by averaging the intensity. This can lead to some loss of quality compared to Supersampling, but the bandwidth requirements and hardware demands are less. -ALDC -ALGOL Adaptive Lossless Data Compression Algorithmic language - developed in 1958. The first to use formal grammar and block structure. Not used today. Pascal is probably the closest derivative and is the ©IPK30/04/17 language behind Delphi. C was also developed from Algol in 1972 but is more cryptic than Pascal. See C++ -ALT * Enter Enter ESC Print Screen Spacebar Spacebar + c Spacebar + m Spacebar + n Spacebar + s Spacebar + x TAB Switches between a window and a full screen. to view the properties of a selected item Cycles through the apps in the order they were started. Copies an image of the active window to the clipboard. Displays the program's System menu Closes the active window Moves the active window with the arrow keys Minimises the active window Resizes the active window with the arrow keys Maximise the active window Switches between programs. -ALT Gr key In combination with a vowel gives that letter with an acute accent. It also does the same job as pressing CTRL + ALT. -AML Active Messaging Library -AMR Audio Modem Riser. Now usually replaced by CNR -ANSI American National Standards Institute -AP Wireless Access Point - supports up to 35 concurrent users over 100m radius -Apache Web server for UNIX. Also a version for Windows. -API Application Program Interface. A common interface that allows programs to make use of services provided by the operating system or other applications. Winsock, is an API that allows Windows and other programs to talk to TCP/IP for internet access. They provide a library of ready made functions and tools that programmers can use. For graphics processors examples are OpenGL and Microsoft's DirectX -Aperture Grille Use a horizontal grid of fine metal wires that run up and down the screen to direct the beam. This grid creates slots that have the same effect as the holes found in a shadow mask. To hold the grid in place, two fine wires run vertically across the top and bottom of the screen which can sometimes be seen. Image sharper and brighter than shadow masks and tube face is flatter. -APM -APN Orange orangeinternet -APNIC Application Performance Management Access Point Name of a GPRS network. For O2 Vodafone internet Asia Pacific network Information Centre mobile.o2.co.uk ©IPK30/04/17 -APPC Advanced Peer to Peer Communication. A network architecture definition by IBM. -Applet A program designed to be executed from within another program. Cannot be activated from an operating system. Written in Java. Adhere to a set of conventions that lets them run within a Java-compatible browser. -Appletalk Used to configure Apple Mac computers into small workgroups. Uses specialised cables and network interface cards to transmit data at speeds around 230Kbps. -Application Layer The highest layer of the seven layer OSI model structure with all user or application programs. -Application server Runs an application for a client. -APU Audio Processing Unit -Archie an FTP search engine invented in 1992. -ARP Address Resolution Protocol. Consider two machines, A and B sitting on the same IP network. When machine A starts to transmit IP traffic to machine B it examines the destination IP address. As machine A knows that machine B is on the same network, it has to find out B's Ethernet address. It sends out a broadcast ARP request to all machines on the Ethernet network, essentially asking "who has B's IP address?". All machines on the network get the request and check their IP address. When B finds that it is being contacted, it sends a response back to machine A. A now builds an Ethernet frame and puts the IP packet in the payload field. The frame is then sent over the Ethernet network to machine B. When B decodes the frame, the IP packet is passed up to the IP software and dealt with in the usual way. There are several ways to improve the efficiency of this process. All machines maintain an ARP cache. Everytime a machine wants to send a packet it checks the cache to see if it has the correct mapping. If it does then it does not send out an ARP request. Because IP addresses can be assigned to different machines, the ARP cache has to time out at regular intervals. ARPs can also be setup so that each machine broadcasts its IP/Ethernet address mapping on boot. This causes each receiving machine to add the mapping into their local ARP caches. ARP runs into trouble when routers are involved. Routers will not pass on Ethernet broadcasts which makes it difficult for devices on different subnets to communicate. The workaround is to have the router respond to all ARP requests for foreign networks. From this point on all machines will quite happily send further packets to the router. This means that routers, and switches have to be able to store thousands of address mappings locally. In a switch this is used to help the switch pass the correct frames out of the correct port. See RARP Reverse Address Resolution Protocol. -ARPANET The forerunner of the Internet. ARPA is the Advanced Research Project Agency, the US department of Defence Agency that funded the development of the first computers to link networks across great distances. -ARQ Automatic Request for Retransmission -ASA Advertising Standards Agency. ©IPK30/04/17 -ASCII American Standard Code for Information Interchange. Most often encountered as the ASCII character set, a group of 96 lower and uppercase characters plus 36 nonprintable control characters. -ASIPs Application Specific Instruction Processors -ASP Application Service Provider. -ASP Active Server Pages. Supported by windows 2000 and Microsoft Internet Information Server. Based on VB Script and initially released in 1996. ASP instructions have to be placed with <% and %> tags. The code works by calling a standard object such as a response or request followed by a method you wish to invoke separated by a dot, as well as any further parameters in brackets. eg <% Response.Write("Hello world!")%> -ASP.net Pages are compiled, overcoming the poor performance limitation of 'classic' ASP. An ASP application is essentially a set of pages containing controls. Most code is done on the server rather than on the user's machine, and the HTML produced will work with any browser. -Assembler Translates from a low level language to machine code. It produces an object code file. -Asynchronous Transmission Transmission in which time intervals between transmitted characters may be of unequal length. Transmission is controlled by start and stop bits at the beginning and end of each character -ATA AT Attachment. First introduced in 1986. ATA-4 introduced in 1997 - also known as UDMA or ATA33. Data transferred at 33MB/s ATA-5 introduced in 1998 - also known as ATA66 - runs at 66MB/s. This has an 80 wire cable. The cable is colour coded. The blue plug goes to the motherboard, the black is the master and the grey is the slave. Despite the rating, the maximum speed for any parallel HDD is around 45MB/s in practice -ATAPI Advanced Technology Attachment Packet Interface. A standard for connecting a CD-ROM drive to an Enhanced IDE adapter. -Athlon processors Use Socket A which contains 462 pins -ATM Asynchronous Transfer Mode. A high speed networking technology that transmits various kinds of information by creating packets of data. Can be extended to an almost indefinite distance. Uses fibre optic cabling to deliver data at 155Mbps. A method for the dynamic allocation of bandwidth using a fixed sized packet (called a cell). Uses 53-byte cells. This was used over fibre by carriers in the 1990s, but was never popular with end users since it required the displacement of existing Ethernet networks. Subsumed by standard IP packets. -ATM Automated Teller Machine ©IPK30/04/17 -ATS Access through Share. Share permissions in WinNT. Independent of any local NTFS or directory level permissions. More limited than NTFS directory shares. -ATX Advanced Technology Extended. -Attenuation The decrease in the strength of a signal over the length of a cabling channel and is caused by a loss in electrical energy in the resistance of the cabling channel and by leakage of energy from the channel -AUI Attachment Unit Interface. Normally a 15way D type connector as the interface between the Ethernet transceiver and the network device. -AUP -AUTOEXEC.BAT Acceptable User Policy It is a series of instructions:- tells the PC which software drivers to load, how much memory to use as buffers, etc It is the second file to be loaded when the PC is turned on. C:\WINDOWS\COMMAND\SHARE.EXE /L:500 /F:5100 Prevents the same document being opened more than once at the same time. Uses about 10K of base memory. LH /L:1,32096 C:\SBCD\DRV\MSCDEX.EXE /D:MSCD001 /M:8 /V Makes the CD-ROM drive work. The /M:xx switch tells DOS to use a section of memory as a buffer for information coming from the CD-ROM drive. the higher the figure, the more the buffer is, and that means the faster the CD seems. A good figure is 10 to 100. SET BLASTER=A220 I5 D1 H5 P330 T6 Sets the rules for the sound card for when other software is looking for it. ECHO OFF Stops autoexec.bat file being echoed on the screen. PROMPT $P$G Tells the PC to display the full path in the prompt, ie C:\DOS> LH /L:1,29472 C:\MOUSE\MOUSE.COM Loads the mouse driver especially for DOS. SET MOUSE=C:\MOUSE Sets the mouse type???? PATH C:\WINDOWS;C:\DOS; A listing of directories in which DOS looks whenever a command is typed. It first looks in the WINDOW directory then the DOS directory. SET TEMP=C:\WINDOWS\TEMP Sets the TEMP directory for programs that need to store temporary files. LH /L:0;1,45456 /S C:\WINDOWS\SMARTDRV.EXE /X 2048 128 Smart drive loads commonly used information into the machine memory, where it can be accessed faster. MODE CON CODEPAGE PREPARE=((437) C:\DOS\EGA.CPI) Refers to the way in which DOS characters are displayed on the screen. MODE CON PAGE SELECT=437 Same operations as above. LH /L:1,16656 KEYB UK,,C:\DOS\KEYBOARD.SYS Converts characters on the screen to English. ©IPK30/04/17 -Autorun Create a text file named autorun.inf in the CDs root directory. The first line of the file should contain only the text [autorun] To run a program type open= eg to run explorer automatically the file should read [autorun] open=explorer.exe /n,/e,. (yes comma and full stop!) The n means open in a new window and the e tells explorer to open in expanded view. A full list of commands for autorun can be found at http://msdn.microsoft.com/library/psdk/shellcc/shell/shell_basics/autoplay_cmds.htm Avalon The Windows presentation subsystem in Windows Vista. -Average Seek Time The average time it takes the drives head to find the data on the drive's surface. -AV Ready A drive that is able to transfer a minimum of 3MB/s, which is the amount required for broadcast quality video. -AVI Audio Video Interleave. Movie standard. Windows native format. High quality video and sound but large files. Not supported by Macs. Designed by Microsoft to combine audio and video in a single track or frame to keep them synchronised. BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB -Backbone The part of the network that carries the heaviest traffic. Used to connect different sections of LANs together. -Backup Facility in Windows. Located in Start, Programs, Accessories, System Tools. GRANDFATHER, FATHER, SON ROTATION SCHEME Son 1 Monday Every Monday Weekly Son 2 Tuesday Every Tuesday Weekly Son 3 Wednesday Every Wednesday Weekly Son 4 Thursday Every Thursday Weekly Father Week 1 Father Week 2 Father Week 3 Father Week 4 Father Week 5 (if needed) Grandfather Month 1 First Friday Second Friday Third Friday Fourth Friday Fifth Friday Last Business day Month 1 Monthly Monthly Monthly Monthly Monthly Quarterly Grandfather Month 2 Grandfather Month 3 Last Business day Month 2 Last Business day Month 3 Quarterly Quarterly Set A Set B Set C TOWER OF HANOI ROTATION SCHEME Every Other Day Two Days Every Fourth Day Four Days Every Eighth Day Eight Days ©IPK30/04/17 Set D Set E Every Sixteenth Day Alternate with Set A Sixteen days Thirty two Days -Back plane PC & AT ISA (AT) EISA VL PCI PCI-X -Balun 8 bit 16 bit 32 bit 32 bit 32/64 bit 64 bit 6MHz 8 - 10 MHz 8MHz 33MHz 33/66MHz 133MHz Connects balanced to unbalanced cables. -Bandwidth The maximum amount of data that a network cable can carry. -Banias Microcode architecture used by Intel on its mobile processor chips. -Barcodes First patented in 1949. RCA demonstrated the first barcode (a bulls eye) in 1971. IBM developed the UPC (Universal Product Code) barcode system which became the industry standard in 1973. In Europe we use a variation of the EAN (European Article Number) of the UPC. The UPC/EAN code used on retail products is an all numeric code. Code 39 includes upper case letters, digits and a few symbols. Code 128 includes all ASCII characters. A barcode always conforms to a fixed format. Eg around an EAN-13 barcode are four corner marks that form a rectangle. These define the printable area for the code. Inside these are the so called quiet zones, a clear border devoid of marks. On the left, middle and right of the code are special bars called guard bars. The left and right guard bars indicate the beginning and end of the code, while the centre guard bars separate the code into two zones. The actual number that the code represents is printed at the bottom. This too has a fixed format - the first two characters are the flag characters, which identify the country of origin. The next ten characters are called the data characters, the first five of which identify the manufacturer and the last five identify the product. The last character is the check-digit for the check sum. The practical limit for a standard barcode is 20 to 25 characters. -Baseband A transmission technique employed in LANs. Only one device can communicate at one time and a device simply sends its digital signal on to the cable without any modification. -Basic Computer language. Written by John George Kennedy and Tom Kurtz in 1964. Qbasic is on the W95 CD in the folder \ other\Oldmsdos. Uses an interpreter instead of a compiler to translateprogram statements to machine code and execute them one line at a time. Developed into Visual Basic in 1991 by Microsoft to simplify development of windows programs. -Batch files To make close automatically, right click the batch file in Explorer and choose Properties. Click the program tab. Check the box for Close on exit. For a program to run undisturbed until it finishes and closes add the command start/w to the beginning of the line. To make a pause use the line choice/n/t:y,xx where xx is the pause in seconds. ©IPK30/04/17 Batch files expect windows programs to multitask so they won't wait for one to close before the next starts. To make a program finish before the next one starts add the command start/w. To close a batch file window when it has finished end it with the command CLS. This command must be the only item on the last line - it should not have a return after it. Can be created in any version of DOS above 5.0. With W95 a windows program can run from within a batch file. Programs can run sequentially or simultaneously. By default, batch files expect Windows programs to multitask. To make a program finish before the next begins add the command start/w at the beginning. A batch file is a script file containing anything that you might type at the DOS prompt, and each command must be on its own line. Create a batch file in Notepad or Edit. Save with the extension .bat. To edit a batch file, right click the file's name in Explorer and select Edit. This summons the file in Notepad. ping 192.168.254.254 > ping.txt find "TTL" ping.txt goto ping%ERRORLEVEL% :ping1 xxxxxx :ping0 xxxxxx If TTL found then ERRORLEVEL = 1. If TTL not found then ERRORLEVEL = 0 XCOPY the switch /D ensures that if the file already exists on the target disk then it is not recopied unless its date is more recent. /S forces XCOPY to look in sub directories. If using long file names, enclose the whole path in quotes " " ECHO OFF stops subsequent commands being displayed on the screen. Typing @ECHO OFF stops the ECHO command itself appearing. Starting multiple programs from one batch file:eg start C:\windows\notepad.exe start C:\windows\calc.exe -Baud Unit of signalling speed. The speed in baud is the number of line changes or events per second. Usually greater than the bit rate. -Bell 212 An AT&T specification of full duplex asynchronous or synchronous 1200 bps data transmission for use on the public telephone network. -BEN Backbone Edge Node - key connection points on the JANET backbone. The BENs are managed by UKERNA as JCPs. -BERT/BLERT Bit Error Rate Testing/ Block Error Rate Testing. An error checking technique that compares a received data pattern with a known transmitted data pattern to determine transmission line quality -BGA Ball Grid Array -BGP Border Gate Protocol -BGP4 Border Gateway Protocol 4 - a path vector protocol and works on the principal of routing tables. ©IPK30/04/17 -BHO Browser Help Objects. .dlls that allow developers to customise and control Internet Explorer. A list of malware BHOs is available at Computercops.biz -BIND Berkeley Internet Name Domain. The dominant DNS software used on the Internet -BIOS Basic Input Output System. Software, usually held in ROM which tells the operating system what hardware components the PC has. Also provides keyboard and video control when PC is first switched on and provides checks on resources. Back door passwords: Award BIOS (upper and lower case) award sw, award_sw, award pw, _award, award?sw, biostar AMI BIOS (upper and lower case) ami, a.m.i., aaammmiii, ami sw, ami_sw, bios, password, biostar, biosstar. Phoenix BIOS phoenix, cmos, bios Also try clearing the password. Boot to MS-DOS, type Debug then for an AMI or Award Bios enter 0 70 17 0 71 17 Q For a Phoenix Bios enter he following code, using he capital letter O not zero O 7O FF O 71 17 Q -BIST Built In Self Test. -Bit Binary digIT. Invented by Claude Shannon. -Biztalk Industry initiative to integrate business applications and processes - adopted by Microsoft -Blade Technology that eliminates the need to buy separate power supplies, fans and management cards for every different server you decide to put in a rack. Instead you just pop blades with different network technologies into one chassis which shares power, cooling, cabling and infrastructure management. Often designed to occupy one rack unit in height 1U or 1.75". -Bluetooth Designed to provide a common standard for wireless communication between all computing devices from PCs and printers to PDAs. Uses frequency hopping technology to provide a bandwidth of 1Mbps over a distance of 100 metres. Developed by a special interest group led by Intel, Ericsson, IBM, Nokia and Toshiba. Designed to operate in a noisy radio frequency environment. Operates in the unlicensed ISM band at 2.4GHz with a gross data rate of 1Mbit/s on a shaped, binary FM modulation. Designed for an aerial power of 0dBm, but spectrumspreading has been added to allow optional power levels up to 100mW by frequency hopping in 79 hops displaced by 1MHz, between 2.402 and 2.480GHz. This bandwidth is reduced in some countries. The maximum frequency hopping rate is 1600hops/s and the nominal link range is 10cm to 10m. The baseband protocol is a combination of circuit and packet switching, where slots can be reserved for synchronous packets and each packet is transmitted in a different hop frequency. Bluetooth can support an asynchronous data channel, up to three simultaneous synchronous voice channels or a channel which simultaneously supports asynchronous data and synchronous voice. each channel supports a 64Kbit.s synchronous voice link while the asynchronous channel can support an asynchronous link up to 721Kbits/s in either direction, while permitting 57.6Kbits/s in the return direction or a 432.6Kbit/s symmetric link. The voice channels use continuous variable ©IPK30/04/17 slope delta modulation (CVSD) voice coding scheme and never retransmit voice packets. Chosen because even at a bit error rate of 4%, the CVSD coded voice is quite audible. Bluetooth. Named after the 10th century Viking, King Harald Bluetooth who lived in Denmark between 910 and 940AD. Because of Bluetooth's communication skills, Denmark and Norway became Christian countries and united during his rule. Bluetooth or Blatand in the old Viking language, means dark complexion - he had very dark hair. The first concept of the technology that became Bluetooth was created in Lund in Sweden in 1994. Bluetooth 2 likely to increase bandwidth to 2Mb/s Bonding Bandwidth on Demand - the technique of inverse multiplexing to link the two B channels of a ISDN line to form one high speed circuit capable of running at 128Kbps. Boot Disk Windows 3.1 Format a:/s Needs IO.SYS, MSDOS.SYS, COMMAND.COM, AUTOEXEC.BAT, CONFIG.SYS, FORMAT.COM, FDISK.EXE AND EDIT.EXE Also useful to have AUTOEXEC.BAT, CONFIG.SYS, WIN.INI and SYS.INI. Windows 95 Left click Start, Settings, Control Panel, Add-Remove programs, Startup Disk Tab. Insert disk then left click CREATE button. To check disk, turn off computer. Insert disk into A: drive and turn on system. Hard print copies of AUTOEXEC.BAT, CONFIG.SYS, WIN.INI and SYS.INI. In Windows 95 the crucial files are SYSTEM.DAT and USER.DAT. To create a boot diskette, insert a diskette into the A: drive. At the DOS prompt type SYS A: and press enter. Also copy over FDISK and FORMAT. PREPARING A HARD DISK FOR DATA. Use Bootable diskette to start system. Run FDISK.EXE from boot diskette. Choose Create DOS Partition or Logical DOS drive. Select Create Primary DOS partition. etc. Then format hard drive by typing FORMAT C:/S, which will transfer the necessary system files and make it bootable. ABSOLUTE MINIMUM BOOT DISK (win95) Format a floppy as a system disk (format a:/s. Create a config.sys file containing: device=c:\windows\himem.sys device=c:\windows\emm386.exe noems novcpi dos=high,umb If running Win3.1 and Dos6, then substitute your DOS directory for c:\windows. Create an autoexec.bat file containing prompt $p$g path c:\windows;c:\windows\command loadhigh keyb uk Again substitute DOS directory for c:\windows\command if using DOS 6.22 Copy CD-ROM and sound card drivers from existing config.sys and autoexec.bat files. Replace device statements in config.sys with devicehigh and in autoexec.bat replace load with loadhigh. Copy the Set Blaster line in autoexec.bat. Set is a DOS command, not a program, so it does not need loadhigh. CREATING A BOOT DISK.(win95) 1). Insert a floppy disk. Open My Computer, right-click the A icon and select Format. Click the Copy System files check box, then click start. When complete click Close twice. ©IPK30/04/17 2). In Notepad, open file Windows\Dosstart.bat, then save it as a:autoexec.bat. Look for a line in the file containing 'mscdex.exe', then delete everything up to it - the first word in the line should be 'mscdex.exe'. Remove all subsequent lines as well. 3). Copy the file Windows\Command\Mscdex.exe on to the boot floppy in the A drive. 4). Back in Notepad, open config.sys on the C drive and look for a device=command that might be your CD-Rom drive. Save it as a:config.sys. Remove any path so that the line reads device = file 5). The device=line refers to a file by its path and name - c:\nec_ide.sys for example. Copy that file to drive A. Then remove the path from the line in a:config.sys. For example, if the line reads 'device=c:\nec_ide.sys/d:neccd0', trim it to device=nec_ide.sys/d:neccd0. -Boot sector Virus Infects the section of a floppy or hard disk that contains operating system and file information. Each time an infected PC starts the virus can spread. -Bowman The Army's digitisation program Towards the end of the 19th century, a Spanish scientist, Ramón y Cajal revealed for the first time the structure of the brain. He found a mass of cells (neurons) with long extensions (axons) that connected to numerous other neurons – some close by and others far away. By the middle of the 20th century, the model of a trunk telephone exchange, with neurons acting as switches was well established. When the electrical activity of individual neurons was examined, it was found that they did seem to be working like switches, with each cell producing a suitable electrical output when stimulated by a suitable number and combination of input connections. Many modelling attempts were made using Boolean algebra. At around the time of the start of the second World War there were two crucial publications: A Logical Calculus of Ideas Immanent in Nervous Activity by two neurologists Warren McCulloch and Walter Pitts, and A Symbolic Analysis of Relay and Switching Circuits by the communications engineer Claude Shannon. These two papers established the whole field of digital logic and meant that systems (including the brain) could be analysed in terms of the basic logic functions of AND, OR and NOT. Unfortunately, there was one serious flaw in the work of McCulloch and Pitts – they had assumed that the neuron was just a simple binary switch. In fact neurons behave more like nonlinear analogue devices or multistate, rather than binary, digital ones. It was not until the late 1960s that the problems were fully recognised. The subject of Cybernetics, or control systems developed at this time as a result of the joint work by computer and neuro-scientists. In 1952 a book called Design for a Brain, was published by a British psychologist, W. Ross Ashby. In this he applied the principles of logic in order to try to understand how the brain can produce adaptive behaviour – i.e. how it can learn to modify its actions in the light of experience, rather than just operate in a strictly rigid way. There were also attempts by computer scientists to build intelligent machines using basic electronic neurons called perceptrons. It all ended in the late 1960s when AI expert Marvin Minsky published a criticism of the futile attempts to build such machines and neurologists realised that neurons were much more complex that they had thought. Comparison of a brain with a computer. The brain is not a synchronous device and does not need regular clock pulses to keep its operations in step unlike a modern computer. Trying to establish an effective clock speed for the brain by doing a simple calculation would show that the brain runs at a clock speed of less than 100Hz! To compensate for this a brain is organised for massively parallel computation rather than having to push everything through a single CPU. There are around 1011 in a human brain and each of these is estimated to have an average of 103 connections to other neurons, giving a potential 1014 connections or synapses. However, it is -Brain ©IPK30/04/17 unknown how many are needed to perform any particular task or how many are available for that task. The brain consists of many specialised areas, for vision, motor control, smell etc so the number of synapses that can be recruited for a particular task will be just a tiny proportion of the total. However, this is considerably better than any form of parallel processing that exists in electronic form. Memory comparisons are also difficult to make. In the brain, memories are believed to reside in the strength of synaptic connections and so there are around 1014 memory locations. In his book, The Age of Spiritual Machines, Ray Kurzweil estimates that it would need about 10 bits to define each synaptic connection, giving an equivalent total memory capacity of 1015 bits. This is unlikely to be accurate since it can not be assumed that every neuronal connection is available for memory. It is also likely that each synapse may be part of many different memory patterns, so the efficiency of those synapses that are used for memory storage may be high. However, as an estimate, 1GB of memory contains around 1010 bits. So 100,000 PCs, with 1GB of RAM, would have the potential same storage capacity as a brain, or in terms of 100GB hard disk drives, only 1000 would be needed for the same potential storage. The brain is constructed as a vast neural network in which thoughts and memories are spread out across the network rather than relying on the conventional von Neumann computer architecture of a single processor and addressable memory. Techniques for studying the brain have improved from the stage of examining the brains of dead stroke victims to using brain scanning techniques. Two scanning techniques are available: PET – Positron Emission Tomography and fMRI – functional Magnetic Resonance Imaging. Both rely on the fact that more oxygenated blood flows to active neurons than to those that are not working. PET needs the patient to be injected with water containing positron-emitting Oxygen 15. Where there is more blood flow there will be more positrons emitted. PET gives a resolution of around 7mm and needs a sample time of around 30 seconds. fMRI relies on the slight difference in the magnetic properties of oxygenated and de-oxygenated blood and has a resolution of around 2mm and needs a sample time of 10 seconds. The patient needs to be absolutely still with each scanning method. -BRI Basic Rate Interface - ISDN line configuration giving two 64Kbps data channels and one 16Kbps overhead channel. Combines voice and data over a single service line. -Bridge Used to connect two or more LANs to form a larger LAN. Can improve performance and security. Bridges function at the data link layer of the OSI model. -Broadband Multi-channel analogue transmission technique employed in LANs. The signals on the network are divided, usually by frequency division multiplexing, to allow more than one signal on the cable at any one time. Requires MODEMs for all devices wishing to access the network. ADSL =>2Mb/s down ADSL2 =>8Mb/s down ADSL2+ =>24Mb/s down HSDPA =>1.8Mb/s down WiMax =>4Mb/s down VDSL =>4Mb/s down SDSL =>2Mb/s down WiFi =>2Mb/s down 3G =>384kb/s down ©IPK30/04/17 -Browser A client software program used to search networks and retrieve and display copies of files in an easy to read format. They can also call upon associated programs to play audio and video files. Microsoft Internet Explorer and Netscape Navigator are the most commonly used. -BS7799 British standard for data security -BSC Bisynchronous Transmission. A byte or character orientated IBM communications protocol. It uses a defined set of control characters for synchronised transmission of binary coded data between stations. -BTX Balanced Technology Extended. -Buffer An amount of memory that is used to store frequently used data. -Buffer Overflow A situation in which the buffer (a software stack used for holding data while it waits to be transferred) becomes flooded with code that then leaks into a system's main memory. This can result in code being executed. -Bugbear Virus. Can disarm antivirus and firewall software. Has key logging facility. Appears as an e-mail. Mails itself to recipients in e-mail address books. -Bump mapping This lets software make indentations in the scenery to add realism. Waves can easily be added to water etc -bus The internal pathway for signals moving around inside a computer, transferring data between various components. -Bus In LAN technology, a linear network topology; contrast with ring or star. All of the computers are connected to a single wire (or bus) which forms the central highway for all network traffic. -Bus master An intelligent device such as a PCI adapter card that can gain control of the bus and use it to transfer data without involving the processor. -Byte Eight bits or binary digits. 1KB = 1024 bytes. 1MB = 1048576 bytes. CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC -C# Microsoft Programming Language -C++ First published in 1983. A derivative of Algol. Overcame some of the short comings of C. Supported Object Oriented programming, a technique that allows complex code to be encapsulated in simple to use building blocks called Objects. -Cache A chunk of high speed memory used for speeding up operations in a PC. External (L2) cache is on the motherboard and is often 512KB. AMDs latest chips have 2MB. ©IPK30/04/17 The fastest cache memory is Level 1 and is used for the most frequently used information. Usually stored directly on a special section of the processor chip. Pentium IIIs have 32KB of L1 cache on the processor chip and either 256KB of L2 on-chip or 512 of L2 off chip. For high end processors it can take from one to three clock cycles to fetch data from L1, while the CPU waits and does nothing. It takes six to 12 cycles to get data from a L2 on the processor chip and dozens or hundreds of cycles for off chip L2. Intel planning in 2001 to introduce level 3 cache in its 64-bit server processor called Itanium. The 2MB or 4MB cache will connect to the processor via a bus that runs as fast as the processor i.e. 800MHz. -Camera/shy Allows users to hide and view sensitive data inside picture files to prevent detection -CAM Content Addressable Memory -CAN Control Area Network -CAPI Computer Application program Interface -Cardbus Enables PC cards (PCMCIA) to be hot swapped on notebooks. -CAS Column Address Strobe. A signal which tells the DRAM to accept a given address as a column address -Category 3 Voice and data transmission up to 16MHz or 10Mbps. -Category 4 Voice and data transmission up to 20MHz or 16Mbps. -Category 5 Cabling to 100MHz. Must meet standards of the design definitions of ISO 11801 and TIA 568-A. Must also meet the test definitions of TIA TSB67. -Category 5E Cabling to 100MHz, but must be able to pass greater tests. Provides an improved Attenuation to Crosstalk Ratio (ACR) and return losses compared to conventional CAT5. -Category 6 Cabling to 200MHz. -Category 7 Cabling to 600MHz. -CAV Constant Angular Velocity. Used with CD ROM drives. Data on the outside of the risk read faster than that on the inside. -CAM Content Addressable memory. Designed to accelerate any application that requires fast searches of list based data. Different to normal memory where data is stored in specific locations called addresses. When there is a need to retrieve the data, an address is supplied to the memory, which in turn returns the data. In CAM the opposite occurs. Data is supplied to the memory via a special comparand register and the memory returns an address if a match is found, enabling extremely quick searches to be made. The entire CAM is searched in a single clock cycle ©IPK30/04/17 -CCD Charge Coupled Device. Used in digital cameras to capture images. Each pixel of the sensor stores an electric charge proportional to the amount of light that strikes it. The brighter the light the higher the charge. At the end of the exposure, the charge is digitised and assigned a brightness value. The pixels in most sensors only record brightness and are unable to see colour. To make a colour picture, each pixel is normally covered by either a red, green or blue filter. Groups of four pixels are arranged in a two-by-two 'Bayer' pattern featuring one red, one blue and two green filters, since the green wavelengths contain the most image detail. The camera software then interpolates the filter data to create a full coloured image. -CCIR Centre for Communication Interface Research -CD-DA CD-Digital Audio -CD DRIVES Single speed data transfer 150Kbps. Spiral of tiny pits pressed into a plastic substrate starting from the middle and working outwards. A typical audio CD about 5 billion possible pits. The plastic substrate is coated with a very thin layer of aluminium. On a CD the pits are a minimum of 0.83microns long. DVD pits are 0.4microns and 0.74 microns apart rather than 1.6microns on current CDs. DVDs currently hold 4.7Gb. The substrate of a gold disk is similar to that of a silver disk. This substrate is covered first with a thin layer of cyanine dye and a thin layer of gold is sputtered onto this layer of dye. When writing to the disk a higher power red laser is used. When the equivalent of a pit is required, the write laser is switched on and the energy in the fine beam is absorbed by a dot of cyanine dye which explodes and creates a minute distortion of the gold layer. Gold disks have a better signal to noise ratio than silver disks. The ReWritable disk. They have a layer which can be either crystalline (which reflect light) or amorphous which scatters the light. When erasing a disk a higher power laser converts the amorphous areas back into the crystalline form. Not a very high signal to noise ratio and often only readable on other CD-RW machines. Original audio format devised by Philips and Sony - referred to as CD Digital Audio - CD-DA to the Red book standard. First computer CD-ROMs also defined by Philips and Sony to the Yellow book standard. Yellow book defines three standards: Mode 0 rarely used. Almost the same as CD-DA. Mode 1. CD-ROM (Mode 1) The data is held in blocks of 2352 bytes of which 2048 bytes, starting at the 17th byte, contain the important data. The 276 bytes at the end of the block contain codes which can be used for error correction in the main block. This gives an estimated error of 1 bit in 200 CDs! Mode 2. Rarely used, error correction coding sacrificed. Yellow book extended to give CD-ROM XA format. Most popular form CD-ROM XA (Mode 2) (Form1), even though it is different to the formal mode 2 format. The main difference in the software required to read CD-ROM (Mode 1) and CD-ROM XA (Mode 2) (Form1) is that the 2048 data bytes start on the 25th byte instead of the 17th byte. A system which will read CD-ROM XA (Mode 2) (Form1) will also read Philips CD-I and Kodak PhotoCDs. CD Extra format: written to the Blue book standard. Multi-media. Also called CD Plus and Enhanced CD. The audio tracks are laid down first in CD-DA format and the data track in CD-ROM XA (Mode 2) (Form1) format is laid down afterwards. Such disks can be played on standard CD players. A computer will read the last track first ©IPK30/04/17 Multi session. Works by writing a table of contents (TOC) to the disk at the end of the first session. In subsequent sessions files not in TOC or modified are written to the disk and a new TOC written. Since the software should read the last file first, the latest TOC will be read. Each session on a CD-R disk takes a lead in track of about 13Mb To make a CD autorun. Create a file in the CD root directory named autorun.inf In the file put [Autorun] open=application.exe icon=icon.ico The 'open=' shows the path and filename of the application to be launched when a disc is inserted and the 'icon=' lets you specify your own icon for the CD-ROM drive in Windows Explorer -CDF Channel Definition Format - developed by Microsoft. Describes the content and properties of Push channels using XML mark-up. -CDMA Code Division Multiple Access -CDO Collaboration Data Objects -CD-ROM ISO standard. ISO level 1 allows forfilenames of up to eight plus three characters. ISO level 2 allows for file names of up to 31 characters -CELP Code Excited Linear Predictor. Used for speech coding in VoIP -Centrex Central Office Exchange service is a type of PBX service where switching occurs at a carrier's local telephone exchange instead of at the company premises. -Centrino To get the Centrino badge a notebook must contain three components: the Intel Pentium-M processor, the Intel 855 family chipset and the Intel PRO/Wireless 2100 Network Connection. A 1.6GHz Centrino noetbook will always outperform a 2.4GHz Pentium 4-M notebook. The Pentium-M processor is like a combination of a Pentium-III-M and the Pentium 4M. The processor gets more performance per clock cycle (courtesy of the Pentium-III) and a quad pumped 400MHz front side bus and support for SIMD and SIMD2 instructions from the Pentium 4). The system also provides extended battery life. -CERNET Chinese Education and Research Network. -CGI scripts Common Gateway Interface. Small programs that run on a web server. -Characteristic Impedance The impedance that a channel would have if the channel were infinitely long. -Cheapernet See 10BASE2. Uses a thinner, lower cost cable. -CIDR Classless InterDomain Routing. Used for subnetting -CIELab an exact colour scale. ©IPK30/04/17 -CIFS Common Internet File System. Also referred to as SMB -CIM Common Interface Model -CIRC Cross Interleaved Reed-Solomon Code -CIS Card Information Structure. Information about a PCMCIA card that is passed to the host computer when the card is inserted -CIS Contact Image Sensor - employs dense banks of red, green and blue LEDs to produce white light and replace the mirrors and lenses of a CCD scanner with a single row of sensors placed extremely close to the source image. -CISC Complex Instruction Set Computer -CITRIX Supplier of client computing -CIW Certified Internet Webmaster -CiX Compulink Information Exchange -CLA Corporate License Agreement -CLEV CyberLink Eagle Vision. Used on Power DVD. Intelligently adjusts contrast and colour in a movie and balances darker and lighter areas. Makes hefty demands on hardware. -CLI Common Language Interface. Microsoft. -CLPV CyberLink Pano Vision. Used on Power DVD. Compensates for the problem of watching 4:3 aspect ratio films on a widescreen display by stretching the video at the screen edge, leaving the central part of the movie untouched. Also used on WinDVD -CLR Common Language Runtime - the heart of the .NET framework. -Client A Node on the network, such as a user workstation, that uses resources provided by the server -CLIP Caller Line Identification Presentation -Clusters (allocation units) Data is stored in clusters ranging from 2KB to 32KB, depending on disk size. -CLV Constant Linear Velocity. Used with CD ROM drives. Ensures that the data is read at a constant speed. Used on early CD ROM machines. -CMA Computer Misuse Act. ©IPK30/04/17 -CME Core Management Environment. Phoenix's replacement for BIOS. -CMYK cyan, magenta, yellow and keystone black. -CNR Communication and Network Riser -COAST Cache On A STick. Used to upgrade level 2 cache. -COBOL The first programming language for business use. Developed in 1960. -ColdFusion A development environment for building and deploying web applications and web services. Now part of the Adobe/Macromedia family and integrated with products such as Flash, Dreamweaver and Acrobat. First released by Allaire in 1995. Coldfusion has its own tag-based server-scripting language, Coldfusion Markup Language (CFML), with a syntax that closely resembles HTML and XML -Collaborative network Allows other users to share resources, i.e. processing power. Used in Exchange Server and SQL server -Collision The result of two stations attempting to use a shared transmission medium simultaneously. -Colossus Computer developed during WW2 by Tommy Flowers and used to crack German coded messages. Designed, built and installed in 9 months it contained 1500 valves. Ten were built and 8 were dismantled straight after the war. Two went to GCHQ and were subsequently dismantled in 1960. Tommy Flowers (1905 - 1998) was an engineer for the General Post Office (GPO) and after the war returned to the Post Office and worked on telephone exchanges. -COM Component Object Model - a means of communication between software objects. Microsoft. Provides inter application communications between software running on the same machine. e.g. a Word document can embed a live spreadsheet from Excel, or Internet Explorer can display a Powerpoint slide. -COMMAND.COM Interprets DOS commands. -Compact Flash Memory card. First released in 1994 - 3.3V and 5V supplies. 3.3mm thick. Type II cards are 5mm thick. These are primarily IBM microdrives. -Compiler Translates from a high level language to machine code. It produces an object code file. -Computer Misuse Act 1990 "Unauthorised access" refers to some-one bypassing a user name and password screen. Section 1: "A person is guilty of an offence if a). he causes a computer to perform any function with intent to secure access to any program or data held in any computer; b). the access he intends to secure is unauthorised; and ©IPK30/04/17 c). he knows at the time when he causes the computer to perform the function that that is the case. -CONFIG.SYS Stored in the root directory. A listing which tells the machine what hardware is installed, how to use the physical memory, which version of DOS, etc. It is the first file to be processed when the PC is turned on. DEVICE=C:\DOS\HIMEM.SYS Lets DOS know it can load some programsinto High Memory DEVICE=C:\DOS\EMM386.EXE XX lets DOS use all memory over 1Mb. If XX=RAM then memory can be used as both expanded and extended. If XX=NOEMS then PC told not to use expanded memory (may be needed by some programs). BUFFERS=15,0 Buffers are small (1K) chunks of memory which DOS can use to store information quickly Not really needed any more. FILES=50 The number of DOS files that can be open at any one time. DOS=HIGH Tells DOS to use high memory whenever possible. DOS=UMB Tells DOS to use Upper Memory Blocks. LASTDRIVE=G Should be used to tell the PC the name of the last drive on the system. FCBS=4,0 Specifies the number of File Control Blocks that DOS can use at any one time. Rarely used or needed now. DEVICEHIGH /L:1,23376 =C:\SBCD\DRV\SBIDE.SYS /V /D:MSCD001 /P:1E8,11 Tells the machine about the CD-ROM drive. COUNTRY=044, ,C:\DOS\COUNTRY.SYS Tells the system which country it is in. DEVICEHIGH /L:1,15792 =C;\DOS\DISPLAY.SYS CON=(EGA, ,1) Tells system to convert American characters to English. -Contention ratio The number of other users competing for bandwidth on a broadband connection. A contention ration of 50:1 means that the available bandwidth is shared with 49 other users. -Cookie A cookie is a message sent by a Web server to a browser, and is stored in a text file, usually called cookie.txt. The message is then sent back to the browser every time a new request is made while still on the site. When you move to another site, the cookie stays on the hard drive. When you return to the original web site the browser sends the cookie information back to the web server. Cookies are mostly used to identify users and create site visit statistics on types of browser, operating systems and popular pages. -Corba Common Object Request Broker Architecture -CoS Class of Service ©IPK30/04/17 -cPCI Compact Peripheral Component Interconnect. Concept behind Blade technology -CPE Customer Premise Equipment. -CPU speed Accessories - System tools - System info - Tools - Windows Report tool. -Cray A supercomputer. The T3E900 has 840 DEC Alpha processors running at 450MHz. Twenty CPUs have 512MB of memory each and the other 820 have 128MB, which makes a total of 115,200MB. It can perform 80,000 million calculations per second (80gigaflops). -C-Ret Colour Resolution Enhancement Technology. HPs half tone printing technology. Four levels of ink per pixel are possible. -CRM Customer Relationship Management -Cross linked files When two or more entries in the FAT refers to the same allocation units (clusters). -Crosstalk The unwanted transfer of a signal from one circuit, called the disturbing circuit, to another, called the disturbed circuit. -Cryptography The science of transforming data into an unreadable format by anyone who does not have the correct key. Converts plain text into cyphertext. There are two basic types of encryption, symmetric and asymmetric. Symmetric encryption uses the same key to encrypt and decrypt the cyphertext. Caesar cipher - substitution cipher. Letters are substituted for other letters in the alphabet. Can be done by shifting the letters by x places in the alphabet or by defining a completely new character map. Both methods redundant as they can be broken by checking the combinations. Basic Englishlanguage rules help 'e' is the most common letter, and the most common two-letter combinations are 'th', 'in', 'er', and 'an'. Knowing the subject of the cipher text also helps since specific words can then be sought. Transposition cipher - does not disguise the letters but rearranges them instead. First a word without repeated letters is used as a key. The number of letters in the word is used as the number of columns, with the columns numbered by the alphabetical position of each letter - 'a' equals 1 etc. The plain text is written in rows and the ciphertext produced by reading the columns in numerical order. To convert back the same operation is used in reverse, i.e. columns are populated in order. For this to work the number of columns has to be known so the correct number of characters can be put in each column. For the system to work the table has to be fully populated by putting random characters at the end of the plain text to fill out the table. To uncover the code you have to break the number the number of columns used as the key and then rearrange them until they make sense. e.g. N E T W O R K 3 1 6 7 4 5 2 h e a a e m t c r o i i e n o p s s n h a t o e d r f r ©IPK30/04/17 plain text ciphertext heresademionstrationofacipher emtcdrfrheaassnhatoeroiienop One-time pad - All encryption methods so far can be broken as they rely on simple character replacement that retains patterns. Perfect encryption that cannot be broken - called the one-time pad. This uses a randomly generated key that is the same bit-length as the plain text. An exclusiveor is then performed between each bit of the key and the plain text. Getting the plain text back uses the same procedure which is perfectly secure for two reasons. First, standard cryptographic attacks do not work because each letter is equally as likely to appear. Secondly, trying every single key combination in a brute-force attack does not work, as each decryption is as likely to be correct. This only holds out if the key is not divulged, and is only used once - hence the name. Theoretically, encrypting multiple pieces of data could lead to statistical attacks breaking the key. The problem with this is the key is unwieldy to carry around and cannot be memorised. Symmetric algorithms - uses smaller - 64-bit upwards-keys to encrypt the data. The XOR operation is fast and masks the contents of the packets so standard cryptographic attacks that rely on identifying patterns of data do not work. The key must remain a secret, as anyone who knows it can decrypt all of the data. These systems are called private-key encryption. RC4 and Data Encryption Standard (DES) are the most popular. The speed of the encryption makes them suitable for use in real-time applications such as VPNs. Asymmetric encryption - symmetric encryption suffers from the problem that it is difficult to distribute keys and any encrypted message can be read by all users with the key. Sometimes a message needs to be encrypted so only the intended recipient can see it. Asymmetric encryption developed in 1976 at Stanford University by Diffie and Hellman. The principle, also known as public-key cryptography, works on the assumption that instead of having a single key to encrypt and decrypt, there are two keys, one to encrypt and one to decrypt. The encryption key is known as the Public key and any user wanting to send a message can use it. The decryption key is the private key and the owner never divulges it. Any message encrypted with the public key can only be decrypted with the private key and is secure in transit as only the intended recipient can read it. There are no problems with key distribution as the public key is available and the private key is known only by the owner. The system has three requirements. Assume that 'm' is the message, 'E' is the public-key encryption algorithm and 'D' is the private-key decryption algorithm. The three requirements are: D(E9m)) = m anything that is encrypted with the public key can only be decrypted with the private key. So E(m)/E does NOT equal m It is extremely difficult to deduce D from E E cannot be broken by a chosen plain text attack. The most common public-key algorithm is named after its discoverers, Rivest, Shamir and Adleman (RSA). The algorithm works by finding two large (e.g. 1024-bit) prime numbers. The large prime numbers are used to create the two keys e.g. Take two large prime numbers, 'p' and 'q'. Calculate (p-1)(q-1). Choose 'd' so that it does not share any prime factors with (p-1)(q-1). 'd' does not have to be a prime itself, but it does have to be odd. Compute 'e' where de =1 (mod (p-1)(q-1)). Mod represents the remainder part of a division e.g. 3 mod 2 = 1. But it can also be used to describe a number in modulas form as denoted by brackets. eg 25 mod 12 = 1 and 25 = 1 (mod 12). The encryption algorithm is encrypt(m) = (me) mod pq, where 'm' is the plain text message and a positive integer. The decryption algorithm is decrypt(c) = (cd) mod pq. Therefore for encryption you need (pq, e), the public key. Decryption needs (pq,d), or the private key. eg (with small numbers!) Let p = 3 and q = 11 ©IPK30/04/17 (p - 1)(q - 1) = (3 - 1)(11 - 1) = 2 x 10 = 20 d has to be relatively prime to (p - 1)(q - 1) so 'd' has to be relatively prime to 20. Choose 'd' to be 7 as it does not share any prime factors to 20. de = 1 (mod ((p - 1)(q - 1)) 7e = 1 (mod 20) 7e mod 20 = 1 e=3 p x q = 3 x 11 = 33 This can be used to encode the plain text NETWORK. Plaintext(m) Char Numeric N 14 E 05 T 20 W 23 O 15 R 18 K 11 Ciphertext(c) m3 m3 mod 33 2744 5 125 26 8000 14 12167 23 3375 9 5832 24 1331 11 Decryption c7 78125 8031810176 105413504 3404825447 4782969 4586471424 19487171 c7 mod 33 14 05 20 23 15 18 11 Char N E T W O R K Due to the way the system works it can also be used for authentication. Digital signatures. First the sender creates the message and computes its checksum, which is encrypted using their private key. The message is encrypted using the recipient's public key and transmitted. When it arrives, the recipient decrypts the message using their private key, then decrypts the checksum using the sender's public key. If this works it proves the sender generated the message. Finally the checksum is recalculated to ensure the message has not been tampered with. -CSMA Carrier Sense Multiple Access. A technique by which many work stations can transmit over one cable without a controlling transmission authority -CSMA/CD CSMA with Collision Detection. CSMA that also listens while transmitting to detect collisions. Used in IEEE 802.3 Ethernet -CSS Cascading Style Sheet. Language developed to bring more control over screen presentation to HTML authors -CSS2 Content Scrambling System. Used on DVD audio -CTI Computer telephony Interface/Integration -CTRL * a b c drag a file End Esc Esc + r F4 F6 Select all Bold Copy to a folder to copy a file Goto end of document Displays the Start menu to open the Run dialog box Close current document Goto next open document ©IPK30/04/17 Home g i p s u v x z Goto beginning of document Goto option in Windows Explorer Italic Print Save Underline Paste Cut Undo Goto beginning of next word Goto beginning of previous word Goto beginning of next paragraph Goto beginning of previous paragraph C R T Del Inserts copyright symbol © (W97) Inserts registered trademark ® (W97) Inserts trade mark symbol ™ (W97) Close program options End F6 Home drag a file Select to end of document Goto previous open document Select to beginning of document Select word to the right Select word to the left Creates a shortcut to the file -CTRL ALT * -CTRL SHIFT * -CTS Computerised Telephone Systems -CVSD Continuous Variable Slope Delta modulation (CVSD) voice coding scheme. Even at a bit error rate of 4%, the CVSD coded voice is quite audible. -CWDM Coarse Wavelength Division Multiplexing. Has a channem spacing of 20nm. Can be used for distances up to 75km. To have speeds of 10Gb/s, the data is split into 4 x 3.125Gb/s feeds. The multiplexers are based on either a prism or a tilted Micro Lens Array (MLA). -Cyberspace Invented by science fiction writer William Gibson, who defined it as 'a graphical representation of data abstracted from the banks of every computer in the human system. It is the virtual universe of information transmitted by computers, programs, audio and video media, telephone, television, wire and satellite. DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD -DAFS Direct Access File system, a file sharing protocol designed to improve the performance of network-attached storage systems. -DAS Directed Attached Storage - a disk array directly connected via IDE or SCSI to a server for content storage ©IPK30/04/17 -DASP Dynamic Adaptive Speculative Preprocessor -DAT Digital Audio Tape. Two heads for reading and two for writing data. Information is recorded onmini cassettes using a helical scan which spools a 4mm tape at speeds of 0.32in/s. The angle of the tape head results in a high density of data, around 4Gb, more if DDS formating or DDS-2 data compression is used. -Data Protection Act 1998 Individuals have the right to view sensitive information about themselves e.g. sickness records, disciplinary and training records, appraisal notes, e-mail logs and general personal files. -DAX A unit used by BT at the exchange that allows a single wire to be used as a double line. Some reduction in quality but only half of the Internet speed. -DB2 Database software from IBM that runs primarily on Unix and Solaris platforms -DBA Data base Administrator - software which administers databases. It carries out the maintenance of a database, including the applications and content structure. -DBMS Database Management System. The program which builds the data base e.g. Access. -DCE Data Circuit-terminating Equipment e.g. a MODEM - fitted with a female connector. Data Communications Equipment. -DCOM Distributed Component Object Model. Within the Windows operating system - enables one application to communicate with another by exchanging data and providing services that can be invoked by other DCom-aware applications. DCom is the version of the Com protocol that extends inter application communication to external computers so that a client PC can call up a DCom-aware service running on a server -DDE Dynamic Data Exchange. Allows programs using OLE to exchange data dynamically. -DDI Direct Dial Inwards. -DDoS Distributed Denial of Service attack. Tribe FloodNet and Trin00, typical open source tools. -DDR RAM Double Data Rate RAM. Type of SDRAM in which data is sent on both the rising and falling edges of clock signals. Used on video cards. Supported by 760 chipset DDR technology and bus topologies have a maximum clock frequency of 200MHz, or 400Mb/s/pin. This is commonly referred to as DDR400 -DDR2 Starts where DDR ends. DDR2 supports clock frequencies of 266MHz (DDR2-533) and future speeds of 333MHz (DDR2-667). By running dual channels a potential throughput of 8.6Gbytes/s ©IPK30/04/17 To achieve the increase in clock speed, changes have been made to the architecture. The operating voltage has been lowered to 1.8V + 0.1V. All DDR2 components use an FBGA package instead of TSOP. On die termination is used to improve signal quality on the databus. Has 240 pins instead of the 184 pins of DDR. -DeCSS Algorithm for cracking CSS encryption. Also Speed Ripper -DECT Digital Enhanced Cordless Telecommunications phone. also Digital European Cordless Telephony. Operates within the 1.9GHz band and released for use in 1992 -DEN Directory Enabled Networking. Allows network managers to manage bandwidth and prioritise traffic. -DES Data Encryption Standard. Devised by IBM in and adopted by the US government in 1977. The best known example of secret key encryption. -Desktop icons To change Open Paint. New Select Pels as units and make picture 32 for both with and height. When complete save with double quotation marks as "newicon.ico". Windows sees the ICO extension and automatically creates a 16 bit colour icon, shrinking the image to fit as needed. To replace an icon, select through properties of the icon to change. -Device driver A piece of software that will let the operating system and programs running with it, control a particular hardware device such as a monitor or a printer. -DFS/DCS Dynamic Frequency Selection/Dynamic Channel Selection - allows client devices to detect the clearest channels within the radio waveband. See IEEE 802.11h. -DHCP Dynamic Host Configuration protocol. A DHCP enabled server automatically assigns internet protocol addresses to networked computers, so each networked PC doesn't need an individual IP address to access the Internet. -DHSS Direct Sequence Spread Spectrum -DHWG Digital Home Working Group. -DHTML Dynamic Hypertext Markup Language -Diffserv Differentiated Services. Used in VoIP. Overcomes the limitations of ToS. It is a layer-3 protocol used at the edge of an enterprise which tags each frame, either at the originating device or at an intermediate point, to identify the requested level of service. It includes a Differentiated Services Code Point (DSCP) which specifies how each switch handles the frame. -Digital Audio Type CD DVD Video DVD Audio Different formats. Resolution bit/sampling rate 16/44.1kHz 24/96kHz five channel 24/96kHz two channel 24/192kHz Audio bandwidth 20kHz 48kHz 48kHz 96kHz ©IPK30/04/17 HDCD SACD -Digital Radio 20/44.1kHz 1/2.8224MHz 20kHz 100kHz Broadcast at 256Kbps -Digital Telephony Usually an analogue signal is sampled every 125microseconds by an 8-bit ADC. Each telephone requires a 64Kbps channel. T-Carrier First digital network. Introduced in the 1960s in America. Based on a 1.544Mbps T-1 line. System still in use. The line is divided into 24 x 64Kbps channels for voice communication using Time Division Multiplexing. The channels are combined into one 192-bit frames plus an additional bit to separate frames. 8000 of these are transmitted per second. Control signals are sent by robbing 2-bits from the encoded voice signal. E-Carrier Used in Europe. Uses 2.048 Mbps E1 line giving 32 x 64Kbps voice channels. Does not use bit-robbing and uses the entire bandwidth for encoding the signal. Digital Signal X describes digital transmission rates based on DS0, which is 64Kbps. See ISDN, ADSL and DSL. DSX Comparison Digital Signal Data Rate DS0 multiple T-Carrier E-Carrier DS0 64Kbps 0 DS1 1.544Mbps 24 T-1 2.048Mbps 32 E1 DS1C 3.152Mbps 48 DS2 6.312Mbps 96 T-2 8.448Mbps 128 E2 34.368Mbps 512 E3 DS3 44.736Mbps 672 T-3 139.264Mbps 2048 E4 DS4/NA 139.264Mbps 2176 DS4 274.176Mbps 4032 565.148Mbps 8192 E5 -Digital Signal X See Digital Telephony -Digital TV Each frame is split up into around 300,000 pixels. Each pixel is assigned a code number made up of data bits that identify its position within the picture, its colour and its light intensity. Therefore about 600kB are needed per frame and about 18MB per second. Compression operates on the principle that there are multiple pixels within consequtive frames which are identical. So these do not have to be transmitted every frame. -Digital Video Formats Three main standards used by digital camcorders. DV25, MicroMV and DVD-VR. DV25 is the most common and is used by all consummer MiniDV camcorders. It uses a 5:1 compression that records video at a constant rate of 25Mbps. Requires around 13GB for an hour recording. It is tape based - but good for editing since all of the frames can be read individually. Tape based MicroMV uses MPEG-2 compression and records at 12Mbps. The data needed for a single frame of video may be spread across a series of frames so cross fades can require cross calculation and rendering. DVD-VR is another MPEG standard - data rate of typically 6Mbps. ©IPK30/04/17 -DIMM Dual In line Memory Module. A memory board that is effectively a double SIMM. It uses a 168 pin connector and its 64 bit wide bus allows single modules to be installed in Pentium systems. A memory module with signal and power pins on both the front and back of the board. -DirectX Video and sound card drivers. -DIS Digital Image Stabilisation. Used on camcorders to reduce camera shake. It works by looking at the detail around the edge of the frame to work out whether the image is shifting. Also OIS -Display adapters MDA Monochrome display adapter. Each character was displayed in a 9 x 14 grid, with 80 characters per line and 25 lines per screen CGA Colour graphics adapter. Each character was built on a 8 x 8 grid with maximum resolution of 640 x 200 (standard was 320 x 200). Four colours. EGA Monochrome text in 9 x 14 grid at resolutions of 720 x 350, but also CGA colours at 320 x 200. VGA 640 x 480 and 16 colours SVGA 600 x 800 at 256 colours -Distributed Computing Tasks completed locally on machines , not on server. -Dithering This is the process which uses dots in patterns to create different colours. -DIVx An implementation of MPEG4. It can compress video to a much greater extent than even MPEG2, while achieving much the same visual quality. Can support frame sizes up to 4096 x 4096 pixels and is able to deliver high-definition footage. -DLL Dynamic Link Library. A way of writing programs so that bits of them- the functions in the library- can be shared between several tasks at the same time rather than each task containing copies of the routines it uses. To register a .dll file c:\windows\system\regsvr32.exe file.dll. Most functions of the Windows API are made accessible by DLLs. Can be viewed by Quickview. -DLP Used in Data projectors. Largely the creation of Texas Instruments. The image is formed on the DMD (digital micromirror device) IC. The surface of this chip is made up of thousands of tiny rotating mirrors and each of these represents an individual pixel which can be rotated between an on and off position (10 - 12 degrees of rotation of the mirror are possible). Light is directed onto the surface of the DMD IC and, as it hits the mirrors, it is either reflected onto the screen or onto a light absorber. The image can appear fuzzy compared to LCD projectors but he contrast ratio is greater. -DLT Digital Linear Tape. Back-up tape format. The capacity of DLT tapes is currently 35GB per cartridge with a transfer speed of 5MB/s for the DLT7000 and 40GB per cartridge for the DLT8000. Super DLTs will be in service mid 2000 and will offer 100GB per cartridge with a transfer rate of 10 to 20MB/s. Super DLT uses Laser Guided Magnetic Recording ©IPK30/04/17 (LGMR), which employs optical and magnetic methods to greatly increase the data storage capacity of cartridges. SDLT 220 drives can fit up to 110GB (uncompressed) onto each tape with transfer speeds of 11MB/s. SDLT 320 drives can fit up to 160GB (uncompressed) onto each tape with transfer speeds of 16MB/s. -DLZ Digital Lempel Ziv - a compression system used on back up tapes. -DMA Direct Memory Access. A process for data retrieval from a device such as a hard drive that writes it into main memory without involving the processor, so freeing it up for other tasks. -DMFC Direct Methanol Fuel Cells -DMI Desktop Management Interface. -DMT Differential Mode Termination is a way of terminating a modular connector or cable in its characteristic impedance. -DMTF Desktop management task Force -DNA Distributed iNternet Architecture Developed by Microsoft in 1998. -DNS Domain Naming System. This is the system that turns the numeric data that the Internet uses for web site locations into text the user can use, e.g. 128.125.0.0 = jmc.ac.uk The DNS is implemented as a hierarchical system of communicating nameservers. Currently based on IP version 4 (IPv4) which gives the dotted quad numbers and has values in the range 0 to 232 (four and a bit billion). DNS entries in DNS server data bases include: Resource Records (RR) which define the mapping between names and addresses. The following five types of RRs are most common. Address Records (A) the name to address record which tells you that sooty.korana.com is 139.243.12.1 sooty.korana.com IN A 139.243.12.1 One name can point to several different IPs which can be useful when running a web service and there is a need to load balance. (IN means that it is defining an internet address.) www.korana.com IN A 139.243.12.1 www.korana.com IN A 139.243.12.7 www.korana.com IN A 139.223.34.54 Canonical Name Records (CNAME) is a way of defining aliases for a name. eg if the FTP server is sooty but we want it accessible as ftp.korana.com, the CNAME record allows this. ftp.korana.com IN CNAME sooty It is best not to have a CNAME pointing to another CNAME but to an A name. Mail Exchange Records (MX) used for e-mails. The local mail server has to find the identity of the machine that handles mail for that domain, so takes everything to the right of the @ sign and looks up the MX record for that address. mail.korana.com IN A 139.243.12.11 korana.com IN MX 10 mail korana.com korana.com IN MX 20 mail someisp.com The extra number specifies the order of preference. Useful to have a backup mail server. ©IPK30/04/17 Nameserver Records (NS) used to delegate the responsibility of looking after part of the domain to some other DNS. ns1.research.korana.com IN A 194.75.187.34 ns2.research.korana.com IN A 194.72.122.4 research.korana.com IN NS ns1.research.korana.com research.korana.com IN NS ns2.research.korana.com Reverse Mapping Records (PTR) used to take an address and map it onto a name. To look up the name that corresponds with the address 139.243.12.1, you reverse the order of the numbers and put in-addr.arpa on the end. So in the DNS configuration file there would need to be 1.12.243.139.in-addr.arpa IN PTR sooty.korana.com There are other RRs but they are not generally used including HINFO. For IPv6 there is a different RR, the AAAA record. V6test.korana.com IN AAAAABDE::FE:22DC:FFDE:CAD2 Reverse addressing with IPv6 use the ip6.int instead of in-addr.arpa and separate numbers by dots instead of colons 2.D.A.C.E.D.F.F.C.D.2.2.E.F.0.0.0.0.0.0.0.0.0.0.0.0.E.D.B.A.ip6.int. IN PTR v6test.korana.com (all on one line) $ORIGIN used to simplify writing IPv6 IPs. $ORIGIN used to define a string of numbers which are then added to all numbers that follow unless they are followed by a dot. http://sunsite.org.uk/rfc/ -DOM Document Object Model. See XML -Domain On an NT network, a collection of computers with a common account database. The account database resides on a server called a Domain Controller. In W2K and later releases, Active Directory works by creating domains within a company. A domain is defined by a security boundary, and can span several physical sites. -Domain Controller A .net Server operating system responsible for controlling a local domain. A Windows server responsible for controlling a local domain. -Domain Registries .uk .com .net .biz .org .info Nominet VeriSign Verisign NeuLevel Registry Afilias www.nominet.net www.icann.com www.internic.net www.internetters.co.uk -DOS and Win3.1 can only use 64MB of memory. .COM files executed before .EXE files. Too many files in a directory can slow performance, keep to less than 150. dir switches, /o:n the /o:n is a switch to order the files by name. /p pauses the screen until a key is pressed. /w displays the list in wide format. ©IPK30/04/17 /o:d displays files in order of date. TREE all directories and files on the disk are displayed; switches (vert. line) MORE displays the tree one screen at a time until a key is pressed. /f scrolls directories and all its files. Including a specific filename after the CHKDSK command checks that particular files for fragmentation. CHKDSK has two switches; /F fixes the lost units and gives the opportunity to save each to a file for examination. /V displays the name of each file in every directory checked on the disk. Only run CHKDSK from DOS or it can corrupt files. CHKDSK will report but not fix cross linked files. To direct the output of CHKDSK to a file named INFO.TXT, type CHKDSK C: >INFO.TXT. To run SCANDISK type HELP SCANDISK at the command prompt. XCOPY32 enables long file names to be copied. Useful for copying one hard drive to another. eg.xcopy c:\*.* /e/h/k/r d: where d: is the drive letter of the new disk To boot up into DOS instead of windows. From a DOS prompt type atrib -s -h msdos.sys and then edit msdos.sys. Look for the line that says BootGUI=1 and change the 1 to a 0. Finally save the file. The system will now boot to a C prompt whenever you start up. Then type win to start windows 95. List of DOS commands available in Win95 Resource kit. Look for Win95rk.hlp file in the Admin/Reskit/Helpfile directory. Open using Explorer. DOS from Windows. The configuration files used when you restart Win95 in MS-DOS mode are determined by the properties of the 'Exit to MS-DOS' shortcut in the Windows folder. Locate using explorer, right click and choose Properties. Click program tab and click Advanced button. If 'Use current configuration' is selected, Windows will run the file dosstart.bat (in the windows folder) when dos starts. If 'Specify a new MS-DOS configuration' then you can create a new config.sys and autoexec.bat files for MS-DOS mode. DIR<LPT1 generates a directory list of file names and sends it to your printer. PROMPT=$p$g defines the appearance of the DOS prompt. By default you get the current drive and a greater than sign. $p adds the current directory path -DOS Commands ipconfig /? ping /? route print tracert url or IP -DRAM Accessed through the command prompt. ip configuration provides available routes from your machine. short for Trace Route. Traces the route to another system Dynamic Random Access Memory. -Driver files Located in C:\windows\system, and c:\windows\inf, and c:\windows\help files. Copy all into a new folder c:\drivers. Can reinstall all drivers from this directory -DRM Digital Rights Management. Protects ownership, privacy, owners as content travels from creator to distributor to consumer. ©IPK30/04/17 -DSD Distance Selling Directive. A retailer must provide the following details before a sale: seller identity, price of goods, delivery costs, arrangements for payment and delivery. After the sale the retailer must provide written confirmation of the order. Still have 7 days to change your mind, cancel the order, and send it back. If the retailer fails to provide written information on terms and conditions then you have 3 months to return the goods, but everything must be returned unused. If the goods do not work the supplier legally has to offer you a full refund and take the faulty goods back at no further cost to you. In the case of any return of goods the money must be refunded within 30 days. The directive also states that consumers can cancel credit card payments and be fully refunded by the card issuer, in case of fraudulent use. -DSD Direct Stream Digital encoding - used on SACD -DSI Dynamic Systems Initiative - from Microsoft -DSL2 Downloadable Sounds Level 2 -DSL Digital Subscriber Line. Uses the existing copper cables to transmit data. SDSL has the same up-link and down link speeds. ADSL often has a 512Kbps downlink and a 256Kbps up-link speed. ADSL transmits data at a high frequency above the normal frequency band of speech. Speech and Data can therefore go down the same line at the same time. The ANSI standard for ADSL uses Discrete Multi-Tone (DMT) a type of frequency division multiplexing. DMT takes the high frequency part of the line and divides it up into 247 channels, each 4kHz wide. These are known as Tones. The system monitors each channel and shifts the signal between channels to get the best signal for transmission and reception. Specific equipment needed for this. On the Telco side a DSL Access Multiplexer (DSLAM) takes all incoming connections and sends them on a pipe to the Internet. For DSL the cable is not shared unlike the system used by cable companies which do share. At the client end an DSL modem is needed which combines a splitter to allow voice as well as data. -DSO Exploits Data Source Object Exploits. Tracking software. Often the registry entries for such tracking is not corrected by programs like Spybot. To change the registry entries find the path from Spybot. Typical might be: HKEY_USERS\S-1-5-18\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\)\1004!=W=3 After opening zones and clicking on ‘0’ look in the right window, under ‘name’ is the key ‘1004’ and the type is REG_SZ. Right click and delete this REG_SZ value. Then tight click and create a new DWORD Value, name it 1004. Right click on this new DWORD Value and goto modify. With protection removed (default) the DWORD Value is 0. With protection applied the value should be set to a Hex value of 3 (preffered). To be prompted, the value could be set to hex value 1. It may also be necessary to do the same for key 1001. -DSSSL Document Style Semantics and Specification Language. Modern version of SGML. -DSU Data Service Unit -DTCP-IP Digital Transmission Content Protection over Internet Protocol - an alternative to DRM. ©IPK30/04/17 -DTD Document Type Definition - a set of rules for tag syntax. -DTE Data terminal equipment. Computers and terminals are examples. -DTDS Disaster Tolerant Disk System. Data distributed in different physical locations. -DTMF Dual-Tone Multiple Frequency. The audio signalling frequency on touchtone phones. -DTT Digital Terrestrial Television -DUN Dial Up Networking. -DV Digital Video. European PAL resolution - 720x576. -DVD Digital Versatile Disk. RAM disks store 4.37GB (not 4.7GB) on a single side and 9.4GB double sided. The spin speed of a DVD is much lower than that of a CD but a 6 speed DVD achieves about the same sustained data transfer rate as a 32 speed CD ROM. DVD tweak sites www.uk-dvd.net www.7thzone.com alt.video.dvd.tech rec.video.dvd.players www.dvdangle.com Dual layered DVDs known as DVD9, single layered DVDs known as DVD5 The pits of DVDs are spaced 740nm apart. Also see CLPV and CLEV -DVD-Audio The specification was released in March 1999. Uses a sample size of 24 bits and a sample rate of 192kHz. Can record an audio signal with a frequency range of 0 to 96kHz and a dynamic range of 144dB. Can store up to 17Gbytes of data on a double sided dual layer disk and can have up to 6 audio channels. Uses a PCM system. (Cf a CD, 16bit, 44.1kHz sample rate, recording 5 to 20kHz with a dynamic range of 96dB on a 650MB disk) -DVI Digital Video Interface. Replaces the RGB socket allowing flat panels and projectors to be connected. There is no conversion loss between analogue and digital so picture is better. Delivers a digital signal from the graphics card to the monitor -DWDM Dense Wavelength Division Multiplexing. The use of additional wavelengths of laser light (different frequencies) adds extra capacity on the cable without having to change the cable. Current technology supports up to 240 simultaneous channels. DWDM is bit-rate and protocol independent. Uses temperature-controlled distributed feedback (DFB) lasers and have extremely tight channel spacing of 0.4 or 0.8nm. EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE -EAP -EARG Extensible Authentication Protocol Electronic Attack Response Group. Part of UNIRAS. Provides direct assistance to government departments experiencing an electronic attack. ©IPK30/04/17 -Easter Eggs A hidden program within a main application. Excel 97. New workbook select Edit, GoTo and type X97:L97 in the Reference field and click Enter. press the Tab key and then Ctrl, Shift and click the Chart Wizard button in the toolbar. Animated landscape - left mouse button forward and right on backwards. A stone pyramid is there with the credits of the programs writers. Esc returns top the worksheet. -E-Carrier See Digital Telephony -ECHR European Convention of Human Rights. -Eclipse An open source initiative aiming to provide a supplier-neutral software development platform. Eclipse.org was formed in 2001 by IBM, Borland, Merant, Red Hat, SuSE and others. In 2004 Eclipse became a not for profit corporation. It is written in Java and comes with plug-in construction toolkits. -ECM Enterprise Content Management -ECP Extended Capabilities Port. An improved parallel port which transfers data at over 2MBps and is bi-directional in operation. ECP mode primarily designed for devices such as ZIP drives. -EDAP Extended Data Availability and Protection. Now emphasised by RAB -EDGE Enhanced Data GSM Environment. -EDI Electronic Data Interchange. -EDO Extended Data Out. To read a word of computer memory it must be precharged first. EDO memory speeds up this sequence by precharging the next word while still reading the current word. -EFI Extensible Firmware Interface. Intel's replacement for BIOS. -EFMA Ethermet in the First Mile Alliance. Connections to WANs and the Internet. -EFS Encrypting File System. W2000 and XP Pro - encrypts the whole hard disk. -EFT Electronic Fund Transfer. -EIA Electronics Industries Association. An USA trade organisation that issues its own standards and contributes to ANSI; developed RS232 and EIA-568, a much used building wiring standard. -EIA 485 Specifies the electrical characteristics of generators and receivers for use in balanced digital multiport systems ©IPK30/04/17 -EIA 568A Colour code for 10Base-T. -EICAR European Institute for Computer Antivirus Research. Antivirus programs should be able to detect the following file as a virus, when saved as eicar.com x5o!p%@ap[4\pzx54(p^)7cc)7}$eicar-standard-antivirus-test-file!$h+h* -EIDE Enhanced Integrated Drive Electronics. This describes the electronics used to run large hard drives on modern computers. Also known as Fast ATA or High Performance ATA. An EIDE controller can handle up to four hard drives etc at a time. Enhanced IDE faster than IDE and allows disks larger than 528MB to be directly accessed. Max disk size 8.4GB, transfer rates up to 16MB/s and four drives can be connected to one adaptor. See UDMA -EIM Enterprise Instant Messaging -EISA Extended ISA slots. 32 bit slot running at 8MHz. -ELFEXT Equal Level Far End Cross Talk. -E-mail Servers and mail readers only need to be able to handle messages of up to 60KB. E-mail disclaimer: To alert the recipient that the e-mail may not be the whole story. Should inform recipients that e-mails may be monitored or stored. (Issue of personal e-mails) Should be at the top of all e-mails not bottom. Should say that contracts can only be concluded in writing. Should disclaim liability from acts or opinions that the company would not have sanctioned. -EMF (In printing) Enhanced Meta File -EMM Expanded Memory Manager. A utility allowing DOS programs to access memory above the 1MB limit that constrained earlier versions of DOS. The most common example is EMM386, included with DOS 5.0 and above. Windows 95/98 have built in memory management and don't need EMM. -Emoticon Or smiley is a set of keyboard characters used in e-mails to denote joking, sarcasm etc. eg :( indicates a joke, :) unhappiness. -EMS -Encryption Enhanced Messaging Service. Coding information in a way that makes it difficult to decode without either a key (cipher) or an awful lot of mathematical muscle. The longer the length of the cipher (in bits), the more difficult it will be to break. Two main types, symmetrical and asymmetrical. Symmetrical uses the same cipher to encrypt and decrypt data. Methods are based on mathematical algorithms. One of the first (mid 1970s) was the Data Encryption Standard (DES), an encryption algorithm using a 56 bit cipher. DES was at one time considered strong enough to be used for banks' automatic teller machines, but as computer power has increase it was replaced by triple DES, which ran the same piece of data through the DES algorithm three times for extra strength. Towards the end of the 1980s, a new encryption standard called AES (Advanced Encryption Standard) was developed and was established in 2001. ©IPK30/04/17 Symmetric encryption has the problem of getting the cipher securely to the other person. This is where asymmetric or Public Key Encryption (PKE) comes in. PKE uses two keys: a private one and a public one. If one key is used to encrypt, the other will decrypt. If A wants to send a message to B, it uses B's public key (which is available to everyone), to encrypt the message. Once it is encrypted, the only thing that can decrypt the message is B's private key, to which only it has access. The original developers of this technology formed RSA Security. Symmetric key encryption is always faster than asymmetric. Whereas AES uses a minimum cipher length of 128 bits, the RSA algorithm starts at 1024 bits. An alternative to the RSA algorithm is elliptical curve cryptography, which works with 160 bits and can be a useful form of asymmetrical key encryption on resource constrained devices such as PDAs and smart phones. Digital signatures provide a way of enabling people to "sign" their ciphers and messages in order to validate that the message is from who it says it is. Company A creates its digital signatures using its private keys. As before, it encrypts the message that it wants to send using a symmetrical algorithm (quicker than asymmetric one), and then encrypts the cipher for the message using B's public key. But then it also runs the unencrypted message through a mathematical algorithm called a hashing function, which produces a unique short string of characters. It then encrypts this string (known as a hash) with its own private key. Everything is then sent to B. B then uses its private key to decrypt the symmetrical cipher, which it then uses to decrypt A's message. But it then uses A's public key to decrypt the hash string. It runs the decrypted message through the same algorithm that A used to create the hash. If B's hash matches A's then it knows two things: first that the message has not been tampered with en route. Second, that the message definitely came from A because it was decrypted using A's public key, which means it must have been encrypted using its private key. Hashing algorithms come in various forms: MD5 is still used in many systems. SHA-1, created by the National Security Agency in the mid 1990s has largely superseded MD5. PKE had a major challenge, which was to verify that people's private and public keys were not being created fraudulently. Trusted certificate authorities (e.g. Verisign) were set up to help govern the creation of keys in what became known as Public Key Infrastructures (PKIs). Within a PKI, a certificate authority would create and sign company A's key to verify it. Take up was slow and difficult to use. To counter this PKI advocates often quote public key technologies such as Secure Socket Layer (SSL) or its successor, Transport Layer Security (TSL), which provides the padlock icon seen in secure browser sessions. These require no authentication of the user, but were there simply to authenticate the server and secure transactions. PGP, an open public key encryption software tool developed in 1991 by Phil Zimmerman. PGP is significant because it offered an alternative to top down certificate authority model used in PKI. For PGP, certificate authorities are replaced by trusted individuals, who endorse other peoples keys by signing them, leading to the phenomenon of key-signing parties. -Enterprise network Up to 500 users -EPG Electronic Programme Guide. Lists programs on TV and enables complex recordings to be made -EPIC Explicitly Parallel Instruction Computing - as used on Intel's 64-bit Itanium family -EPOC An operating system for mobile devices including phones developed by a consortium of companies (Psion, Phillips, Nokia, Matsushita). It goes further than WAP in ©IPK30/04/17 offering colour graphics, sound and rich text. It also allows developers to design their own interfaces unlike the rival Windows CE. -EPP Enhanced Parallel Port. Data transfers of 2MBps and bi-directional. Used mainly by printer monitoring software. -ERDRP Eligibility Requirements Dispute Resolution Policy -ERM Employee Relationship Management -ERM Enterprise Rights Management. Software which allows organisations to establish and enforce policies regarding who can do what with electronic messages and enterprise content. -ERP Enterprise Resource Planning -ESSID Extended Service Set ID - effectively the name for WLANs -Ethernet An IEEE standard developed first by Xerox and then sponsored by Xerox, Intel and DEC. Does not matter whether it is arranged as a Star or a Bus. Uses CSMA/CD as the data transmission protocol. Ethernet only has a useful capacity of 45% utilisation and a theoretical limit of 60%. Developed at Xerox Parc by Bob Metcalfe and David Boggs in 1973. Metcalfe was looking for a way to connect Xerox's Alto PC to a printer and came up with a cabling infrastructure that enabled multiple devices to be connected and new devices added on a single wire. In 1976 Metcalfe published Ethernet: Distributed Packet Switching for Local Computer Networks Originally devised by Bob Metcalfe at the Xerox Palo Alto research centre. Originally ran at 2.94Mbps but later (1983) internationally defined as the 10Mbps 802.3 standard. Conceived as a technology to join together multiple computers over a shared medium. Originally done using 10base 2 coaxial cabling - 50 ohm coaxial cable. Multiple stations transmitting at the same time cause collisions. To avoid this, Ethernet uses a Carrier Sense Multiple Access/Collision Detection (CSMA/CD) algorithm. Later Metcalfe left Xerox in 1979 and formed 3Com. In 1997, the IEEE finalised the 802.3u standard which is the 100Base-T standard or fast Ethernet. 1998, the IEEE defines the standard for gigabit Ethernet over fibre. 2002, the standard for 10Gb Ethernet is expected to be ratified. CSMA is used to detect when the medium is free. When it is, a station will transmit. If the medium is busy then it waits for it to become free. There are two main algorithms to perform this: 1persistent CSMA and non-resistant CSMA. The 1-persistent CSMA monitors the channel until it is free. It is called 1-persistent because a station will transmit with a probability of 1 when the channel is free. If a lot of stations are waiting then a collision will occur the moment the line is free. This means that collisions are more likely when the load is high. Non-resistant CSMA waits for the line to become free and then waits an additional random amount of time before transmitting. This is slower than 1-persistent but more efficient at high loads. Ethernet used the 1-persistent model. So when collisions happen because of two stations transmitting at the same time, both transmitting stations stop and wait a random amount of time before starting to transmit again. The random time interval ensures that the same collision does not happen repeatedly. Collision detection has three main concepts: collision window, frame size and collision back-off. The collision window specifies the amount of time that a transmission is vulnerable to collisions after the transmission has started. Caused by the physical distance between the machines and the ©IPK30/04/17 speed of electrical or light transmission. Consider two machines, A and B, on a long cable. If machine A starts transmitting, there will be a delay before the signal will hit machine B. If this delay is sufficiently long that machine B decides that the channel is free and so starts transmitting then a collision will occur. Frame size: As a station is barred from transmitting when another is already transmitting, Ethernet defines a maximum transmission size of 1518 bytes on all frames transmitted. There is also a minimum frame size of 64 bytes in order to ensure that there is always time for a station to detect a collision before it finishes transmitting. After transmission all stations have to remain silent for 9.6ms. This interpacket gap is used to allow circuits to recover and reset in time for the next transmission. Collision back-off: when a collision is detected, the transmitting station 'floods' the network. This ensures that all systems on a segment detect the collision. The 802.3 Ethernet frame format is shown in the diagram below. bytes 7 preamble 1 2 or 6 2 or 6 2 destination source address address start of delimiter length of data field 0 - 1500 data 0 - 46 pad 4 checksum Preamble: the seven byte field contains the pattern 10101010 seven times. It produces a 10MHz square wave in the Manchester Biphase encoding scheme, which is used to physically put data on the wire. This information is sued to synchronise the receiving station with the transmitting one. Start of frame delimiter: Defines the actual start of the frame. It contains eight bits transmitting the pattern 10101011. Destination and Source addresses: These are either two or six bytes long (16 or 48 bits). The destination address is looked at by all receiving stations. If the destination address does not match the local settings, the frame is discarded. The source address is used so that replies can be sent back. There are two standard lengths for Ethernet addresses, though the industry has mainly settled on the 48 bit standard. This is usually known as the Medium Access Control (MAC) address, which is hardwired into the NICs. Usually represented by six hex numbers e.g. 00 FD 4D 43 23 87 Length of data: Defines the length of the data in a packet. Minimum value of 0 and a maximum value of 1500. Because the Ethernet standard states that the minimum length of a packet must be at least 64 bytes long, including all of the other components in the frame, this means that the minimum length of the data field has to be at least 46 bytes. (See Pad below) Data: This field can be from 0 to 1500 bytes long. It contains the actual data that is being transmitted. When an IP frame is being sent over an Ethernet network, it is stored in this portion of the frame. Pad: This is used to push the size of the frame up to the minimum length of 64 bytes if the data field is not long enough. Checksum: This four-byte field contains a checksum for the Ethernet package. It allows the receiving station to check that the contents of the frame have not been damaged in transmission. IP on Ethernet: Devices sitting on an Ethernet network only understand Ethernet addresses. For IP to work in an environment such as this there has to be a method of finding out which IP address belongs to which Ethernet address. This is the task of ARP or Address Resolution Protocol. -Ethnographer Study the way humans relate with technology -ETSI European Telecommunications Standards Institute ©IPK30/04/17 -EVC Ethernet Virtual Network. -Even parity Data verification method in which each character must have an even number of "1" bits -Executable code The compiled and linked version of the object code. Contains all that is required to execute it within the operating environment. -EXIF A standard way of including extra information about an image with the file for a camera. www.exif.org -Extended Memory Any memory beyond the 1MB of the original PCs. Also known as XMS -extract.exe Used to extract files from CAB files on Windows CDs. The extract command searches all the consecutively numbered cabinet files starting with the one you specify. It is not necessary to know which cabinet file contains the file to be restored. extract /A win 9x_??.cab filename.ext /L c:\location to which it is to be restored. ??.cab is the lowest numbered .cab file -Extranet A web site that is a closed community protected by a password and/or firewalls. It is typically provided by businesses for suppliers, key customers etc. FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF -Fast ATA-2 A hard drive standard that transfers up to 16.6MB/s. Also incorporates modes as IDE Mode 4 and Multiword DMA Mode 2. -FAT File Allocation Table. This is a feature of the MS-DOS operating system that keeps track of what's where on disks. This is the only means DOS can use to find data on a disk. DOS doesn't necessarily store programs and data in consecutive chunks on the disk, instead taking the next available cluster. It is the FAT that maintains the link addresses for subsequent but physically separated clusters. Using 16bit addresses it can only support disks up to 2GB. FAT 32 uses 32 bit addressing and supports hard disks up to 2TB. -Fatal exception Generated by the Windows operating system when it detects invalid code, invalid data or illegal instructions being accessed by a program. Generally requires a restart to clear it. -Fatal exception OE Usually occur when Win95/98 encounters errors in the Registry. -Fax Fastest fax speed is 14.4kbps but most work at 9.6kbps. -FC-AL Fibre Channel Arbitrated Loop. A high performance drive interface, as used by high end SCSI drives. Data transfer rates of up to 200MB/s are supported. A storage protocol based on Token Ring and FDDI. -FCIA Fibre Channel Industry Association ©IPK30/04/17 -FCIP Fibre Channel over IP. A SAN interconnect protocol -FCPGA Flip Chip Pin Grid Array. Used on later PIIIs The flip chip designation referred to the fact that the processor core is situated at the top rather than the bottom of the chip -FC-PH Fibre Channel Physical Layer -FC-SCSI Fibre Channel SCSI. Used on SANS. -FDDI Fibre Distributed Data Interface. A token passing ring network specification developed by ANSI, implementing dual optical fibre rings. -Fdisk Run from floppy. First option is to 'Create a DOS partition or logical DOS drive'. Select Yes. Then 'Create Primary DOS Partition'. Usual to choose maximum space available. After the message 'Primary DOS Partition created' appears use Esc to return to main menu. Select 'Create extended DOS Partition' and then 'Create Logical DOS Drive(s) in the Extended DOS Partition'. Fdisk supplies the corresponding values until the entire hard drive has been assigned. Use ESC to return to main menu and choose 'Set active partition'. Select the primary partition, which now becomes the C drive. Press ESC twice to exit Fdisk. -Fdisk/MBR, sys c: -FDPT -FDX To Fdisk the Master boot Region of a hard disk? Fixed Disk Parameter Table. Full Duplex. Simultaneous, two way, independent transmission in both directions. -FEC Forward Error Correction.. A mathematical method of encoding data so that errors can be detected and corrected on receipt. It is unidirectional, i.e. there is no need for feedback from receiver to transmitter to indicate errors or request re transmission - the decoder in the receiver performs all detection and correction. -FedCIRC Federal Computer Incident Response Centre. Monitors malicious attacks on federal systems. -FEI Federation of the Electronics Industry -FEXT Far End Cross Talk -FHSS Frequency Hopping Spread Spectrum -Fibre Channel Used with Storage Area Networks (SANs). It is a combination of other standards including FDDI, SCSI, HIPPI and IPI. Offers the best of Channels (point to point) and networks (an aggregation of hosts) through the Fabric. Hosts only have to monitor their own point to point connection to the Fabric. This reduces the overhead placed on the host and allows transfer speeds of up to 2Gbps. Fibre Channel offers a fast and reliable transmission platform. A single mode fibre and longwave light source allows data to be transmitted 10km at 1Gbps. ©IPK30/04/17 The protocol is defined in a similar way to the OSI 7-layer model, though Fibre Channel only has five layers. Channels FC-4 IPI SCSI Networks HIPPI SBCCS 802.2 FC-3 common services FC-2 framing protocol/flow control FC-1 encode/decode FC-0 133 Mbps 266 Mbps 531 Mbps IP ATM FC-FH 1062 Mbps 2124 Mbps FC-0 layer - provides the physical link including the fibre, connectors etc FC-1 layer - defines the transmission protocol. It is responsible for serial transmission and encoding and decoding data. The system is similar to FDDI but uses a 10-bit transmission code as opposed to the 5-bit code used by FDDI. Data is encoded 8-bits at a time into the transmission character. Some redundancy allows some recovery in the event of an error. FC-2 layer - Defines the frame layout and header formats and serves as the transport mechanism. The layer is made up of a set of building blocks used to transfer data across a link. These are: Ordered Sets - are 4-byte transmission words that have a special meaning, e.g. start and end of frame delimiters, Idle (node ready for transmission and reception) and Receiver Ready (interface buffer can accept more frames. Frames - used to contain the data transmitted and have a max. length of 2048 bytes. Frames can also be used to send messages including acknowledgements and rejections. The Fabric has to accept frames from the source port and route them to the destination port. This layer is also responsible for splitting the data into frames and reassembling them at the other end. Sequence - a collection of related frames in transmission. Each frame is labelled with a unique sequence number so that they can be reassembled in the correct order at the destination end. Also used for error control to make sure that all of the data has arrived. Exchange - one or more sequences for a single operation. Can be uni or bi directional, but only one sequence can be in operation at a time. Protocol - defines the service offered. Includes Fabric logon and data transfer. Flow Control - Part of the job of this layer is to provide adequate flow control. Achieved by sending control frames. When a receiver's buffer is full, a Busy frame is sent over the network. This causes the transmitter to back off until the receiver is ready. Service classes - Three possible. Circuit switching with guaranteed delivery in order which is used by data channels: Packet switching with guaranteed delivery. Packet switching without guaranteed delivery. FC-3 layer - provides common features for advanced features including: Striping - this multiplies bandwidth by using multiple ports in a large pipe Hunt groups - allows multiple ports to respond to the same alias address. Multicast - lets one transmission be delivered to multiple addresses. FC-4 layer - Defines the application interfaces that can be run. The list of supported protocols is:HIPPI, IPI, SCSI, ATM, IP. ©IPK30/04/17 A special network card has to be installed into the host and gives the host a physical address and allows them to hook into the fabric. Hosts include servers, clients, tape libraries, disk drive arrays etc. Once a client machine connects to the Fabric it can access storage on any other machine subject to permissions. These can be placed many kilometres apart and so some could be effectively off site -Fibre Optic Cables Tube and Tight Buffer. Cables containing optical fibres. Two main types; Loose -Field Column in a database table. -File associations To associate a file Hold down Shift and then right click. Select Open With. etc -File extensions .bat Batch file .cnt Help content files .gid Global index files created by Win95 Help program .pps Microsoft Power Point .pst Outlook files .syd Backup file when changes made using Sysedit To open a pre-registered file with a different program - right click while holding the shift key. Select open with then click Always Use this Program to open these files. List of extensions at www.dmccabe.uklinux.net/update2/filextensions.html Extensions to delete: C:\Windows\temp any files older than a day. *.Backup files created by Windows ~$*.doc Temporary word files left after a crash. *.bak Backup files from various applications *.cab Installation files *.chk Files created by scan disk and chkdsk *.fts Windows will create these if it needs them. *.gid Windows will create these if it needs them *.log Log files delete if more than a few days old *.old Old versions of files *.prv Log files created by past Windows boots. *.shs Scrap objects - temporary files created in OLE supporting applications *.tmp Temporary files *.wbk Word backup files. -File Server -File type Stores files for users but does no processing. Three letter extension to the file name. To change a file type's association open Windows explorer and right click a file of the type you want to change. Right click the file and select Properties. Note the Type, click OK. Now select View, Option, and click the File Types tab. An alphabetical list of Registered file types on the computer is shown. Double click the file type to be changed (noted earlier). The Edit file Type dialog box appears and in the Actions list double click Open. Another Dialogue box appears. In the 'Application used to perform action' field, enter the path and filename (enclosed in quotes) of the application you want the file to be opened in. Use the Browse button to find the full path. Click OK. Click Close a couple of times. ©IPK30/04/17 To associate a file type with more than one application, before clicking Close, in the File Type dialog box, click the New button. A small dialogue box appears for adding another action to the file type. In the Action field, type an easily recognised name for the new application. In the 'Application used to perform action' field enter the program's path and file name. Click OK or Close until reaching the desktop. If a file is right clicked a choice is available as to what to launch the application with. -File virus Infects program (exe and com) files. Each time the program is run it copies itself. -Firewall A system designed to prevent unauthorised access to a network, particularly from hackers. All information entering or leaving a network is scrutinised, and rejected if it fails to meet security criteria. The first commercial firewall product was DEC's Secure External Access Link, released in 1991. Others quickly followed but the market took off in 1994 with Checkpoint's Firewall-1, the first product with a simplified icon and mouse user interface. -Firewire High speed applications bus. Also known as IEEE-1394. Can transfer up to 400Mbps and supports plug and play and is hot swappable. Can support up to 63 devices. Defined speeds of 100, 200 and 300Mbps. Asynchronous and isochronous data transfer allowed, isochronous being the fastest. The cable consists of two twisted pairs which carry the data and control signals and twin power lines. The wire can supply up to 1.5A at anything from 8 to 40V. Can be daisy chained and can have up to 16 on a chain. Can use Firewire nodes to create another three chains from one chain so can have in theory 65,536 nodes in a complete network. ID numbers and resources automatically assigned when device connected and released when device disconnected. A Firewire system can work independently of a PC (unlike USB). Originally introduced in 1995 and developed by Apple. In 2003 a new standard was ratified IEEE1394b which is dubbed Firewire 800 and offers transfer speeds of up to 800Mb/s -Firmware A computer program or software stored permanently in ROM. -Flash An authoring application for web sites. Based on SWF (Shockwave for Flash file format) a web optimised, vector based format. Describes the difference between image frames to enable smooth animations. -Flat file database All of the data is stored in a single table. -FMC Fixed-Mobile Convergence. The basic premise is that people should be able to have a single mobile handset or smart phone to replace a separate desktop and mobile phone. The device should be able to make both VoIP and data calls via the private branch exchanges that route local calls within offices and out onto the PSTN, as well as mobile cellular networks. -FM Synthesis Frequency Modulation Synthesis is a cheap but very reliable means of producing sounds on a PC, but any music does tend to sound artificial. Wavetable synthesis gives much better reproduction. -FOIA Freedom Of Information Act ©IPK30/04/17 -FOIP Fax over IP -FOIRL Fibre Optic Inter Repeater Link - Ethernets standard fibre link. -FOMAUs Fibre MAUs -Fonts True Type fonts (TT) needed by Windows, Arial, Courier New, Symbol, Times New Roman, Wingdings, Comic sans, Impact, Verdana, and Tahoma in all their variations. Dialog boxes, menus etc use bitmap fonts (A icon) need Courier, MS Sans Serif, MS Serif, Small fonts and Symbol. -Forest Domains in Active Directory can be structured into hierarchies called Trees. A forest is a collection of domain trees. Ideally it will cover a whole company. -Format Formats disks. Adding the /S switch tells format to make the disk bootable and install system files. -Formatted Capacity This is the usable size of the hard drive. It is about 15% less than the unformatted capacity. The space is used by the system to map out the usable areas and for managing the data. -Form Factor The physical size of a drive. Common sizes are low profile (LP), half height (HH) and full height (FH). -Forms Gives a user-friendly view of the data held in a database table -FORTRAN Designed by IBM in 1957 - could do complex calculations but could not process data or text. -Foveon X3 Image Sensor Features three separate layers of photodetectors embedded in silicon. The silicon absorbs different wavelengths of light at different depths, so each layer captures a different colour. This is the only type of image sensor to capture red, green and blue light at every pixel location. -FRAM Ferroelectric RAM. Made by Ramtron. A non volatile memory capable of replacing serial EEPROMs but with lower current consumption. Has an unlimited number of read/write cycles. Is faster to program than EEPROMs. -Frame Relay Packet-switched network similar to X25, but with end-to-end error checking and high speed transmission rates. -FRDS Failure Resistant Disk System. Often implemented through RAID system. -FSAA Full Screen Anti Aliasing ©IPK30/04/17 -FSB Front Side Bus. The bus that the processor uses to communicate with the rest of the computer, in particular the main memory. -FSO Free Space Optics. It is capable of gigabit data rates but is restricted to true line of sight links at distances of between 2-3km. Its real deficiency isits poor performance in extreme weather conditions, eg fog, heavy rain etc. -FTDS Failure Tolerant Disk System. Looks to duplicate controllers as well as disks. -FTP Foil Twisted Pair cables -FTP File Transfer Protocol. Used to copy programs often to an ISP. Details on how to do this for Demon on www.demon.net/www/homepages. Common FTP programs include CuteFTP, FTPWolf and BullteproofFTP. FTP - anonymous login - accept 'anonymous' or 'guest' as an ID and usually any word ending with an @ symbol as a password. Considered polite to login with your e-mail address. Archie an FTP search engine invented in 1992. ftp://ftp.demon.co.uk lists of ftp files. To add to the Demon ftp archive ftp://ftp.demon.co.uk/incoming Company ftp site list www.otis.net/companysoft.html FTP has a well defined port number (21), but this is only used for control messages. When a file is downloaded, the FTP server negotiates with the client a higher port number for the transfer to take place on. This means that often a large number of ports have to be left open. Much older than HTTP – first referenced in April 1971 whereas HTTP only appears in May 1996. FTP designed as a two way protocol for moving large files, whereas HTTP designed for pulling lots of small files from a server -Full Height Full height drives are 3.25" tall. -Function Keys F1 F2 F3 F4 F5 F6 F8 F10 Help rename a selected file or folder to send a file or sub folder displays the combo box in Explorer refresh the screen to switch panes in Windows Explorer for special boot menu options like safe mode for menu access GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG -G.711 Speech compression algorithm used with H.323 in VoIP. Requires 64Kbps bandwidth. Needs end to end delay values of 200-300ms and packet loss levels of 2-3% -G.729A Speech compression algorithm used in VoIP. It combines small packet sizes with the voice quality of G711 and delivers a transmission rate of 8Kbps. Requires less that 150 - 200ms for packet loss values of 1-2% ©IPK30/04/17 -GAP Generic Access Profile -GAAP Generally Accepted Accounting Principles - to be replaced with IAS -Gateway A computer system in one network which allows access to another network, by transmitting the data in the protocol of the receiving device. -GC Global Catalogue - part of Active Directory. -GDI Graphical Device Interface. The PC does all of the processing and translating when printing a document from Windows using a laser printer. -GGF -GIF Global Grid Forum - Grid Computing Graphical Interchange Format. Invented by Compuserve. A compression technique, more effective with logos and banners than pictures. Only supports 256 colours. GIF images have the ability to be interlaced so that the image can be downloaded in stages. The GIF image format uses a built-in LZW compression algorithm. This compression algorithm is patented technology and currently owned by Unisys Corporation. In 1995 Unisys decided that commercial vendors, whose products use the GIF LZW compression, must license its use from UNISYS. End users, online services, and non-profit organisations do not pay this royalty. Since it's inception GIF had been a royalty-free format. To avoid this royalty, vendors have developed an alternative to GIF that supports transparency and interlacing called PNG ("ping"), the Portable Network Graphic. GIF87a was released in 1987. GI87a allowed for the following features:LZW compressed images multiple images encoded within a single files positioning of the images on a logical screen area interlacing. So it was possible to do simple animation with GIFs by encoding multiple images, "frames", in a single file. GIF89a is an extension of the 87a spec. GIF89a added: how many 100ths of a second to wait before displaying the next frame wait for user input specify transparent collar include unprintable comments display lines of text indicate how the frame should be removed after it has been displayed application-specific extensions encoded inside the file Most browsers support single image GIF87a and will recognise the transparency flag of GIF89a and nothing else. All transparent GIFs are GIF89a format. GIF89a is still a 256-colour (maximum) format. GIF allows for any number of colour between 2 and 256. The fewer colours the less data and the smaller the graphic files. If your GIF only uses 4 colours, you can reduce the palette to only 2 bits (4 colour) and decrease the file size by upwards of 75% The Structure of a GIF89a file. GIFs are composed of Blocks and Extensions. Blocks can be classified into three groups: Control Graphic-Rendering Special Purpose ©IPK30/04/17 Control blocks, such as the Header, the Logical Screen Descriptor, the Graphic Control Extension and the Trailer, control how the graphic data is handled. Graphic-Rendering blocks such as the Image Descriptor and the Plain Text Extension contain data used to render a graphic. Special Purpose blocks such as the Comment Extension and the Application Extension are not used by GIF decoders at all. The Logical Screen Descriptor and the Global Colour Table affect all the images in a single file. Each Control block will only affect a single Image block that immediately follows it. GIF89a File Structure. GIF89a HEADER LOGICAL SCREEN DESCRIPTOR BLOCK may include an optional GLOBAL COLOUR TABLE (99.5% of the time this will be present) optional NETSCAPE APPLICATION EXTENSION BLOCK a stream of graphics (each graphic being composed of the following) an optional GRAPHIC CONTROL BLOCK (one preceding each IMAGE) a single IMAGE DESCRIPTOR or PLAIN TEXT BLOCK which can include an optional LOCAL COLOUR TABLE for an image and the actual IMAGE or TEXT data table GIF TRAILER ends the series of images COMMENT BLOCKS may appear anywhere as they are ignored. (Do NOT place them before the Netscape Looping Extension!!) BLOCK DEFINITIONS: HEADER The HEADER block is a small 6-byte (6-character) block. It is the first block in every file and contains the GIF version of the file (i.e. either GIF87a or GIF89a). GIF image decoders use this information to determine the version of the file. LOGICAL SCREEN DESCRIPTOR The LOGICAL SCREEN DESCRIPTOR is always the second block in a file. It defines an area of pixels which you can think of as a screen (like a projector screen). The dimensions of this area define the size of your GIF on screen. This information determines how much space is reserved onscreen in your browser to display the image. If your logical screen is larger than your image, you will have space around the image when displayed. The logical screen area should be large enough to display all of your individual frames in it. If an image in the GIF file is larger than the logical screen or, by its positioning, extends beyond the screen, the portion that is off-screen will not be displayed. The Logical Screen Block also chooses one of the colours in the Global Colour Table to be the Background colour of the screen. This colour selection is ignored by Netscape Navigator. If a GIF's background area shows through, Navigator displays the colour set in the BGCOLOR of the page's body or, if none is specified, the background colour set in the menus under OPTIONS/GENERAL PREFERENCES/COLORS. Now, of course, the question arises; how do I get it to be transparent? Well, this SHOULDN'T work, but it does. Apparently, if Netscape's decoder finds a Control block (it must be first, before any images) with Transparency turned on (any colour) the background of the GIF will be transparent. This will allows background GIFs to fill in the logical screen background. A GIF file contains a global palette of common colours for all the images in its file to work from. (NOTE: It is technically possible for a GIF NOT to have a global palette, but this would be extremely rare.) This palette can have 2, 4, 8, 16, 32, 64, 128 , or 256 defined colours. Palettes are very important. Every colour displayed in your GIF must come from a palette. The fewer colours used, the easier it will be for systems to display your images. The global palette is applied to all images in a GIF file. If an individual images differs greatly from that global palette, it may have a local palette that affects its colour ONLY. However, no image can ever reference more than one palette, so 256 colours per image is the max. Having a bunch of local palettes with wildly varied ©IPK30/04/17 colours can sometimes cause colour shifts in your display. (It also probably indicates a gaudy mix of colours). The Logical Screen Header can also contain the aspect ratio of the image. This can sometimes account for GIFs appearing stretched out or scrunched. Netscape Navigator has an Application Extension Block that tells Navigator to loop the entire GIF file. The Netscape block MUST APPEAR IMMEDIATELY AFTER THE GLOBAL COLOUR TABLE OF THE LOGICAL SCREEN DESCRIPTOR. Only Navigator 2.0 or better will recognise this Extension block. The block is 19 bytes long composed of: (note: hexadecimal equivalent supplied for programmers) byte byte byte 1 2 3 : 33 (hex 0x21) GIF Extension code : 255 (hex 0xFF) Application Extension Label : 11 (hex (0x0B) Length of Application Block (eleven bytes of data to follow) bytes 4 to 11 : "NETSCAPE" bytes 12 to 14 : "2.0" byte 15 : 3 (hex 0x03) Length of Data Sub-Block (three bytes of data to follow) byte 16 : 1 (hex 0x01) bytes 17 to 18 : 0 to 65535, an unsigned integer in lo-hi byte format. This indicate the number of iterations the loop should be executed. bytes 19 : 0 (hex 0x00) a Data Sub-block Terminator. The iteration count is ignored and the loop is infinite (an iteration count of zero indicates infinite). I strongly suggest you code the count to be accurate, so that when iterations begin working your GIF will not need to be modified. Technically that is all that needs to be done with this block. CONTROL BLOCKS A CONTROL BLOCK controls certain optional aspects of how an image is displayed. A Control block only affect the image immediately following it. For this reason, you should never include any block between a control block and the next image descriptor block. This Graphic Control Extension defines: if this image has a local palette of its own if one of the colours in this image is transparent if a user input is requested before proceeding if a timed delay in 1/100ths of a second should be used before displaying THIS image. what should be done with the image after it has been displayed (removal controls) You should avoid using a local palette as it increases the likelihood of a confused video display. If a local palette doesn't exist, the global one is used. One of these colour is designated as transparent in the control block. User input and timing work together. When an image is described, it is immediately rendered on screen. Then, if a timed delay is set, it will wait for x/100ths of a second before removal and proceeding onto the next image. If a User Input is specified, the image waits until the user strikes a key, clicks a mouse or whatever. What is considered user input is determined by the program displaying the GIF. If both options are elected, the image remains until the delay expires or a user input occurs, whichever comes first. Just before preceding to the next image, the removal options are performed. You may remove the image by: nothing: perform no action leave as is: leave the image on screen, should be same as nothing in most cases previous image: replace it with what was there before; this is difficult to implement and is the most powerful choice. background: replace with the logical screen background colour. (note: If Navigator detected transparency, this will be replaced by the HTML specified background) ©IPK30/04/17 IMAGE BLOCK An IMAGE BLOCK contain (data) an actual image. This image can be any size and have a palette of any size. You can have a mix of 16-colour, 2-colour, 256 colour, etc images in a single GIF. In addition to the actual image table data you have the following: the picture's size in pixels the position of the image on the logical screen whether it is interlaced an optional local palette for this image The image's size in pixels cannot be modified. It is determined by the data of the image. Changing this would cause data corruption. The top and left position of the images are within the defined logical screen. With this a small bitmap of an object could be placed anywhere within the screen area, rather than create an entire image with the object positioned within it. Interlacing is a way of saving and displaying the image data. For interlacing to occur, the image must be set to save interlaced. Interlacing is not turned by the browser. It may be ignored by the browser. Interlacing saves alternate rows, producing a venetian blind or blocky-focusing effect, depending upon how the browser handles interlacing. Interlacing stores the rows of the image in the following order: Pass Pass Pass Pass 1 2 3 4 : : : : Every Every Every Every 8th. 8th. 4th. 2nd. row, row, row, row, starting starting starting starting with with with with row row row row 0. 4. 2. 1. COMMENT BLOCK You can include comments in your GIF. These can be markers for long animation sequences or statements of ownership. PLAIN TEXT BLOCKS In addition to images you can also render text on screen with a GIF. Unfortunately many programs don't recognise the text. TRAILER The Trailer is simple. It indicates the end of the GIF file. It is unmodifiable and cannot be accessed in anyway. The block types and features contained in the animated GIF: HEADER Dimensions (x,y) Aspect ratio (0=1:1) Global palette: Bit-depth (1-8) "Background colour" index (0-255) Sorted by frequency? (y/n) Colour table LOOP Repetitions (0-65535) CONTROL One per image Transparent color index (0-255) Delay (0-65535) User input? (y/n) Disposal method (0-3) IMAGE One or more Dimensions (x,y) Position (x,y) Interlaced? (y/n) Image description ©IPK30/04/17 Local palette? (y/n) If present: Bit-depth (1-8) Sorted by frequency? (y/n) Color table -Google Search engine - www.google.com. Searches for phrases - put into quote. OR searches - include upper case OR + searches - words like and are ignored. If the word is essential include a + directly before the word and a space after the word. - searches - used when a word can have two meanings, e.g. bass - fish or music. Just to find the music pages search for "bass -fish " -Google site operators Can be used to search out whole domains for specific words. eg the query "site:edu test answers" would return a list of every .edu domain that possessed the words "test" and "answers". The site operator can also be used to map the contents of a target web server. The query "site:www.sc magazine.com scmagazine will return a list of every web page held by the scmagazine.com web server bearing the words "sc magazine", which is all of them. The operator "intitle:index.of parent directory," allows the directory listing and structure to be obtained from the Google cached data. The operator "filetype: " allows a particular type of document to be searched for specific words. eg "filetype:pdf security" The operator "link: " is used to search for sites with links to a specific site The operator "cache: "is used to find all cached pages of a specific site The operator "allintitle: " allows whole sentences to be identified in web pages. The operator "inurl: " allows web pages to be located with specific words or sentences in their URLs. The scariest features of the Google engine is its ability to locate "CGI" or "web" scanning directories containing sample software code or vulnerable files. Using either the "index.of" or "inurl" operators, and then attaching the desired target directory or file namevulnerable targetswill be located from the Google data cache. eg "inurl:admin filetype xls password," produces exactly what you think it would. For more information enter "Google Hacking" intoGoogle and read the results -Google Web Toolkit (GWT) An Ajax development framework for Java programmers. They write their program front-ends in Java and the GWT compiler converts it to browsercompliant Javascript and HTML -GOP Group of pictures – method of compression used with MPEG encoding. -GPF General Protection fault. Windows way of warning that a program has tried to access a portion of RAM that is protected from unauthorised access. In practice it means that the program has crashed and the computer needs rebooting. GPFs in user.exe often mean problems with drivers for sound cards or input output devices like the keyboard or mouse, while GPFs in gdi.exe often relate to video driver problems. One possible fix is to edit the config.sys file so that it contains a line 'FILES=100'. -GPRS General Packet Radio Service. Allows packet based communication to take place over a GSM phone network. Often referred to as 2.5G. Data rates quoted as 56Kbps to 114Kbps though it is usual to achieve speeds of around 40Kbps. Provides a cheaper form of ©IPK30/04/17 communication as channels are shared between users and only used during transmission. To connect to a GPRS network a user needs the (APN) Access Point Name of the network. -GPU Graphics processing unit. -GRE Generic Routing Encapsulation. -Grid computing Allows spare processing power of multiple computers on a distributed network to be applied to a common goal. Method of using many computers around the world for large projects as in the SETI project. -Group Used on Windows NT. A predefined collection of access permissions and rights assigned to a collection of users. -GSI Government Secure Intranet -GSM Global System for Mobile phones. 900MHz or 1800MHz -GUI Graphical User Interface. HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH -H.323 One of the major protocols for VoIP. A standard approved by the ITU in 1996 to promote compatibility in videoconference transmissions over IP networks. -Half Height Half height drives are 1.67" tall. -Half toning. This process involves laying down larger or smaller dots to create a more realistic image -Handshaking Exchange of predetermined signals between two devices establishing a connection. Part of a communications protocol. -Hard Drives Typical rotation speeds of 5400, 7200 and 10000rpm. These improved drastically with the replacement of the stepper motor with a voice-coil motor. In older hard disk drives , a stepper motor moved the read/write head along the disk surface in a series of discrete steps. The new voice-coil motors, however, aren’t limited in their movement by a series of predetermined increments. Instead, the voicecoil motor spins smoothly, without the slightest interruption needed to account for the steps. Use of the voice-coil motor also has improved the average seek time. Average seek time, usually given in milliseconds (ms), measures the amount of time required to move a hard disk’s read/write head to a particular location. The older stepper motors accounted for seek times of 120ms. But because the voice-coil motor simply reacts to the ‘voice’ of the magnetic data, the read/write head may move directly to the areas of stored data. The voice-coil motor allows the read/write head the freedom a computer to move towards any spot on the disk where data is ‘speaking’. The average seek time is now 8 – 17ms. Recent jump in storage density has two main causes: (a) the use of giant magneto-resistive (GMR) read-write heads which increase the sensitivity by a factor of four. These are being combined with new thin film low noise cobalt alloy storage media ©IPK30/04/17 on the platter which provides an ultra smooth surface and allows the GMR head to fly 15nm above the platter. (b) spindle speeds have increased to 10,000rpm giving data transfer rates of 325MB/s Hard Disk Drive Size. Initially restricted to 528MB. This was due to the ATA standard and the BIOS interrupt (int 13H) that received information about the geometry of the disk, This meant that disks could have only a maximum of 1024 cylinders. The ATA standard used 16 bits for the cylinder number, four for the head and eight for the sector. However int 13H used 10 bits for the cylinder, eight for the head and six for the sector. Since both standards were being used, the smallest bit depth from each had to be used, meaning a total of 20 bits were used for the geometry. Despite the fact that Ultra ATA can support up to 137GB and int 13H up to 8.24GB, the combination of the two meant a 528MB limit. The solution was LBA (Logical Block Addressing) BIOS translation, which gives each sector on the disk a unique number and addresses them by this rather than the cylinder, head, sector method. Overcoming the limitation of the interrupt meant extending the bit depth to 64 bits, which gives a maximum of 9.4 x 1018 bytes. This left the 137GB limit of 28 bit LBA as the next major barrier and the possibility of 48-bit LBA would give a limit of 144 x 1015 bytes. -Hardware Abstraction Layer. An isolated memory space that programmers can use to write device-independent applications -Hash Hashes are used to make digital signatures of digital data. The datasets can be of variable length and even the smallest change in the data should result in a different hash value. MD5 is a common function to produce hashes -Hayes command set A set of instructions for controlling basic modem functions such as dialling, and hanging up, devised by the modem manufacturer Hayes -HCA Host channel adapter, an adapter that connects a server to an InfiniBand link. -HDCD High Definition Compatible Digital. The format is backwards compatible with standard CD players. It works by using the least significant bit of CD's 16 bits to encode additional information which results in a 20-bit per channel encoding scheme. Need a separate HDCD decoder -HDLC High level Data Link Control -HDMI High Definition Multimedia Interface. -HDTV High Definition Digital Television. Two resolutions 1280x720 and 1920x1080. Both are 16:9 widescreen ratios. -HDV High Definition Video. cf DV. Two resolutions 1440x1080 and 1280x720. Usually referred to by their horizontal resolutions and the frame rate. => 1080/50i and 720/25p or 720/50p where i stands for interlaced fields and p for progressive scan. Usually employs MPEG2 compression -HDX Half Duplex. Transmission in either direction but not simultaneously. ©IPK30/04/17 -Helical scan Originally used for video recording. The first widely used format for back up tapes was DDS, the data version of Digital audio Tape. In a helical scan tape drive, the media is drawn out of the cartridge and passes over a drum that rotates at high speed. The drum contains both read and write heads and is set at an angle, with data written in offset stripes. This allows more data to be stored on the tape in a given area. The main disadvantage is the wear of the tape against the rotating drum -Heuristics An antivirus technology that looks for indications of virus activity such as suspicious codes or unanticipated changes in files. -Hiperlan2 a standard similar to IEEE802.11a. An European wireless network standard aimed at two different frequency bands - 5.15-5.25GHz and 17.1 - 17.3GHz. Power output is restricted to 1W in the lower band and 100W in the higher. It is similar to 802.11a in the lower band but less well developed. -HIPPI High Performance Parallel Interface. See Fibre Channel. It is a standard for connecting two devices together over short distances. The standard version transfers 32-bits at transfer rates of 800Mbps. Wide HIPPI doubles the transfer rate to 1.6Gbps by transferring 64-bits in parallel. -HIPS Host Intrusion Prevention System -History 1981 12th August IBM launched the Personal Computer, running DOS. The cheapest was $1565 1982 Compaq Computers introduced the Compaq Portable PC, an IBM clone 1983 Lotus ships the killer PC application - Lotus 1-2-3 spreadsheet, the most complex PC application of its time. 1985 Intel produces the 80386 microprocessor 1986 Amstrad launches the PC1512, which cost £399 1987 IBM developed OS/2, the first PC operating system that allowed people to use a mouse. 1988 Microsoft becomes the number one software maker. 1989 Tim Berners-Lee and his team at CERN develop the web. 1991 IBM partners with Apple and Motorola after Microsoft falls out with IBM over its big enterprise OS project, Windows NT 1993 Linus Torvalds develops Linux. 1994 Marc Andressen and Jim Clark release the web browser Netscape 1995 Microsoft launches Windows 95 1997 Compaq moves into high-end computing and buys Tandem for $3bn 1999 Melissa, the world's first macro virus wreaks havoc. 2001 Intel releases the first 64-bit processor, Itanium 2003 AMD releases an entry-level 64-bit processor 2004 IBM sells PC business to Chinese IT supplier Lenovo -Honeypot A server with an unpublished IP address. Connected to the Internet. Any access of the server is likely to be from unauthorised activity. Tools running on the honeypot inspect the incoming TCP/IP connections and can automatically produce signature files that would allow a firewall to filter out any such packets sent to published servers. -Hot Plug Means that a drive can be connected or disconnected whilst there is power going to it. Mainly used in SCSI based RAID arrays. ©IPK30/04/17 -HPF High Performance Fortran. A superset of Fortran 90 and often used on parallel programming clusters -HSCSD High Speed Circuit Switched Data. Gives 28.8Kbps on a GSM phone. GPRS the next step forward for higher speed. HSDPA High-Speed Downlink Packet Access. Used on 3G phone network. Theoretical peak data transfer rates up to 14.4Mb/s in downlink and up to 5.8Mb/s in the uplink. HSDPA is spectrally efficient, so there can be more users per cell. Also known as 3.5G. It runs over a 5MHz bandwidth on W-CDMA -HSL Hue, Saturation, Luminosity. Hue is a colour defined by a number between 0 and 360 - as in a colour wheel. RED BLUE GREEN The primary colours are spaced at 120º. Saturation is like the Contrast on a monitor. Luminosity is like the Brightness on a monitor. -HSLAN High Speed Local Area Network -HTML HyperText Mark-up Language. It is effectively a programming language designed for telling the page what images go where , what links to what etc. It began life in 1995 as the W3C's answer to incompatibility problems between different suppliers' browsers. It is based on SGML (Standard Generalised Markup Language) but is much simpler. Now progressed to XHTML. -HTTP Hyper Text Transfer Protocol. This is the protocol used by the Internet to transfer HTML code to your browser for interpretation. Specifies that headers are separated from the actual content by two line feeds. -HTTPS Hyper Text Transfer Protocol Secure. This is a secure encrypted version of HTTP used on e-commerce sites. A closed padlock icon on the browser sometimes indicates it. Usually uses SSL -Hub The centre of a star topology network or cabling system. When it receives a signal it refreshes it and strengthens it before passing it on. -Human Rights Act Individuals have a right to respect for their private life and correspondence. Came into effect in the UK on October 2000. -Hyperlan 2 band 5GHz radio band ©IPK30/04/17 -Hypertext A method of presenting information so users can jump around a document by clicking on a highlighted word or icon. -Hyper-Threading Intel. Makes more use efficient use of processor resources by running more of them in parallel. Hyper Threading splits a Pentium 4 or Xeon processor into two logical CPUs, so that if two sets of instructions use different registers they can be processed at the same time. However, the two threads need to be complementary - so that they don't execute the same instruction at the same time. -HyperTransport runs at 51.2Gbps. Links the IGP (Integrated Graphics Processor and the MCP (Media Communications Processor). It is a royalty free and open industry standard for the point to point link for ICs. The technology provides a universal connection, designed to reduce the number of buses within a system and provide a high performance link for embedded applications. It also aims to enable highly scalable multiprocessing systems. The interface delivers 16Gbps bus bandwidth. IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII -IAA Intel Application Accelerator - Improves IDE Disk Drive access for Intel chip sets. http://downloadfinder2.intel.com/scripts-df/product_filter.asp?productid=816 -IADs Integrated Access Devices -IANA Internet Assigned Numbers Authority. The following IP addresses are reserved for private local networks. 10.0.0.0 - 10.255.255.255 172.16.0.0 - 172.31.255.255 192.168.0.0 - 192.168.255.255 162.254.0.0 169.254.255.255 -IAS Internet Authentication Service. W2k VPN -IAS International Financial Reporting Standards. To replace GAAP -IC sizes Athalon and Pentium III, the components are 0.18m and the pathways joining the components are only about 100 molecules wide. -ICANN The Internet Corporation for Assigned Names and Numbers. -ICF Internet Connection Firewall -ICMP Internet Control Message Protocol. Runs in the Network layer. It reports unexpected events and is encapsulated as an IP packet. The allowed messages include: Destination unreachable Warns that the packet could not be delivered. Echo request Asks a machine if it is alive. Echo reply Responds to an echo request. Parameter problem A field in the header was invalid. ©IPK30/04/17 Source quench Tells a fast transmitter to back off as it is flooding the receiver. Timestamp request Same as echo request but asks for a timestamp as well. Timestamp respond Reply to timestamp request. A practical use of ICMP is PING, which sends an echo request to make sure that a remote computer is up and running. -IDA Intelligent Document Architecture -IDE Integrated Drive Electronics. The most popular type of hard drive system. The controller electronics are included inside the device. The electronic intelligence for operating the disk is inside the hard disk itself. Limitations; disks smaller than 528MB, only two hard disks in one computer. Max transfer rate about 4MB/s. -IDE Integrated Development Environment. Used by programmers for enhancing productivity when programming. -IDS Intrusion Detection System -iDTV Interactive Digital Television -IE See Internet Explorer -IEEE Institute of Electrical and Electronic Engineers. The US based society that uses its own standards and is a member of ANSI and ISO. -IEEE 1394 A peer to peer communications system. Allows 63 peripherals on the same connection. The standard allows for up to 1023 busses to be bridged together. 1394b specification provides connection speeds of 800Mb/s -IEEE802.1P An Ieee standard for providing quality of service within a LAN -IEEE802.11 The initial draft of the WLan standard. It provides 1 or 2Mbps transmission using the 2.4GHz band. -IEEE802.11a Wireless standard - up to 54Mbps using the 5GHz band. Ratified after 802.11b. Intended to have a range of over 200ft in an office environment. -IEEE 802.11b Wireless standard - up to 11Mbps over a radius of 100m using the 2.4GHz band. First ratified in 1999. Uses 24 bytes of pre-amble in the physical layer. PLCP Physical Layer Convergence Protocol. Also known as WiFi. 2.4GHz to 2.4835GHz. This frequency band is also used by Bluetooth, microwave ovens, ISM equipment. 13 different channels (numbered 1 to 13). Cards can only listen to one channel at a time. 83MHz wide - divided into 11 x 22MHz wide channels all of which overlap with each other apart from channels 1, 6 and 11. -IEEE 802.11e example. Defines quality of service for WLANs, to support voice over IP, for ©IPK30/04/17 -IEEE 802.11g Successor to 802.11b. Achieved by the use of OFDM. In theory 54Mbps possible at 2.4GHz. -IEEE 802.11h This is the extension of 802.11a which introduces the power control and frequency features required by European legislation. The frequency range 5.25 - 5.35GHz is used by a number of military and satellite radar networks. So in Europe can only access the first four frequencies within Band A (5.150 - 5.350GHz). This standard requires equipment to have TPC (Transmit Power Control), which limits the transmit power to the absolute minimum and DFS (Dynamic Frequency Selection), which allows wireless equipment to shift frequency if a radar signal is detected. MaxEIRP is 60mW for equipment without TCP and 120mW with TCP. -IEEE 802.11i Wireless security standard of which WPA is a subset. A secure replacement for WEP -IEEE 802.11j The Japanese equivalent of 802.11h -IEEE 802.11n A proposed spec to double the speed of 802.11a/g WLAN. Equipment expected in 2006. Speeds of 150Mb/s to 350Mb/s - rising to 600Mb/s -IEEE 802.11n-MIMO Multiple Input Multiple Output. A number of aerials transmit many unique data streams in the same frequency channel -IEEE 802.15 A standard for personal area networks, based on Bluetooth -IEEE 802.16 Specification for fixed-wireless broadband. -IEEE 802.16a Allows the use of the 2GHz to 11GHz range for WLANs. Also called WiMax, can transfer up to 70Mb/s over as much as 30 miles -IEEE 802.1x Authentication scheme based on EAP (Extensible Authentication Protocol) -IEEE 802.20 Proposal for 1Mb/s wireless metropolitan area networks -IEEE 802.3 A physical layer standard that uses the CSMA/CD access method on a bus topology LAN. Defines 10Mb/s Ethernet. -IEEE 802.3u Standard which defines 100Base-T or fast Ethernet. Finalised 1997 -IEEE-1394 High speed applications bus. Also known as Firewire. -IEEE P802.3ae 10 Gb/s Ethernet standard. Also known as 10GE -IEMSI Interactive Electronic Mail Standard Identification. Universal e-mail standard so that it can be used cross platform ©IPK30/04/17 -IETF Internet Engineering Task Force. Working to improve the capacity, performance of SANs and the internet in general. Defines standard internet operating protocols such as TCP/IP -iFCP Internet Fibre Channel Protocol A SAN interconnect protocol. -IFRAMES Floating pop-up frames. -IGP Integrated Graphics Processor. Integrated Graphics Port. -IIS Microsoft Internet Information Server - web server for Windows. -IL Intermediate Language. ILM Information Lifecycle Management -IM Instant Messaging. -IMS IP Multimedia Subsystems. Developed by 3GPP to provide the telecom industry with a modular, standards-based IP/SIP service delivery infrastructure. -IMAP4 Internet Message Access Protocol. A method of sending email across the Internet. Originally developed in 1986 at Stanford University - similar in operation to POP3 but offers better interaction between e-mail clients and servers. -Indigo The Windows Communication subsystem in Windows Vista. -InfiniBand the next generation of I/O architecture and is set to replace PCI. It offers throughput of up to 2.5Gbps and supports 64000 addressable devices. Uses a serial bus in a similar way to a network. -Inkjet printer Squirts minute drops of ink from tiny nozzels directly onto the paper. Based upon thermal print heads, though the Epson stylus range use a piezoelectric mechanism to squirt the ink drops. the nozzels are around 1/500th of an inch. The ink is heated to around 1000ºC in the nozzle for 3 millionths of a second. The intense heat causes the ink to boil and form a bubble (hence the name BubbleJet used by Canon.). As the bubble bursts, a tiny quantity of ink is forced through the nozzle and onto the paper. Tend to be slow and expensive to run. -Internet Deleting visits. Navigator's Cache folder is inside the Navigator folder. Internet Explorer's Cache folder is inside the Windows Temporary Internet Files folder Navigator's cookie folder is called cookies.txt. Find using Windows find. Internet Explorer keeps its cookies in a folder called cookies inside the windows folder. History files. Netscape Navigator in the netscape.hst file. Internet Explorer look in the Windows\History folder. Registry: Use the Registry Editor window, select Edit, Find and then enter URL History. Select and delete the URLs but not the default listing ©IPK30/04/17 Navigator users should also select and delete the URLs they find in hkey_local_machine/software/netscape/netscapenavigator, opening the version number folder if necessary. Internet explorer users will find additional URLs in hkey_users/software/microsoft/internetexplorer/typedurls. Deleting all traces of Web activity. Run the batch file after closing the browser. For Netscape Navigator: echo y>c:\windows\tempor~1\y.txt del c:\progra~1\netscape\naviga~1\cache\*.*<c:\windows\tempor~1\y.txt del c:\progra~1\netscape\naviga~1\cookies.txt del c:\progra~1\netscape\naviga~1\netscape.hst del c\windows\cookies\*.*<c:\windows\tempor~1\y.txt del c:\windows\history\*.*<c:\windows\tempor~1\y.txt del c:\windows\tempor~1\*.*<c:\windows\tempor~1\y.txt For Internet Explorer echo y>c:\windows\tempor~1\y.txt del c:\windows\cookies\*.*<c:\windows\tempor~1\y.txt del c:\windows\history\*.*<c:\windows\tempor~1\y.txt del c:\windows\tempor~1\*.*<c:\windows\tempor~1\y.txt Or use NSClean Privacy Software from www.wizvax.net/kevinmca for Netscape Navigator or IEClean for Internet Explorer from the same place. Address books with file suffix *.pab or *.wab -Internet2 Based on 10Gb/s Ethernet. It is a consortium led by 207 universities working in partnership with industry and government to develop and deploy advanced network applications and technologies. One of the projects to come out of Internet2 is Abilene, part of the Internet2 backbone network and a system that enables US-wide testing of applications such as uncompressed high-definition TV-quality video; remote control of scientific instruments such as mountaintop telescopes and electron microscopes; collaboration using immersive virtual reality; and grid computing. -Internet Country codes AU BD BE BR CA CH CL CN CZ DK EG ES FI FR DE GR HK IN Australia Bangladesh Belgium Brazil Canada Switzerland Chile China Czech Republic Denmark Egypt Spain Finland France Germany Greece HongKong India ©IPK30/04/17 IE JP MY MX NL NZ NO PK PL RU SA SE TR TW UK US ZA Ireland Japan Malaysia Mexico Netherlands New Zealand Norway Pakistan Poland Russia Saudia Arabia Sweden Turkey Taiwan United Kingdom United States South Africa -Internet Explorer Kiosk mode iexplore -k Allows internet explorer to run full screen. IE6 - need to install Quicktime - www.apple.com/quicktime/download/qtcheck IE6 - need to install Java Virtual Machine - www.microsoft.com/java IE6 - Disable Error reporting to MS. On non XP machines HKEY_LOCAL_MACHINE\Software\Microsoft\Internet Explorer\Main. Create DWORD value called IEWATSONENABLED and set value to 0. IE6 - printing. Text scaling with CTRL and mouse scroll wheel. Headers and footers - use printer control codes Window title &w URL in full &u Date (short) &d Date (full) &D Time &t Time (24hr) &T Current page number &p Total page count &P Right align &b<text> Centre align &b<text>&b Security settings. Adding to Trusted and Restricted sites *.domain.com eg *.ikes.freeserve.co.uk -InterNIC Internet Network Information Centre. -Interpreter Translates a high level language to machine code one statement at a time and executes it before translating the next statement. -Interval Arithmetic Notes the boundary values of uncertain parameters and removes the levels of inaccuracy -Intranet information etc A private internal network, based on TCP/IP, for providing ©IPK30/04/17 -Invalid page Fault Caused when a page of data or program code in the swap file cannot be loaded into the main memory. -IP Internet Protocol. Usually a set of four numbers eg 193.195.224.1. Everything that is connected to the Internet has its own unique number. LANs may have just one IP address to connect to the outside world. ISPs do not have enough IP addresses to go round and so will allocate dynamic IP addresses, which change each time you log on. IP protocol corresponds to the network layer in the seven-layer OSI model. The IP datagram consists of a header that contains addressing and general options and a data part. The header has a 20 byte fixed part and a variable length options part. See diagram below. IP header 32 bits version IHL type of service identification time to live total length DF MF protocol fragment offset header checksum source address destination address options (0 or more words) Version IHL Version of IP being used IP v4 or IP v6 Contains the length of the header. The minimum value is 5 when there are no options and a max value of 15, which restricts the options field to 40 bytes and the header to 60 bytes. Type of service Defines the level of service that a packet gets, eg streaming video needs fast delivery and file transfer needs reliability. This field contains a three bit precedence field, three flags (D, T and R) and two unused bits. precedence takes a value from 0 to 7 which specifies the priority of the datagram. The flags are used to emphasise what the datagram finds important, delay, throughput and reliability. In practice most routers ignore this field. Total length This 16 bit field specifies exactly how long the datagram is including the header. The maximum length of the packet is therefore 65,535 bytes. Identification Tells the receiving computer which datagtram a fragment belongs to. All fragments in a datagram have the same identification value. The next bit is unused. DF A one bit field that means 'don't fragment'. It tells routers that the receiving computer cannot reassemble fragments. However all machines are required to accept fragments of 576 bytes or less. MF A one bit field that means 'more fragments' and is used to instruct the receiving machine that more fragments are on the way. All fragments, except the last, are marked with this field. If the field has no entry, then it means that this fragment is the last. Fragment offset A 13 bit field defines exactly where in the datagram the fragment belongs. It helps the destination machine reassemble the datagram in the correct order. ©IPK30/04/17 All fragments, except the last, have to be a multiple of eight bytes long. The 13 bits give a maximum of 8192 fragments, which gives a maximum datagram length of 65536 bytes (8192 x 8), which is one byte more than the total length field. Time to live (TTL) An eight bit field that determines the time in seconds that a packet can stay on the network. This gives a maximum of 255 seconds. Prevents a datagram bouncing around forever. In practice the TTL field is decreased by one every time it hakes a hop. When the TTL hits 0, the datagram is removed from the network and a warning sent to the source host. Protocol Defines which protocol to use for the transport process. Most common are TCP and UDP. Header Checksum This field carries a checksum for the header alone. Used to ensure that it does not get corrupted. It has to be updated at each hop as some fields, e.g. TTL, will change each time. Source Address 32 bit field giving the origin of the datagram. Destination address 32 bit field giving the destination of the datagram. Options Currently only five options are defined, but not all routers support them. Security How secret is the datagram? Strict source routing Defines the route to take. Loose source routing Lists routers that can't be missed Record route Traces the route by making routers append their IP addresses. Timestamp Each router appends its address and timestamp. Typically the 40 byte length of this field is not long enough for the record route and timestamp. The options length limit was set in the early days of Arpnet when no datagram ever passed through more than nine hops. -IP Addresses A 32 bit binary number often quoted as 4 eight bit numbers. This gives each quarter of the address a maximum value of 255. The full address is actually a combination of two addresses: host and network. The network address is used by routers to get a datagram to the destination network e.g. bbc.co.uk. Once the datagram reaches the network, the network address is ignored and the datagram routed to the correct host. Networks are classed by A, B and C domains. There are also class D and E domains but they are for multicast use. IP address ranges 32 bits Class A 0 B C network 10 110 host address range 1.0.0.0 to 127.255.255.255 host network 128.0.0.0 to 191.255.255.255 host network host 192.0.0.0 to 235.255.255.255 The diagram above shows how the header on the IP address differentiates each class of network and the range of IP addresses available to the host. Each class defines the number of bits to use for the network and host address respectively. A larger network address reduces the number of hosts on the network. The table below shows how many networks can exist in each class and the number of hosts that each network can hold. ©IPK30/04/17 Class A B C Number of networks seven bit address: 126 14 bit address: 16384 21 bit address: 2,097,152 Number of hosts per network 24 bit address: 16,777,216 16 bit address: 65536 eight bit address: 256 In addition to this there are several reserved addresses. 0.0.0.0 is used by hosts while they are booting, but not used after that. IP addresses that have a network address of 0 refer to the current network. This allows hosts to transmit to local machines without knowing the network they are on. However they need to know the class of the network so that they can insert the correct number of 0s. Broadcasts are handled by filling the address with 1s, which sends packets to all machines on the local network. Broadcasts can be sent to remote sites by filling out a proper network address, but putting all 1s as the host address. All addresses in the 127.X.X.X space are reserved for loop back testing. Packets sent to that address are not sent out but are processed locally. This is typically used for debugging and usually with the address 127.0.0.1. 192.168.0.x This range of IPs is allocated for use by private networks that are not directly accessible via the internet. Use subnetmask of 255.255.255.0 -IPI Intelligent Parallel Interface. See Fibre Channel. A high bandwidth interface between a computer and a storage device. Operates with transfer speeds of 25MBps and supports RAID. -IPP Internet Print Protocols. -IPS Intrusion Prevention System. Two types - Host IPS (HIPS) and Network IPS (NIPS) -IPSec Internet Protocol Security -IPv4 Gives a 32 bit number -IPv6 Gives a 128 bit number compared to the 32 bit number of IPv4 giving approximately 340 billion, billion, billion, billion, billion, billion, billion unique addresses. Numbers written in hex and separated by colons not dots. ABCD:0000:0000:0000:00FE:22DC:FFDE:CAD2 Leading zeros can be omitted. ABCD:0:0:0:FE:22DC:FFDE:CAD2 Strings of consecutive zeros can be replaced by two colons ABCD::FE:22DC:FFDE:CAD2 -IPVPN IP-based Virtual Private Network. Either delivered over a private IPbased network or the public internet -IPX/SPX Internet Packet Exchange / Sequence Packed protocol. Compatible with both Windows and Novell Netware. Not suitable for the Internet or even wide area networking in most cases, IPX is a connectionless protocol best applied to 'bursty' LANs where data traffic flows in fits and starts rather than continuous streams. The other half of the partnership - SPX- is connection orientated. It is used to establish permanent or long term connections between specific network nodes which copes with a large and regular amount of traffic. -IRC Internet Relay Chat ©IPK30/04/17 -IRM Information Rights Management -IRQ Interrupt ReQuest. A signal that interrupts the processor to gain its attention. PCs support up to 15 separate IRQs. Every PC has 16 IRQ lines. PCI bus allows more than one device use a single IRQ. MSD in Win3.1 shows IRQs. Win95; right click My Computer, choose Properties, click the Device Manager tab and double click the Computer Icon for a complete list. Note: IRQ2 and IRQ9 are actually one IRQ. IRQ5 is the most popular assignment for expansion cards, eg SoundBlaster. Every PCI card shares the single IRQ that the system assigns to the PCI bus, often IRQ11. -ISA Industry Standard Architecture. The original PC setup which allows extras to be added to a system by inserting plug in adapter cards into slots on a mother board. These are 16 bit slots and are usually coloured black on the motherboard. -iSCSI Internet SCSI. The oldest of the SAN interconnect protocols. SCSI commands are sent inside IP packets. The receiving station takes the commands out of the packet and passes it to the SCSI controller, which makes the request to the storage. The result is packaged back up in an IP packet and returned to the originator. -ISDN Integrated Services Digital Network. See Digital Telephony. Enables the transmission of digitised signals over existing telephone network. A basic rate ISDN line has three channels - two 64Kbits/s B channels (Bearer channels) and a 16Kbps D Delta) data channel that is used for signalling third low capacity of about 90 to 110kbits/s. Primary rate ISDN consists of multiple B channels and one 64Kbps D channel. Two standards European and American. European standard is 30B + D to give the 2.048Mbps of an E1 line. In the US it is 24B + D to give the 1.544Mbps of a T-1 line. Signalling is carried out on the D channel. Data sent over the B channels is sent without framing information and with no error detection or correction. It is left to the end devices to deal with this. ISI Information Society Initiative. A DTI-led scheme, which represents the government's broad brush IT adoption program that aims to promote the use of computers and IT in general in all areas of modern society. -ISM band Industrial, Scientific and Medical band - 2.45GHz -ISO International Standards Organisation -ISO-13406-2 Standard for defective pixels in flat panel displays. Drafted in 1999 and finalised in 2001. It covers all ergonomic aspects of TFT monitors including uniformity of colours, contrast and brightness as well as reflectivity, flicker and pixel defects. The standard defines four types of defect. The first is where a whole pixel is continuously lit. This gives a white spot on a black screen. The second type is the opposite of the first - giving a black pixel on a white screen. The third is where there is a subpixel failure - resulting in a coloured pixel on a bright or dark screen, eg a blue dot. The fourth type of defect is referred to a fault cluster and is the number ©IPK30/04/17 of types one, two and three defects in a five by five pixel area. There are four classes to the standard and the pixel faults per million pixels are shown in the table below. Class Type 1 Type 2 Type 3 Type 4 with Type 1 or Type 4 with Type 3 Type 2 faults faults I 0 0 0 0 0 II 2 2 5 0 2 III 5 15 50 0 5 IV 50 150 500 5 50 Class IV allows as many as 500 defective pixels, class II between 1 and 5 and class I no defective pixels. ISO 27001 New formal standard against which organisations can seek independent certification of their Information Security Management Systems. Replaces BS7799 Part 2. -ISP Internet Service Provider. A company that hosts machines constantly connected to the Internet. You dial into one of their modems and connect to the network giving access to the Internet -ISR Interrupt Service Routine. -ITIL IT Infrastructure Library - a series of documents used to aid the implementation of a framework for IT service management. The framework is customisable and defines how service management is applied within an organisation. -ITR Intelligent Tag Reader -ITU-TSS International Telegraphic Union - Telecommunications Standards Sector. Replacement organisation for CCITT -IXC Interexchange carrier, or a service provider specialising in long distance transport services across multiple local exchanges JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ -Jabbering Continuously sending random data; normally used to describe the action of a station that locks up the network with its incessant transmissions. Often caused by a damaged NIC. Can also be used in connection with Ethernet networks. The 802.3 standard defines a minimum and maximum packet size. A jabber is a packet that is larger than the 1518 byte defined limit. -JANET The private network for the academic community in the UK. It is managed by UKERNA for the Joint Information Systems Committee (JISC) of the Higher Education Funding Councils for England, Scotland and Wales. -JANET-CERT JANET Computer Emergency Response Team. ©IPK30/04/17 -Java An object-orientated programming language that enables software developers to create interactive elements that work across operating systems. This makes Java an ideal language for Web programmers. Developed by Sun Microsystems in 1995. Intended to be hardware non specific An evolution of C++. Object orientated. Java is interpreted and the interpreter is called the Java Virtual Machine or JVM. A JVM has been developed for several different platforms. Java compiles to an intermediate format called byte code that should run on any JVM. Java can be embedded in a web page. -JavaScript A scripting language, similar to Java, which allows Web programmers to create dynamic content, such as interactive games or search engines on their Web sites. Produced in 1995 by Netscape for use with its Navigator browser. Its name was changed from Livewire to Javascript because its syntax resembled Java. -JAX Java API XML an open standard proposal for interfacing with event driven XML processors. -JCN JISC Committee on Networking. A sub-committee of JISC which is responsible for the UK networking programme for higher education and research. -JCP JANET Connection Point. -JCS JANET Customer Service -JCUR JANET Connection and Upgrade and Request form -J2EE Java 2 Enterprise Edition -JISC JANET Information Systems Committee -JIT Just In Time. Intermediate language run time compiler -JOD JANET Operations Desk. Based at ULCC, and provides a single point of contact for computing service staff to report faults on any of the JANET Operational Services -JPEG Joint Photo Experts Group. Supports both 16 and 32 bit images so ideal for photographs. Lossy compression. Can use 16.7 million colours at a much higher compression than GIF. -JRUN A development environment for Java-based server software. -JSP Java server Pages. A scripting language based on Java for developing dynamic web pages and sites. Often used on Solaris and Linux platforms -JVM Java Virtual Machine. Interpreter for Java. KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK ©IPK30/04/17 -KAK Worm virus. WWW.microsoft.com/technet/security/virus/kakworm.asp install security patch. Attaches itself to all outgoing messages; alters the registry; closes the PC at 5pm on the first day of every month. www.microsoft.com/technet/security/bulletin/ms99-032.asp -Kbps Kilobits per second -Kermit A file transfer protocol. When it breaks a file into packets, each packet is bracketed by control data. The receiving computer checks each packet's control data as it arrives and acknowledges to the sending computer. -Kernel The device drivers that enable hardware to communicate with software applications. The kernel sits between the hardware (such as hard drives or video cards etc) and software, and also provides a library of standard routines, such as for opening a file or changing user ID. -Keyboard plugs. 1 3 4 5 2 Keyboard Data Ground +5V Keyboard Clock Keyboard Reset DIN 2 4 5 1 3 Min DIN 1 3 4 5 LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL -LAMP Open Source web development program. Linux, Apache, MySQL and Perl, Python or PHP -LAN Local Area Network. A network of computers in a relatively small area. Each computer (or node) has its own operating system, but can access files or use devices such as printers or modems across the network. To link two computers enable NetBEUI, IPX/SPX and TCPIP. Primary network log-on set for Client for Microsoft Windows. Give each computer a unique name and make sure that they are both in the same workgroup. -LAN Manager A network operating system developed by Microsoft and 3Com for use with the OS/2 operating system. -LAPM -Laser printers Link Access Protocol and MNP 1-4 Based on the same principle as the photocopier. First laser printers made by Xerox. The digital signals turn on and off a beam of light which is generated by a ©IPK30/04/17 laser. This hits a spinning mirror which deflects the beam onto a photosensitive drum. The point at which the light hits the drum, a positive electric charge is produced and the toner attaches electrostatically to these areas. The paper then picks up the toner off the drum and passes through a heater or fuser which fixes the image to the paper. Instead of using a laser to generate the light, some printers have a row of tiny LEDs. LED/LASER printers The printers processor controls a light source that is projected onto a light sensitive drum. This creates a positive charge on the drum's surface at the points where the light hits, creating a pattern that will represent the output image. The drum rotates past the toner cartridge, upon which the negatively charged toner particles are attracted to the positively charged portions of the drum. These are transferred onto the negatively charged paper, which passes next to the drum after it has passed the toner cartridge. Finally the toner particles and paper are heated in the fuser unit to bond the particles to the paper so creating the image. It is the light source that differs in LED and laser printers. In a laser printer an arrangement of lenses and mirrors reflect and refract the beam across the surface of the drum. Since the drum is rotating, precise timing is needed to retain a straight horizontal beam path across the drum. Parallax correction is also used to keep the beam focuses at the edges of the drum. By contrast, an LED array is a relatively compact and sturdy arrangement that shines light through focusing lenses directly across the width of a rotating drum. This eliminates parallax and timing errors. As there are no moving parts, LED technology is more reliable than laser. Also a LED array can enable faster print speeds since multiple light sources shine on the entire width of the drum allowing it to rotate faster. Because of its compactness, LED technology comes into its own in colour printers. It can enable single-pass printing by employing four separate print head units each incorporating a LED array and a photoconductive drum, one for each toner, cyan, yellow, magenta and black. As a result LED colour printers are nearly as fast as monochrome printers. Colour laser printers have to pass the paper through the electrophotographic process four times, one for each of the four colours. Disadvantages of LED printers: the number of LEDs fixes the horizontal resolution of the printer. So resolution enhancement techniques can never be as effective as those of laser printers since the laser beam intensity can be varied. The quality of LED arrays also degrades with time as the intensity of individual LEDs weaken at different rates, leading to streaking and non-uniform printing across the page. This also is the reason why LED printers are inferior for producing graphics. To print in colour, the paper either has to make four passes under the photosensitive drum, one for each colour or there have to be four different toner hoppers around the same drum. To ensure that only the cyan toner goes to the cyan bits etc is usually done with different charging voltages. Charging corona Photosensitive drum Toner reservoirs Cleaning blade Fuser Paper path Transfer belt ©IPK30/04/17 -Latency This is the time it takes a hard drive to access data, not just find the data as in seeking and is based on the drive rotating half a revolution. The lower the figure the better. The time in ns or clock cycles between a request to read memory and the data being output. -Layer model -LBA The OSI Open Systems Interconnection model Large Block Addressing. Needed to work with drives larger than 504MB. -LBA Logical Block Addressing. - abandons the usual cylinder/head/sector divisions of a hard disk and substitutes a single address which is used to number each sector of the hard disk consecutively. -LCOS An expensive technology used in data projectors. Also known as DILA technology. Combines the use of LCD and DLP technologies to give a good image. Very expensive currently. LCOS is a reflective technology that constructs the image on a mirror substrate covering the chip. Rather that using thousands of individual mirrors to construct the image, the LCOS mirror substrate is coated with liquid crystals that can open and close to modulate the light in a similar fashion to LCD technologies. These projectors actually contain three LCOS ICs, on eof reach of the main colours. This means that it does not need a rotating spinning colour wheel. Very high resolution compared to the other projector technologies. -LDap Lightweight Directory Access Protocol. Network policy schemes from Microsoft, Novell etc. A lightweight replacement for the old X.500 mechanism that enables applications to access a directory service. It is used in identity verification and single sign-on applications. It defines the method by which directory data will be accessed; not how, or in what kind of database that information will be stored and manipulated. It is cross-platform and standards based, so it is not limited by hardware, operating system or database, and provides a basis for integration of directories within and between organisations. LDap-aware client applications use standard protocols and filters to request LDap servers to look up indexed data. LDap client applications and servers from different suppliers should not need to be customised to work with one another. In fact, beyond the use of the protocols and query commands, LDap does not specify how either client or server application needs to work. It originated at the University of Michigan in the early 1990s, to provide most of the functionality of X.500/X.519 without the need to implement a full OSI protocol network stack. LDap enables data kept in different directories managed by multiple applications to be unified and managed centrally. -LGMR Laser Guided Magnetic Recording. Used by Super DLT, which employs optical and magnetic methods to greatly increase the data storage capacity of cartridges. -Linear tape drives Or Longitudinal Serpentine technology. The data tracks run in parallel over the length of the tape and data is written sequentially until the end of the tape is reached. Then the read/write head simply moves up one track, and writes data in reverse until it reaches the beginning of the tape again. Because of the parallel layout, extra read/write elements can be put into the tape head to increase transfer rates and boost capacity. The technology tends to give better reliability, capacity and transfer rates. ©IPK30/04/17 -Line driver A DCE device that amplifies a data signal for transmission over cable for distances beyond the RS232/V.24 limit of 15.2m -Linker Or Linker loader is software which links two or more separately produced object code files (compiled programs) into a single program. The linker is also used to link object code programs with the library routines called within the programs. Library routines are simply additional object code programs -Link Layer Layer 2 of the OSI reference model. Also known as the Data Link Layer. -LINUX Created by Linus Torvalds. GNU recursive acronym for GNU's Not Unix. Linux is strictly the kernel of the OS. Little penguin called Tux. Linus Torvalds was a student at the university of Helsinki - had enrolled on a Unix course in the autumn of 1990. Being unable to afford Unix, but with access to the source code of a Unix-like OS called Minix, he wrote the device drivers for his own PC and gradually built up the kernel in 1991. It was released onto the web in 1991 and the first stand alone version was launched in 1992. -LINX The National Access Point for the Internet for the UK. Located in Telephone house in London's Dockland. Data rates of 3Tbps. -LLC Logical Link Control. A protocol developed by the IEEE 802 committee for data link level transmission control. The upper sublayer of the IEEE Layer 2 OSI protocol that complements the MAC protocol. IEEE 802.2. Includes end-system addressing and error checking -LLUB Local Loop Unbundling. Leasing out local copper cables to other Telecom providers -LMS Learning Management Systems. Tracks progress of students through lessons and provides reports to monitor the learners performance. -Logo.sys The Windows start up screen file/image. Needs to be 256 colours and 320x400 pixels. -Long file names Can be up to 255 characters in length. Can be backed up and restored in DOS using lfnbk.exe. Instructions for using lfnbk.exe are found in Windows95 Resource Kit help file Win95rk.hlp, which is in the Admin\Reskit\Helpfile folder of the CD. -Loopback Diagnostic test in which the transmitted signal is returned to the sending device after passing through all or part of the data communications link or network. permits the comparison of the returned signal with the transmitted signal. -Loose Tube Fibre compounds. Out door optical fibre cable. Filled with gel and other water repellent ©IPK30/04/17 outer jacket aramid yarn loose tube optical fibres strength member -LOSH/LSZH Low Smoke Zero Halogen cables have a special jacket, that when set alight does not pollute the atmosphere with harmful and toxic gases. -Love Bug e-mail virus. Some of its effects. resets IE startup page installs files love-letter-for-you.* Funny Love.* MSKernel32.vbs Winfat32.exe Win-bugsfix.exe It also steals your internet access passwords and e-mails them to an address in the Phillippines -Low Profile -LPIC The height of the drive is 1". Linux Professional Institute Certification -LTO Linear Tape Open. Back-up tape format. LTO3 gives up to 800GB compressed and up to 490GB/hr. Costs around £4k. The system is backed by IBM, HP and Certance. LTO Ultrium: Generation 4 offers a transfer rate up to 240MB/s based on 2:1 compression and a capacity of 1.6TB. Generation 5 will reach 3.2TB at 350MB/s and generation 6 will reach 6.4TB at 540MB/s -LU 6.2 A set of protocols that provides peer to peer communication between applications. -LZW A lossless method of picture compression - used in both GIF and TIF files. It works by employing an algorithm to find repeated pixel combinations and builds a table to represent them. The result is typically 30% smaller than the original. LZW was subject to a patent held by Unisys, but they do not intend renewing this when it expires. MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM -MAC address Medium Access Control address, often called the physical address. -Macro virus The most common kind of virus and account for about 80% of all infections. Usually applied to Microsoft Word and Excel documents. -Magistr Internet worm virus. Can erase all data from the hard disk. Deletes information in CMOS memory and flash the BIOS. Sent as a .exe e-mail attachment. The e-mail subject header and body text are randomly generated from documents on the hard disk of the affected computer. You should query the unexpected receipt of an e-mail about a random topic. -malware Generic name for all malicious computer code -MAN Metropolitan Area Networks ©IPK30/04/17 -Manchester Encoding Digital encoding technique specified for the IEEE 802.3 Ethernet baseband network standard. Each bit period is divided into complementary halves; a negative-topositive (voltage ) transition in the middle of the bit period designates a "1", while the a positive-tonegative transition represents a "0". The encoding technique also enables the receiving device to recover the transmitted clock from the incoming data stream. -MAPI Message Application Program Interface -MAPS Mail Abuse Prevention System - their web site provides advice on preventing relaying by mail servers. -Mark Presence of signal. In telegraphy, a mark represents the closed condition or current flowing - equivalent to a "1". -MAU Media Access Unit. A single device that combines the function of a transmitter and receiver. Also known as Multistation Access Unit. Used on a Token Ring LAN -MBR Master Boot Record is located at the very beginning of the hard drive (side 0, track 0, sector 1). The systems ROM BIOS bootstrap loads and executes the bootstrap loader contained in the MBR. This lets the system know which partition is the startup partition. -MBWA Mobile Broadband Wireless Access. Ieee P802.20. Operates in the 3.5GHz band and can provide 1Mb/s at up to 15km. Can link moving client devices travelling at up to 250km/hr -MC2 Memory Channel 2. Used for the fast transfer of data between clusters. -MCA Microchannel Architecture. A 32-bit slot expansion card introduced by IBM. Ran at 8MHz. -MCE Media Centre Edition - version of Windows XP with the Media Centre Application. -MCE Media Centre Extender -MCI Microsoft Control Interface - used with video cards. -MCP Media Communications Processor -MCP Microsoft Certified Professional -MCSE Microsoft Certified Software Engineer. -MDA Mail Delivery Agent. Delivers e-mails. The most common MDA is remote POP3. ©IPK30/04/17 -MDI Multiple Document Interface. Used by Office 97. See SDI -MEF Metropolitan Ethernet Forum - alternative to ADSL and DSL. -MEMs Micro-Electromechanical Systems. -Memory SDRAM, Synchronous DRAM was the successor to EDO and was near universal until recently. The main specification for SDRAM is its access time, in ns, and is usually the last number printed on the chips themselves. Early memory was 12ns and quickly improved to 10ns. 100MHz CPUs led to yet faster memory, usually 8ns. This led to the definition of the PC100 standard, with PC66 being used to refer to the older 10/12ns memory. PC133 led to 7.5ns and PC150 and PC166 is appearing. The most common form factor is the 168-pin DIMM. Memory supported by the various chip sets: Intel 440BX Pentium II/III, up to 1GB of PC133 Intel 810x Pentium III, up to 512MB PC133 Intel 815x Pentium III, up to 512MB PC133 VIA Pro133A Pentium III, up to 2GB PC133 VIA KT133x Athalon, up to 2GB PC133 ServerWorks LE High end Pentium III/XEON, up to 4GB PC133 ServerWorks HE High end XEON, up to 16GB PC133 SiS 630 Pentium III, up to 1.5GB PC133. RDRAM Rambus memory. Rambus Corporation. Speeds known as PC600, PC700 and PC800 and the form factor is the 184-pin RIMM. Intel is the only mainstream manufacturer to design for RDRAM. Intel 820x Pentium III, up to 1GB PC800 Intel 840x Pentium III, up to 4GB PC800 interleaved Intel 850x Pentium 4, up to 2GB PC800 interleaved DDR SDRAM This is the newest type of memory. Uses a lower voltage than regular SDRAM and exploits the PC clock timing signal to double the data rate transferred in a single clock cycle. Specified as PC1600 or PC2100 - referring to the peak data transfer rate in MB/s and the form factor is a 184-pin DIMM. Only three manufacturers support this chip set: AMD760 Athalon up to 4GB VIA pro266 Athalon and Pentium III variants up to 4GB ALi MAGiK/ALADDiN(4) Athalon and Pentium III variants up to3GB. In theory PC133 runs half a second faster than PC100. In practice compatibility issues with memory can lead to difficulties. Interleaving is awell established practice of increasing memory performance by addressingmultiplememory segments in parallel (like disk striping). For this modules have to be installed in pairs. Only works on boards that have even numbers of RAM slots. VIA and ALi DDR chipsets have the capability of addressing both SDRAM and DDR SDRAM but only ALi boards have both sockets. Major on Third - Major memory manufacturer mounted on a third party board. Major on Major - Major memory manufacturer mounted on a their own board. Registered memory - Used for high end/mission critical systems, where the data must arrive as intended. Called Registered because it contains a register that delays all data transfer to the memory module by one clock cycle to make sure that everything is there. Tends to be more expensive and slower than non-registered memory. Buffered memory - designed to handle large electrical loads in systems that have a massive amount of memory installed. ©IPK30/04/17 Expanded memory - divides memory beyond 1MB into small chunks called banks which can be used by DOS. Extended memory (XMS) - any memory beyond the 1MB limit. Can address the whole of memory without swapping banks in and out. Upper memory area - between 640Kb and 1024Kb used to hold device drivers instead of using conventional memory. Old 486 machines use 30 pin SIMMs (about 3 inches long). Usually installed in banks of four Pentiums use 72 pin SIMMs (about 4 inches long). Usually installed singly in 486s and in pairs in Pentiums DRAM dynamic random access memory. EDO RAM extended data output RAM. Provides a 10 to 15% speed improvement. SDRAM Synchronous DRAM. Uses the clock to harmonise data input and output on a memory module. The clock is in complete synchronisation with the cpu, thus reducing any lag between cpu requests and memory activity. RDRAM Rambus DRAM. Meant to be very fast. Cache memory. To get round the performance lag in DRAM, special high speed memory can hold data and applications and allows the cpu to have faster accesss than if they were stored in main memory. Cache memory works in conjunction with the main memory and the cpu using a separate controller. Level 1 cache is stored within the cpu. Level 2 cache is stored on the mother board. -Memory Test October 2002 PCA -MESH An any to any network in which a node is connected to virtually any other node in a collection of cross-connect links, implemented using OXCs. Can allow very efficient routing, but can be expensive to implement. -MGCP Media Gateway Control Protocol (MGCP) - also known as H.248 and is one proposed standard for replacing the older H.323 for the conversion of audio signals carried over the PSTN to packets for data networks. Developed by Telcordia and Level 3 Communications and has been accepted by the IETF as Megaco and as H.248 by the Telecommunication Standardisation Sector of the ITU. The older H.232 was previously okay for Lans but it did not scale to larger networks. The growth of VoIP has seen a need for a better protocol. MGCP is designed to make IP telephony devices cheaper because it eliminates the need for them being complex, processor intensive devices. It does this by using a media gateway controller to setup, maintain and terminate calls between endpoints. Part of this puzzle is to make sure that all endpoints involved in a communication are working at the same rate. MGCP's controller can determine the location of all end points and accurately calculate the media capabilities of each. In addition to voice, as the name suggests, the protocol can handle multi-point multimedia conversations, such as that found in video conferencing. -MIB Management Information Base. Information stored on networks by high end management systems like HP Openview. -Microsoft Formed by Bill Gates and Paul Allen in 1974. -Microsoft lifecycles. OS Win 95 Available August 95 Extended phase December 00 Non-support December 01 End of life December 02 ©IPK30/04/17 Win NT3.5 Win 98/98SE Win ME OS August 95 June 98/June 99 December 00 Available n/a June 03 December 03 Main Phase Win 2000 Pro Win XP Pro Win XP Home March 00 December 01 December 01 March 05 December 06 December 06 December 01 Jananuary 04 December 04 Extended support phase March 07 March 07 n/a December 02 January 05 December 05 Free online support Eight years + Eight years + Extended phase - Online support and paid for live support. Patches and downloads only available on business products. Non-support phase - No online or live support; only on line self help support available. End of life - All support ends. -Middleware Applications and servers designed to take content from otherwise incompatible back-end data sources and pass it to Web front-ends -MIDI Musical Instrument Digital Interface. The industry standard for the connection of a musical instrument to a computer. -MIDP Mobile Information Device Profile -MIME Multipurpose Internet Mail Extensions. Used for specifying Web content. -MIMO Multiple Input, Multiple Output. Often used in Voice over WiLAN. Uses multiple aerials and radios to send and receive signals on a single channel - so increasing bandwidth and range. This takes advantage of multipath signals. -MMAC Million Multiply Accumulates -MMC Microsoft Management Console. W2k server -MMC Multimedia Card. - Memory card. -MMU Memory Management Unit. -MMS Multimedia Message Service. Can send photos, voice clips and video clips. Not limited to the 160 characters of SMS. -MMX MultiMedia Extension. The MMX processor receives audio-visual data in parallel eight bits at a time, rather than one bit. It also includes a 32KB level 1 cache - twice the size of the classic pentium. -MNP Levels 1 - 4 Microcom Networking Protocol. Developed by Microcom Systems Inc. Enabled error-free async data transmission via a modem. ©IPK30/04/17 -MNP Levels 5 As above but also includes a data compression algorithm, which compresses by 2:1 -MOC Microsoft Official Curriculum courses -Modem Modulator/demodulator. A device which allows a PC to communicate and exchange information with other modem-equiped computers via normal phone lines. V17 fax operation at up to 14400bps. V22 1200bps full duplex - can transmit and receive simultaneously. V22bis 2400bps full duplex V23 1200/75bps Prestel V29 fax up to 9600bps. V32 9600bps full duplex V32bis Speeds to 14400bps V34 28800bps. -Moiré A flickering effect and is prevalent in screens predominantly featuring high contrast patterns. The best solution involves decreasing the focus, though altering the size of the viewing area can help. -Moire patterns Seen on monitors and woven linen and silk comes from the french word for Mohair. -Monitors. VGA Video Graphics Array VGA 640x480 16 colours. SVGA 800x600 SVGA(1024) 1024x768 enhanced 8514/A (IBM) 1024x768 (different to SVGA1024) XGA (IBM) 1024x768 CRT types Shadow mask - a metal sheet with thousands of fine holes in it, through which the electron beam passes before striking the screen. It blocks stray electrons increasing image sharpness but reduces the image brightness. Phosphors on screen shaped as dots Aperture grill - developed by Sony and Mitsubishi. The stary electrons are filtered out by very fine vertical wires which preserve the image brightness. Usually have a dark tinted screen which gives a higher contrast. Phosphors on screen shaped as rectangles/ Refresh rate - aim for minimum of 75Hz. TFT LCD displays:Image sharper than with CRTs Bright white fluorescent tubes provide back lighting and transistor driven liquid crystal elements filter and block the light to produce the image. Can only effectively display one particular screen resolution - known as Native resolution. Can go below native resolution but loses clarity - cannot go above native resolution. -Mono mode fibre These have inner core diameters of either 9µm and an outer core that brings the diameter up to 125µm. These only allow a single mode of propagation along the fibre. ©IPK30/04/17 -Moore Gordon Moore. In 1965 he originated the idea that microprocessor performance (chip density) should double every 18 months - Moore's Law. Later changed it to a doubling after two years. Co-founder of Intel in 1968. Intel released the 4004 processor in 1971 with 2250 transistors on the chip. This is dwarfed by the 42 million transistors on the Pentium 4 processor released in 2000. -Motherboards Abit albatron AOpen Asus ECS Gigabyte MSI Shuttle VIA Manufacturers www.abit.com.tw www.albatron.com.tw www.aopen.nl www.asus.com www.ecs.uk.com www.gbt-tech.co.uk www.msi.com.tw www.shuttle.com www.viamainboard.com -motherboard chipsets Two main chips are involved - called the North bridge and the South bridge. The North bridge is responsible for the high speed data transfers between the CPU, memory and the AGP graphics card. It can also have AGP graphics integrated. It also deals with data transfer to the South bridge. Most current chipsets have a 64-bit interface between the North bridge and memory. The CPU front side bus (FSB) speed is the speed at which the processor communicates with the North bridge and memory. AGP is an enhancement of the PCI bus, but as it is a point to point connection between the graphics card, CPU and memory it is a port not a bus. AGP 8x now runs at 533MHz. The South bridge is responsible for transfers to and from the slower devices such as PCI cards, hard disks, USB and Firewire devices. -Mount Rainier The latest adjustment to re-writeable media. Also known as CD-MRW. Designed to provide improved packet writing. Also allows CD-RW formatting in the background and data can be written to the disk straight away. Cluster size reduced to 2KB from 4KB. -Mouse Type: Serial 2-button mouse support, Hosiden connector, IBM PS/2 compatible. 1 Data I/O 2 Reserved 6 5 3 Ground 4 3 4 +5V DC (not fused) 2 1 5 clock I/O 6 Reserved Mouse originally conceived by Douglas Englebart at Stanfor University -MOW Multimedia over WAN ©IPK30/04/17 -M-pay Vodaphone's online payment service for transactions between 5p and £5 via the internet and mobile phones. -MP3 MPEG-1 Layer 3. ID3 header information is stored at the end of an MP3 file (see www.id3.org/id3v1.html for more details). The data starts 128 bytes from the end of the file. Consists of 30 bytes of Track, 30 bytes of artist, 30 bytes of album, 4 bytes of year and 30 bytes of comment. -MPEG Motion Picture Expert Group. A compression format for video enabling high quality picture sequences to be stored on disk. MPEG-1 created primarily for CDROM titles and was designed to deliver full motion video running at 24 to 30 frames per second. The video image was restricted to quarter screen size of 352 by 240 resolution. The audio component of MPEG-1 is used for MP3 audio files. MPEG-1 is used for recording video CDs. -MPEG2 The compression standard used on DVD video disks. High quality video and sound with reasonable file size. Provides broadcast quality video at full motion frame rates and full screen resolution of 720 by 480. This is the standard format used to create DVD film titles and is also used in many satellite broadcasting systems. MGEG-2 works by compressing groups of frames together, rather than treating the video as a series of individual frames. This makes them difficult to edit. There are exceptions, but MPEG2 typically breaks frames of video into three different types; I, B, and P frames. I frames or Intraframes, are the cornerstones of MPEG2 and are the least compressed. They are created by combining the two fields that make up a PAL signal into a single frame and applying an algorithm called DCT (direct cosine transform). This is the same algorithm used in JPEG compression, so an I frame is basically a JPEG picture. Although it is compressed, all the image data is contained within the I frame subset which allows it to be used as a reference point for other frame calculations. The frame is divided into squares called macroblocks, which are then converted into numbers that represent colour and light values contained in each 16x16 pixel section. The I frames reduce spatial redundancy, P frames (predictive) reduce temporal redundancy, i.e. pixels that remain the same from one frame to the next. Preceding frames are scanned for macroblocks that match up with ones in the current frame. If a macroblock is found that hasn't changed, it is replaced with a pointer that tells the decoder to repeat the earlier one. Alternatively, if a macroblock is the same but has moved to a different position (the camera is panning for example) the encoder replaces it with information that lets the decoder know where the original can be found and in which direction it is going (vector data). In static scenes, only a few macroblocks will change from one frame to the next. This allows more data to be discarded and so the P frame can be compressed by as much as 90%. The B frame (bilinear) describes how the encoder examines areas on preceding and successive frames to see if anything has changed. This again replaces matching macroblocks with positional and vector data, but the encoder can also calculate average values from I and P frames, essentially smoothing out differences between the two. This takes a long time to calculate but can provide compression up to 98%. GOP structure (group of pictures) describes the number and arrangement of I, B and P frames. The default structure for most encoders is a 12 frame GOP, which is IBBPBBPBBPBB before repeating. This is usually good enough for many video samples. If the video is detailed or fast moving then this can be shortened to a six frame GOP or less, i.e. IBBPBB. This increases the resolution but decreases the compression. -MPEG3 Motion Picture Expert Group, audio layer 3. A compression technology that is applied to music. ©IPK30/04/17 -MPEG4 The most famous implementation is DIVx. Uses the same GOP as MPEG1 and MPEG2. Often used by digital cameras to record video sequences. -MPI Message Passing Interface. Used with parallel processing clusters -MPLS Multi Protocol Label Switching. A way to keep all IP packets from the same voice or video session associated with each other in a common "flow", by adding a special label to the IP packet. A way of discriminating between packets so that traffic flows can be prioritised. It uses labels, or tags, containing forwarding information attached to IP packets by a label edge router at the edge of the network. Label edge routers perform packet analysis and classification before the packet enters the network backbone. Backbone routers (label switch routers) examine the label and forward the packet without making forwarding decisions. -MPPE Microsoft Point to Point Encryption. Used with PPTP. Based on RSA RC4 standard and supports 40-bit and 128-bit encryption. -MRAM Magneto-resistive random access memory. Non volatile - uses magnetism instead of an electrical charge to store data. Could lead to instant on computers -MRU Most Recently Used - programs -MSAU Multi station Access Unit. A device used in IBM Token Ring LANs to connect PCs and terminals in a star based topology. -Msconfig.exe System Configuration Editor. To disable fast shut down run msconfig and on General page click advanced. -msdos.sys Autoscan=0 Autoscan=1 Autoscan=2 Logo=1 Logo=0 BootMulti=0 BootMulti=1 Can edit to change Win95 bootup options. Never Scandisk run options on boot-up after improper shutdowns After prompt Without prompt Show screen Win95 logon screen Do not show Boot Win95 Run old Dos version -MSF Multi Service Switching Forum. Formed in 1998. Attempting to redefine switching on WANs. -MSIL MicroSoft Intermediate Language. Files are CPU independent and converted on the fly to run on the target processor by a specific just-in-time compiler. -MSN Multiple Subscriber Numbers ©IPK30/04/17 -MSO Multi-service Operators - eg telecos providing both TV and phones etc -MSSP Managed Security Services Provider -MTA Mail Transport Agent. (Can be SMTP). Communicates with other MTAs and DNS. Will queue any mail that cannot be delivered. -MTU Maximum Transmission Unit. Ethernet. The absolute maximum value is 1500. If the router cannot handle this then the data has to be fragmented increasing the time taken. -MUA Mail User Agent. The mail client used to send and receive e-mails. -Multicast A method of transmitting information to more than one target recipient simultaneously. -Multi-mode fibre These have inner core diameters of either 50 or 62.5µm and an outer core that brings the diameter up to 125µm. There are two varieties, Step Index and Graded Index. Both allow multiple paths for the waves to propagate. -Multipartite viruses Use a combination of techniques to spread itself, the most common type combines the methods of boot and file viruses. -Multithreading An operating system feature which allows an appropriately designed program to run several tasks concurrently. -MX records Mail Exchange records. Held in DNS and determines where e-mails are directed. Can have multiple MX records for a single domain. Useful if one e-mail exchanger fails. Give each e-mail server a different preference ranking, then is the MX with the lowest number (the best) is unreachable, the sending SMTP server will run through the list until it finds one to which the e-mail can be delivered. MX records should not be pointed directly at an IP address. It is an illegal call and does not work. The MX record needs to be directed to a specified hostname Formal Qualified Domain Name (FQDN) format eg mail.yourdomain.com which can then be resolved in turn into an IP address. eg. MX10 mail.domain.com MX20 mail2.domain.com MX30 mail3.domain.com with the MX10 record being designated to receive all of the e-mails normally. -MySQL Open source development of SQL NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN -NAK Negative acknowledgement. -NAO National Audit Office ©IPK30/04/17 -NAC Network Admission Control, part of Cisco's self defending network strategy, which uses Cisco's Trust Agent - a client based software agent. -NAP National Access Point. For the Internet. For the UK it is located at Telehouse in London's Dockland. Throughput around 3Tbps. -NAS Network Attached Storage. Storage devices that attach directly to a network and not through a server. Known as storage appliances -NAT Network Address Translation. Remotely connected (using Ethernet) storage, based on servers and RAID arrays. Often carried out by a router or proxy server and translates a local IP address into an Internet IP address. Document RFC 1631 defines NAT. Can be provided by either a router or a proxy server. NAT can be a problem if you want to host a web server. It will prevent any workstation on the Internet connecting to a web or FTP server on your network that's got a private IP address. The way around this is to creat a mapped link between the Internet and your LAN using a technique called 'port forwarding'. So for a web server all requests that come into the router on port 80 on its public IP address are mapped to port 80 of the private IP address of the web server. -Native Code A compiled executable in the machine code appropriate for the particular processor. -NetBIOS Network Basic Input Output System. Developed jointly with IBM and Microsoft. -NetBEUI NetBIOS Extended User Interface. Best suited to small to medium sized LANs -Netburst Microcode architecture used by Intel on their Pentium 4 and Xeon chips. -NetStumbler Program to gather information on WLans. www.netstumbler.com Free but only supports the Hermes chipset. -Netware -Network Network operating system from Novell Inc. ©IPK30/04/17 Internet 100Mb switches router cache engine firewall public web servers gigabit switches video streaming 100Mb switches 100Mb switches desk tops -Network Layer Layer 3 in the OSI model; the logical network entity that services the transport layer; responsible for ensuring that data passed to it from the transport layer is routed and delivered through the network. -Network topology The physical and logical relationship of nodes in a network; the schematic arrangement of the links and nodes of a network. Networks typically have a star, ring, tree or bus topology or some combination. -NEXT Near End Cross Talk. The interference between two pairs of cables used for transmit and receive. NEXT, the ratio of interference to transmitted signal, both measured at one (near) end of a terminated cable. -NFC Near Field Communication - developed by Philips and Sony. Allows transfer of data between their products. Carrier Frequency 13.56MHz. Distance up to 20cm and data rates of 212Kbps -NIC Network Interface Card. -NIC Network Information Centre. The people who register your domain name. -NISCC National Infrastructure Security Co-ordination Centre. Collated software bugs for the government. -NLIS National Land Information Service -NLPG National Land and Property Gazetter -Node A hardware device at which two or more communications lines meet. Each computer or other device on the network -Nominet The registry for .uk domain names. ©IPK30/04/17 -NOS Network Operating System. -NOSC Network Operations and Service Centre -Notepad To save files with a different extension to .txt, use Save As and put the complete file name in inverted commas. -NPMs Network processor Modules. -NPU Network Processor Unit -NRE Non Recurring Engineering -NRZ Non Return to Zero. Binary coding transmission with no return to neutral state after each bit is transmitted -NT-1 A device that converts the phone company's 2-wire ISDN U interface to a 4-wire S/T interface for compatibility with customer site terminal adapters. -NTFS New Technology Filing System -NTFS5 NT file system for windows 2000 -NTP Network Time Protocol - RFC 1305 -NTSC National Television Standards Committee. American video standard. Videos play at 30 frames per second. -NTU Network Termination Unit. -Null modem A device that connects two DTEs directly by emulating the physical conditions of a DCE -NUMA Non-Uniform Memory Access - a type of parallel processing architecture in which each processor or small group of processors has its own local memory but can also access memory owned by other processors. -NVP The nominal velocity of propagation of a cable is the speed that a signal passes along a cable as a percentage of the speed of light. Many NVPs are between 60% and 70%. -NX No eXecute. Built into AMD 64 bit processors. Limits a buffer overflow attack possibilities, which is where the computer's buffer memory space is overwhelmed with data and so can be made to execute malicious code. OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO ©IPK30/04/17 -OADM Optical add-drop multiplexer. An optical extension of a common SONET element called add-drop multiplexer, this is a piece of equipment that allows wavelengths to be added or dropped at particular node points. -OB10 Open Exchange's electronic invoice delivery service which has received Custom and Excise agreement to stop printing out invoices for VAT records. -Object code The compiled version of the source code written in machine code. -Object Orientated A language that lets you encapsulates program elements as objects. -ODBC Open Database Connectivity. Designed to present a programming interface to application programs that is independent of the underlying database implementation, i.e. an application can talk to a database connection and not know what the underlying database implementation is. -ODP Open Directory Project resources for many large sites, eg google. http://dmoz.org. powers core directory -OFDM Orthogonal Frequency Division Multiplexing. Uses multiple carriers to increase data rate on Wireless connections. -OGC Office of Government Commerce -OHCI Open Host Controller Interface. Used on Firewire. -OIS Optical Image Stabilisation. Used to reduce camera shake in camcorders. It uses motion sensors within the lens itself. When these detect camera movement, they trigger a small actuator that makes tiny adjustments to an internal lens, redirecting the incoming light and helping to reduce camera shake. Also see DIS -OLAP On Line Analytical Processing. Developed by Ted Codd. -OLE Object Linking and Embedding. Connects data between two files. Data in a linked destination file automatically updates when changes are made to the source file, but does not duplicate the information which is in that file. Embedding, on the other hand, creates a copy of that information (so using up hard disk space). Modifying data in the destination file does not affect the source file directly. -OMA Open Mobile Alliance. -OMAPI Open Mobile Application Processor Interfaces. - offers access to any service on any network using any kind of mobile terminal. -Open Access Internet Time Servers. - UK www.ntp.cis.strath.ac.uk www.ntp2a.mcc.ac.uk www.time-server.ndo.com ©IPK30/04/17 -Open Air Wireless standard 1.5Mbps. -optlog.txt In Windows Applog folder. Records the frequency with which programs on a PC are used. -ORB Object Request Broker - Allows communication between objects of independent language or platform -OSA Office Startup Application. Carries out initialisation tasks to help office load faster -OSFI Open Standards Fabric Initiative. Formed by five leading Fibre Channel switch makers. -OSI Open Systems Interconnection. An open systems architecture developed by the ISO to provide a means by which many different sorts of systems can communicate together efficiently and economically. -OSI Model Open Systems Interconnection Model. A seven layer model defining the way systems communicate. Provides a structure into which internationally agreed standards can be fitted. Each layer represents a function or group of functions from the 'Application' layer (7) that provides a 'window' for the operating system, to the Physical layer (1) that provides the transmission medium. Layer 1 Physical This layer puts raw data over the communication channel. This layer is largely responsible for the mechanical, electrical and procedural interfaces. Layer 2 Data link This breaks the data up into frames instead of sending it as one long stream. Frames are transmitted in sequential order and acknowledgement frames returned to prove receipt of data. It is up to the data link layer to solve problems caused by damaged, lost and duplicate frames. Also used to deal with transmission rate problems where a fast transmitter floods a slow one Layer 3 Network This controls the operation of the subnet and is mainly concerned with routing packets. Can be based on static routing tables or determined for every packet. Also has facilities for providing billing information to enable operators to charge for network usage. Layer 4 Transport Provides a method of communication between the session and network layer. It takes data from the session layer, breaks it into smaller units and passes them onto the network layer, making sure that the pieces arrive in the right order at the other end. It is an endtoend layer; an application on the source machine has a conversation with an application on the destination machine using the message headers and control messages. Layer 5 Session Allows machines to set up sessions between themselves. Also an end-to-end layer. A session performs tasks such as transferring a file. It manages the dialogue by specifying if the conversation can occur in both directions at the same time. If not it manages whose turn it is. The session layer also has to cope with synchronisation in the case of a system crash - so allowing file transfer to continue from the point it left off. ©IPK30/04/17 Layer 6 Layer 7 Deals with data syntax and semantics, e.g. encoding data. Contains a variety of protocols for communication - mapping user commands onto real protocols. (Session and Presentation layers rarely used by any applications). Each layer has its own header and the payload of the higher layers. The Internet Protocol Layer 3. The header contains the source and destination address plus the Payload (i.e. layer 4 and above). Layer 4 protocols. UDP User Datagram Protocol: Only added value is addressing of ports on host. TCP Transmission Control Protocol. Connection Orientated - establishes a connection between the two hosts. Each packet has about 40 bytes of header information. Layer 3 (IP) header is 20 bytes, 8 from layer 4 and 12 from layer 5. -OSO Presentation Application Overscan protection -OSPF Open Shortest Path First. A protocol used by routers on an IP network. Now being used in preference to Routing Information Protocol (RIP) which is an ageing protocol. It is used when a router detects a change in the network. The change is automatically sent to all machines in the same network to keep routing tables updated and identical across the network. OSPF only sends the specific changes and only does so when the changes occur, not every 30 seconds like RIP. -OTDR Optical Time Domain Reflectometry -OTP Open Trading protocol. Backed by Mastercard, Digicash and Netscape - aims to produce a consistent web based environment for e-commerce transactions. -OTP One Time Programmable -Outlook To export to Outlook 2000 and XP use the backup add-on from http://office.microsoft.com/downloads/2002/pfbackup.aspx -OXC Optical Cross-connect. This is the true system level optical switch, employed primarily in long distance networks, that can shift services from one wavelength to another, thus representing a key target system to utilise a tuneable laser PPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPP -P2P Peer to Peer -P4 Old 423 pin New 478 pin -P55C Intel's code name for the MMX processors. -Packet This is a unit of data, which is typically a part of a file, prepared for transmission across a network. Has the following sections. Start delimiter Destination address ©IPK30/04/17 Source address Type of data Data (length) CRC (error checking) End delimiter -PAL Phase Alternating Line. Videos play at 25 frames per second. -Palladium Microsoft Security Offering. Relies on Trusted computing -PAN Personal Area Network. -Parallel Port A plug and socket connection that can transfer a complete byte at a time. Speeds range from 40Kbytes/s to more than 1Mbytes/s. 25-hole female connector. Four types of parallel ports, unidirectional, bi-directional, EPP and ECP. To check which modes are supported, look in the peripherals section of the PC's Setup program. Unidirectional or SPP. Data flows outwards only at 40-50Kbytes/s. Bidirectional. Two way communication at around 100 - 300Kbytes/s. EPP Enhanced Parallel Port. Transfer rates of around 400 - 1000Kbytes/s. It provides the best possible performance that the port has to offer. When selecting EPP in System Setup, choose version 1.9 if possible. ECP Enhanced Capabilities Port. Improves both speed and two way communication between device and computer. When selecting ECP in System Setup, you will be able to select a DMA channel. Avoid conflicts by checking device manager for free DMA channels. If you can't fix the conflict use bi-directional mode. Standard Parallel Port Resource Settings. LPT0 IRQ7 3BC LPT1 IRQ7 out H378 LPT2 IRQ5 out H278 25 -way female D-type connector 13 1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 25 -STROBE (O) D0 (I/O) D1 (I/O) D2 (I/O) D3 (I/O) D4 (I/O) D5 (I/O) D6 (I/O) D7 (I/O) -ACK (I) BUSY (I) PE (I) SLCT (I) -AUTOFDXT (O) 14 ©IPK30/04/17 15 16 17 18 - 25 -ERROR (I) -INIT (O) -SLCTIN (O) GROUND -Parity Bit A bit that is set to "1" or "0" in a character to ensure that the total number of "1" in the data field is even or odd as desired. -Parity check The addition of non information bits to make up a transmission block that ensures that the total number of "1"s as always even (even parity) or odd (odd parity). Used to detect transmission errors. -PAS Partial Attribute Set - part of Active Directory. -Password Adding a three character password before executing the rest of the batch file. Save the following text as Getkey.scr, making sure to include the blank lines before RCX and after Q: N GETKEY.COM A 100 MOVE AH,0 INT 16 MOVAH,4C INT21 RCX 8 W Q Now enter the command Debug&It;Getkey.scr to create Getkey.com. Then place Getkey.com in a folder on your path. Getkey waits for a keystroke and returns the corresponding ASCII code. The following batch file uses Getkey to detect the passwprd AOK (case sensitive). TOP ECHO Enter password. SET K= GETKEY IF ERRORLEVEL 66 GOTO Not 1 IF ERRORLEVEL 65 SET K=%K%x :Not1 ECHO * GETKEY IF ERRORLEVEL 80 GOTO Not2 IF ERRORLEVEL 79 SET K=%K%q :Not2 ECHO ** GETKEY IF ERRORLEVEL 108 GOTO Not3 ©IPK30/04/17 IF ERRORLEVEL 107 SET K=%K%j :Not3 ECHO *** IF '%K%'=='xqj' GOTO OK GOTO Top :OK ECHO Password OK Consult an ASCII table and change the numbers to select a different password. -Password XP To remove passwords. Create a bootable floppy or CD. Use the offline NT Password and Registry editor (http://home.eunet.no/-pnordahl/ntpasswd Create bootable disk and follow the instructions. -PBCC Packet Binary Convolution Coding. Texas Instruments solution to IEEE802.11g -PBX Private Branch Exchange. -PC-DOS IBM's version of MS DOS. -PCI Peripheral Component Interconnect. This is the standard bus design for computer motherboards and expansion slots that can transfer 32 or 64 bits of data at one time. -PCI Express Serial bus - needs new cards. Offers increased bandwidth up to 80Gb/s. Enables direct connection to high bandwidth adaptors without the expense of an added I/O bridge chip. Intel chipset named Lindenhurst for servers and Turnwater for workstations. -PCI-X Parallel bus - accepts older cards -PCL Printer Control Language. Used by HP with its laser printers. The information, resolution, typeface and paper size are transmitted to the printer, which interprets the instructions and converts the data into a raster or bit mapped image, and the image is then printed out. Hence the need for a powerful CPU and generous amounts of memory in a conventional laser printer. -PCMIA More commonly known as a PC card, expands a computer's capabilities via a credit-sized card connection. Mainly used on portable computers. Personal Computer Memory Card International Association. Founded in 1989. The standard features: 68 circuit pin and socket, 5.4 by 8.6cm 1.27mm mating interface, 5V working, Polarisation key for correct insertion, 3 mating pin length (first mate last break) (3.5/4.25/5.00mm), 10000 mating cycles. There are three physical sizes of cards that differ only in thickness: 3.3mm, 5.0mm, 10.5mm. Type 1 cards, RAM, flash memory etc, Type II cards, IO devices, ©IPK30/04/17 Type III cards Hard drives, radio comms devices etc. Can interface with both 8-bit and 16-bit buses. Support physical access to up to 64MB of memory. People Can't Memorise Computer Industry Acronyms. -PCR Phase Change Rewritable - A rewritable CD in which the laser momentarily melts the crystalline coating on the disk, which then quickly cools to form an amorphous spot with lower reflectivity. To erase the data, a medium power laser beam can be used to cause re crystallisation. -PDA Personal Digital Assistant. -PDL Page Description Language -PEAP Protected Extensible Private Network -Peering Interconnections between networks, usually on an ISP level. Good quality peering means better Internet access for the end user -Peer to peer Links computers together, but has no central server. -Pentium Launched in 1993 by Intel to replace the 486. The first Pentiums were made with 0.8 micron (800nm) technology and had 3.1 million transistors operating at 60MHz. There were four architectural changes Pentium Pro, II, III, and IV and ended with one version pf the P4 called 'Cedar Mill' built with 65nm technology that has 188 million gtransistors running at 3.6GHz. All new chips will be called 'Core 2 Duo'. -Pentium 4 Early ones used a 423 pin socket, but the newer ones use a 478 pin socket. -Perl Practical Extraction and Report Language. A high level language derived from a wide range of sources including C and the UNIX shell. Can be downloaded free from www.perl.com Created by Larry Wall in 1987 but has been developed by a global community. Current version is Perl5.8 -PFA Packet Flow Acceleration. -Phishing Attempts to trick recipients into revealing passwords and bank details. -PHP PHP Hypertext Preprocessor. A scripting language used for developing dynamic web pages and sites. Typically used on Solaris and Linux platforms. Originally written in 1994 and completely rewritten in 1997 by the founders of Zend. -phreaking A similar practice to hacking but where telephone calls are made on a PBX system that bypasses the charging system. -PHY Physical layer Device ©IPK30/04/17 -Physical layer The lowest (first) layer in the OSI model; responsible for the physical signalling, including the connectors, timing, signal forms and other related matters. -PIMF Pairs in Metal Foil cables are a type of shielded cable where each of the individual pairs are contained in a foil sheath. This type of cable provides maximum isolation between the individual pairs, or minimum cross talk losses. Cat7 cables are PIMF cables with an additional overall shield, usually a braid. -PING Packet InterNet Groper. Written by Mike Muuss. A way of measuring the Internet's performance between yourself and Internet sites. Results usually expressed in milliseconds. To use click Start, Run and type ping server. e.g. ping ftp.eudora.com The ping command is used to send an ICMP (Internet Control Message Protocol) echo request message to a target host. It sends a packet from one device, attempts to bounce it off another and listens for the reply. A prompt reply means that the bit of the network between pinger and pingee is working. To test a PCs loopback address - a virtual IP assigned to all NICs when TCP/IP is installed. Its IP is always the same - 127.0.0.1. Pinging this address from the PC shows that the NIC is configured and working. Ping normally only sends four packets by default. The Ping command has the -t parameter thatconfigures it to continuously ping the target device ping -t 127.0.0.1 To pause it and display the statistics press Ctrl Break and to end it press Ctrl C Testing DNS can be done by pinging the name of a remote host eg ping www.webaddress.com Even if the DNS server does not respond to ping requests the result will still give the IP address for that URL, which tells you that the DNS is working. -PKC Public Key Cryptography. Works by: when the cryptography software is first set up it generates a pair of keys. One is a private key which is kept secret and guarded with a password phrase. The other is your public key which can be distributed widely. Ideally others should sign it digitally to ensure that messages do not become corrupt. The public key is used for encryption and signature verification. The private key is used for decryption and signature generation. Two examples of these are Turnpike and PGP (Pretty Good Privacy). -PKI Public Key Infrastructure. -Plasma Screens Consist of two thin layers of glass between which is a mesh of minute pockets of compressed gas - pixels. Each of these pixels have sub-pixels, or phosphors in the three primary colours, each of which is individually controlled. When the gas is electrically charged it turns to plasma and UV light. The reaction of the UV light with the phosphors causes the coloured light to be emitted. Produces a high contrast, fast picture. Susceptable to screen burn and get hot. -PLCP Physical Layer Convergence Protocol. Used in IEEE802.11b -Plenum Cables Used in the space above false ceilings or below an access floor. Produces very low levels of toxic fumes when burnt. Often coated in Teflon. -PMD Physical Media Dependent -PMD Polarisation Mode Dispersion 40G optical fibres ©IPK30/04/17 -PNG Portable Network Graphic. Invented by vendors in 1995 to avoid paying royalties to UNISYS for .gif technology. Offers better compression than GIF, a far wider colour spectrum and supports variable transparancy. -POE Power Over Ethernet - IEEE802.3af POE hubs send out a pulse at 20mW and 802.3af devices will deflect back with a 25k resistor built into the port. If the signal is not deflected, the hub will not attempt to deliver the full power. The absolute maximum power per port is 15.4W at 48Vdc.In practice, the maximum power is 12.95W, limited by the resistance of the cables. Can be provided over CAT5 and CAT6 cable for up to 100m. POE also referred to as Data Terminal Equipment (DTE) Power via Media Dependent Interface (MDI) Power over Ethernet Plus, IEEE802.3at is being considered and is expected to be ratified in 2007. It is likely it will deliver at least 30W. -Poledit Windows 95 and 98 policy editor. Found on W95 and W98 CDs in \tools\reskit\netadmin\poledit. Run poledit.exe, double click Local User, System, Restrictions and check Only run allowed Windows applications. Click Show, then Add and enter the executable filename of each program. Better to run Poledit from a separate disk or any one can then alter files! -Polling A communications technique that determines when a terminal is ready to send data. The computer continually interrogates all of its attached terminals in a round robin sequence. A terminal acknowledges the poll when it has data to send. -PoP Point of Prescence. The location of the nearest node for an ISP, this is the number dialled to connect to the Internet. -POP3 The Post Office Protocol (version 3) is the most widespread Internet standard for e-mail software to retrieve messages from a mailbox held on a mail server. E-mails are stored on a POP3 server at the ISP and then down loaded into and read by a POP3 client e.g. the Bat! or Outlook Express. -Polymorphic virus Changes itself each time it spreads. Because polymorphic viruses' signatures change, usually randomly, the common signature scanning techniques often fail to find them, antivirus packages must rely on heuristic technologies to detect them. -Port Used for connection requests and exchange of data with servers. If the IP address is considered to be the country, county, city street and house number, then the port can be considered to be the intended person in the house, e.g. Mr Smith. There are 65535 possible ports. The first 1023 are the system ports and will generally be used by root processes or programs executed by privileged users. The port is the addressing mechanism used in both TCP and UDP. It identifies the process on a system addressed by the IP address to which the TCP segment or UDP datagram should be delivered. Number of ports can be doubled using UDP (User Datagram Protocol) Port 21 FTP Port 23 Telnet Port 25 SMTP Send Mail Port 53 DNS Name Service Port 80 Web HTTP ©IPK30/04/17 Port 110 POP3 Retrieve e-mail Port 111 Port mapper service Port 119 NNTP News Port 123 NTP Network Time Port 135 Windows Messenger Service Port 135 DCom services, RPC Port 137 NetBeui, Also Windows Messenger Service, RPC Port 138 Windows Messenger Service Port 139 NetBeui, Windows Messenger Service, RPC Port 443 Secure web HTTPS Port 445 Windows Messenger Service, Microsoft Cifs file sharing Port 1433 SQLsnake a SQL worm infecting SQL servers. Port 1434 SQL server Port 1494 Citrix Meta frame Port 3128 Web cache Port 3389 MS Terminal Server Port 5190 AOL Port 6667 IRC Internet Relay Chat Port 8080 Web cache Port 17300 Kuang2 back door SunSeven 1234, 2773, 6713, 7215, 27374, 27573, 54283 Back Orifice 8787, 31337, 31338, 54320, 54321. A good list of Trojan ports can be found at www.sans.org To obtain a list of listening ports - type netstat -a www.sysinternals.com/ntw2k/source/tcpview.shtml -port forwarding when a port on a router is opened and then assigned a specific IP address -POST Power On Self Test. The first process a PC runs when it is switched on which checks memory, processor, graphics etc. A series of beeps indicates if errors are found. One beep usually means that all is well. -PostgreSQL The leading alternative database to MySQL in the LAMP open source development and deployment platform. It focuses on providing rich features and standards compliance. It is becoming a serious option for enterprise databases. It began in 1986 at the University of California, Berkley. Its original author was Michael Stonebraker, the creator of the Ingres relational database management system. Postgres means "after Ingres". -PostScript A page description language developed by Adobe Systems that describes each element as a vector pair, rather than telling the printer where to place each dot of ink or toner. It is more suited to graphics printing and has wider applications than PCL as it can produce better quality output at higher print resolutions. -PowerSum Applied to NEXT and ACR. Used to make measurements when data transmitted on all four twisted pairs. n ( dB )n PSNEXT 10 log 10 10 10 n 1 Power demands. ©IPK30/04/17 Motherboard Low end CPU Mid range to high end CPU RAM PCI graphics or sound card Low to mid range graphics card High end graphics card IDE hard disk Optical drives -PPC 15-20W 20-50W 40-100W 7W/128MB 5W 20-60W 60-100W 10-30W 10-25W Partial Private Circuits - last mile hardware connections for broadband connections -PPGA Plastic Pin Grid Array - used for Celeron chips with integrated level 2 cache memory. Socket 370. -PPP Point to Point Protocols. -PPTP Point to Point Tunnelling Protocol -PRI Primary Rate Interface Microsoft - VPNs -Printers Toner a health hazard. Clean up with a cold damp cloth. Not vacuum cleaner or hot water (melts toner). Alternative drivers on the W95 CD in Drivers\Printers\etc. There is also the Enhanced Print Trouble-shooter tool epts.exe on the W95CD in Other\Misc\Epts folder Inkjet Printers. Developed in early 1980s. Canon invented the technology and was the first to produce a 'BubbleJet' printer. CMYK cyan, magenta, yellow and keystone black. Inkjets use one of two methods to eject the ink from the cartridge, either they heat the ink or they use a crystal to squeeze out a single drop. Both methods use similar cartridges, with a well for the ink and a head for each colour, made up of around 50 nozzles through which the ink is dropped. With the heating method, a small resistor within the nozzle is heated. This heats the ink to around 100oC and as the ink expands, a drop is squeezed out of the nozzle and onto the page. The ink has to be heated and cooled thousands of times per second, so it must remain the same consistency under heat. The other method, known as piezo electric technology, uses a crystal instead of a resistor. Again, it sits in the nozzle acting a little like a valve. A small electric charge is applied to the crystal and the crystal twists, releasing a small drop of ink onto the page. Epson is the only manufacturer to use this technology Photo printers will generally use more than the four colours, CMYK, using instead six or seven inks. They will always include light cyan, and light magenta. Canon also includes a second shade of black. Dithering This is the process which uses dots in patterns to create different colours. Half toning. This process involves laying down larger or smaller dots to create a more realistic image ©IPK30/04/17 Streaking This is when the printer misaligns the lines of print, leaving out a small amount of the page, which shows through as a thin white line. -Print folders Create the following batch file called dirprn.bat using Notepad and save in Windows folder. dir>\dirlst.txt notepad /p \dirlst.txt del \dirlist.txt In Explorer find the batch file, right click it and choose Properties. Click on the Program tab. Change the Run Option from Normal window to Minimised. Check the box for close on exit. Click OK to close the Properties dialog box. In Explorer now select View, Folder Options. Click the File Types tab. Select the Folder file type and click the Edit button. In the Edit File Type dialog box, click New. For Action enter Print. For Application used to perform action enter c:\windows\dirprn.bat"%1" Close all of the dialogue boxes with OK. When you right click on a folder or drive icon in Explorer, you should find a Print option in the pop-up menu. -Print Server -Processors Manages access to shared network printing resources. 32 bit 80x86 can only address 4GB of memory unless bank switching is employed. 1984 Bill Joy and Dave Patterson start working on RISC processors. 1985 Intel introduces the 386 microprocessor 1987 The first SPARC processor is born. 1991 Intel introduces the 486SX. Texas Instruments release the SuperSparc. MIPS Technologies introduce the R4000. 1992 Digital launches the Alpha 1995 Sun introduces its first 64-bit processor, the UltraSparc. Intel releases the Pentium Pro. 1997 Intel Pentium II and Xeon released. 1999 AMD introduce the Athalon, Intel releases the Pentium III 2000 Transmeta launches the Crusoe. Intel releases the Pentium 4 IBM introduces the Power4 chip 2001 Intel releases the Itanium. The Itanium breaks away from the 80X86 instruction set. It uses a new instruction set called EPIC (Explicitly Parallel Instruction Computing) and can perform a number of tasks within a single clock cycle. It can address significantly more memory than 32 bit processors. -Profile Used in Bluetooth to define certain applications, such as file transfer or headset communications. Two Bluetooth devices need certain profiles in common to work together. -Promiscuous mode When a network adaptor processes all received frames. Used in bridging -Protocol The rules that govern computer communication ©IPK30/04/17 -Proxy server A server that sits between the browser and a Web server, which monitors all requests that pass through it. The proxy server intercepts all requests and checks that it does not already have the requested page stored on the hard disk. If it has, then the proxy server returns the requested Web page from its own hard disk. If the proxy server doesn't have the requested page, then it forwards the request to the web server. Proxy servers speed up internet access for large numbers of users, and can also be used by companies to filter out requests for unsuitable web pages. -PRML Partial Response Maximum Likelihood. An advanced detection method used on hard drives heads to improve data transfer rates and increase how much data can be stored on a drive's platter. -PSACR -PSELFEXT -PSNEXT PowerSum for ACR PowerSum for ELFEXT PowerSum for NEXT -PSTN Public Switched Telephone Network. A circuit is dedicated for the whole time of the call whether information is being sent or not. Restricted to the frequency range of 300Hz to 3200Hz as it is all that is needed for voice. -PTO Public Telecommunications Operator -PVR Personal Video Recorder -PXE Pre boot eXecution Environment. Part of Intel's open wired for management specification that automates client management. It allows a PC to boot remotely from an image stored on a server. PXE has a wake-on Lan element that allows an administrator to remotely power a computer by sending a signal to the network card. PXI-Express Based on CompactPCI. The specification was ratified in August 2005. Uses the same standard mechanisms defined in the PCI plug-and-play specification for device discovery and configuration. The basic physical layer consists of an ac coupled LVDS pair for RX and TX and utilises 8b/10b encoded and de-emphasis. The transmit and receive pair together are called a lane. The initial speed of 2.5Gb/s provides a nominal bandwidth of 250MB/s in each direction per PCI Express lane. This rate represents a two fold to four fold increase over most regular 32-bit 33MHz devices, and unlike PCI where the bus bandwidth was shared among devices, this bandwidth is provided to each device. The controller is capable of supporting up to a x16 PCI Express link plus a x8 link providing a total of 6GB/sbandwidth to the PXI backplane, which is a 45 times improvement in PXI backplane throughput. QQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ -QBasic Screen 12, VGA screen. Q basic program from Maxim Elektor July/ August 2000, page 35 -QCIF system Quarter Common Intermediate Format - Video compression ©IPK30/04/17 -QIC Quarter Inch Tape. Back-up tape format. Stationary read/write head, tape speed can be up to 120in/s. Data is written to one of 44 straight tracks in one direction before the mechanism reverses and records information on a parallel track in the opposite direction. Storage capacity depends upon the length of the tape. Access times are slow but data transfer rates can be up to 6Mb/s -QoS Quality of Service - a term used to describe the performance properties of an ATM service, especially guaranteed throughput level. -QWERTY keyboard layout designed in 1868 by typewriter inventor Christopher Sholes RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR -RAB RAID Advisory Board -RAC Remote Access Concentrator -RAD Rapid Application Development. Combine together pre built components with just a bit of extra code. Microsoft. -RADIUS Remote Authentication Dial In User Service. part of W2k VPN -RADSL Rate Adaptive ADSL - manages to provide a connection over a greater distance than standard ADSL - 5.5km rather than 3.5km -RAID Redundant Array of Inexpensive (or Independent ) Disks. Some redundancy of storage space. Many RAID controllers offer a large data cache. Level 0 simple data striping. The storage strategy involves combining multiple drives into a single logical data volume. The data are then interleaved among multiple disks. Having multiple drives service data yields an increase in performance over non-array disks because the data is being written in parallel. Level 1 data mirroring. This level of RAID involves a redundancy of storage devices. Data are written to two separate disk drives. If one fails the other is available to service data requests. Good data protection, but doubles the number of devices needed. Level 3 involves data striping as does level 0, but uses an additional device (drive) to hold parity information that can be used to reconstruct the data stored on any of the other storage devices. The overhead of RAID level 3 introduces a performance penalty that makes it unsuitable for applications with intensive I/O activity. Level 5 also uses parity to reconstruct data on a failed drive, but distributes the parity information on the data drives. Provides better performance than RAID 3, needing less hardware, but is still slower than RAID 0. Level 6 designed to accommodate the loss of two drives simultaneously, or to handle a disk failure during a data rebuild after an initial failure -RamBoost PC-DOS version of MemMaker -RAMBUS See RDRAM ©IPK30/04/17 -RAMDAC RAM digital to analogue converter oversees the data transition from graphics card to screen. -RAP Reconfigurable Algorithm Processing -RARP Reverse Address Resolution Protocol. Used to give a machine an IP address when it knows its Ethernet address. This is often the case when a diskless workstation boots up. In this case a RARP server responds to the request and gives the machine its IP address. However RARP broadcasts only reach as far as the router. This means that the requesting station has to be on the same network as the RARP server. A better protocol is to use Bootp, which uses UDP to span routers. Bootp also sends out additional information including a file to boot from, the IP address of the default router, and the subnet mask. -RAS Remote Access Server -Rat Attack Remote Access Trojan attack e.g. Back Orifice -RAVE Real Animated Vector Effects -RAW An image format, which is essentially a copy of the uncompressed image data produced by the camera. Large file size. -RCP Real-time Control Protocol - used in VoIP. Complements RTP by monitoring the quality of the end to end link. -RDBMS Relational DataBase Management System -RDF Resource Description Framework - method of processing meta data on the web i.e. data about data. e.g. Intelligent bookmarks that update in tandem with the site referenced. -RDMA Remote Data Memory Access. Used in SANs -RDRAM Rambus Dynamic Random Access Memory. Favoured by Intel. Lower cost alternative to DDR RAM. It has four power modes: Power Down mode uses no energy at all, Nap mode uses very little power, Standby mode uses about 20% of the power used when it is in its active state or Read/Write mode. Originally developed using Rambus signalling levels (RSL) to provide faster operating speeds than available through DRAM devices. See RIMM -Record -Recovery Console A row in a database table. Use when XP will not even start in Safe mode. ©IPK30/04/17 -Refresh rate How many times per second the image is updated on a monitor. Aim for at least 75Hz or preferably 85Hz. -Registered Owner Hkey_local_machine\Software\Microsoft\Windows\CurrentVersion folder. Two separate entries - Registered Owner and Registered Organisation. Double click to edit. -Registry Microsoft reg clean utility. Removes unused or corrupted registry keys. ftp.microsoft.com/Softlib/MSLFILES/Regcln41.exe Registry clean utility - www.microsoft.com/downloads/release.asp?ReleaseID=18924 File system.1st in the root directory a copy of the registry exactly as it was when Win95 was first installed. To copy it attrib -h -s -r system.1st Copy it to the Windows directory (copy c:\system.1st c:\windows) attrib -h -s -r system.dat and then delete it rename the copy of system.1st as system.dat and reset attributes as attrib +h +s +r system.dat Back up registry files, system.dat and user.dat. You cannot use Explorer or DOS to copy these files. Use cfgback.exe on W95CD\other\misc\cfgback folder. Copy cfgback.exe to c:\windows and then copy cfgback.hlp to c:\windows\help. To make a backup double click cfgback.exe and follow instructions. Registry editing. A Registry entry is called a key. Back up system.dao, system.dat, user.dao and user.dat. Choose Start, Run, type regedit.exe in the Open box. Press Ctrl and F, and in the 'Find what' box, type in the name of the errant driver, without the .vxd extension. Now make sure only Keys is checked in the 'Look at' section, and click Find next. You should land on a folder under hkey_local_machine\system\currentcontrolset\services\vxd. Triple check that you have highlighted the correct Registry key before pressing the Del button and exit the Registry Editor. Each time Windows starts it creates a backup copy of the registry, system.da0 and user.da0. To restore them get to the command prompt in safe mode, then type cd\windows attrib -s -h -r *.da? ren system.dat system.tmp copy system.da0 system.dat ren user.dat user.tmp copy user.da0 user.dat Then restart the computer. Windows 98 does not create .dat files as it uses a different system for creating Registry backups. The W98 registry checker keeps several backups in the hidden SysBckup folder (in the Windows folder). These are named rb000.cab, rb001.cab etc. When the registry checker adds a new backup it deletes the oldest. Restore registry in W98, run c:\windows\scanreg.exe/restore Internet sites visited - hkey_user/software/microsoft/internetexplorer/typedurls Disconnected IDE often a cause of missing CD drive - hkey_local_machine\system\current controlset\services\VxD\IOS. If it contains an entry NoIDE, then delete and reboot. The machine will redetect the IDE channel. Some viruses will also hide the CD. Registry entry for CD drive letter Hkey_local_machine/software/microsoft/windows/current version/setup Double click source path. To optimise the registry: First run Regclean. For W95 make a batch file containing regedit /e temp.reg regedit /c temp.reg Store as smallreg.bat and run in DOS. Can take a long time. W98 start in DOS and type scanreg /opt. ©IPK30/04/17 WME Create startup disk. Restart using disk. Select minimal boot. At DOS prompt type scanreg /opt Win XP To back up the Registry run Regedit and then File, Export and give the Registry backup a name. Removing trojan etc:Hkey_Classes_Root\exefile\shell\open\command Hkey_Local_Machine\Software\classes\exefile\shell\open\command. Both of these keys should only contain the entry"%1" %* Other keys to check:Hkey_Local_Machine\Software\Microsoft\Windows\CurrentVersion\RunServices\ Hkey_Local_Machine\Software\Microsoft\Windows\CurrentVersion\Run\ Hkey_Local_Machine\Software\Microsoft\Active Setup\Installed Components\KeyName\ Hkey_Classes_Root\.dl Remove all references to trojans etc. Also check win.ini files and system.ini files. In win.ini look under RUN= and system .ini shell= in the [boot] section, which should just contain the line explorer.exe if anything. (Start Run Sysedit ) Check for Run and Run Once:HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run and RunOnce -Repeater A device used to extend transmission distances by restoring signals to their original size and shape. Typically used within Ethernet networks to extend segment lengths. Repeaters function at the physical layer in the OSI model. -Resilience Ensuring that there are no single points of failure. Often done by using multiple servers, firewalls, switches etc so that there is always backup in case of problems -Resource monitor: Monitors System, User and GDI. These memory areas are only used by 16 bit software. Resources for 32 bit software not restricted. -RFID Radio Frequency IDentification Thin Coax. Cheapernet. RG58A/U and RG58C/U. 50 ohms 2 ohms. Minimum propagation rate of 0.65c. and minimum shield coverage of 95%. -RG58 -RIMM Rambus Inline Memory Module. Also known as RDRAM. This memory has the potential to run at speeds of up to 800MHz as opposed to SDRAM's maximum of 133MHz. Speed is also increased by processing instructions 16 bit at a time rather than 8 bit. Any unused RIMM slots require a CRIMM (Continuity RIMM) to be installed - basically a blank that completes the circuit. -Ring A network topology in which each station is connected in series to form a closed loop. -RIP Routing Information Protocol. See OSPF. -RIP Regulation of Investigatory Powers Act 2000. Recognises that some actions which are essential to keep a network functioning may result in communications being seen by the network operator, e.g. re routing of incorrectly addressed emails. The Act makes clear that users of networks should expect such actions to take place routinely; there being no requirement on the network operator to give warning of the possible loss of privacy. ©IPK30/04/17 Organisations may also examine activity on their own networks for some business purposes. However, before this may be done, all users must be informed that their communications may be monitored. The Lawful Business Practice regulations supporting the Act set out the purposes for which monitoring may be used. These include ensuring compliance with acceptable use policies and other organisational rules, but only after users have been informed of the rules in advance. Warn staff if and when they are being monitored. Warn people e-mailing your company that e-mails may be monitored. Regularly inform staff about what is being monitored. Only monitor staff covertly with police involvement. -RIPE Réseaux IP Européens - a collaboration between European network operators using the TCP/IP suite of protocols to deliver Internet services. -Ripping The process of changing data from one form to another. Often used for changing CD music files (.cda) to .mp3 files. -RIPREP A remote installation wizard for Windows server operating systems. -RIS Remote Installation Services - part of PXE -RISC Reduced Instruction Set Computer. -RJ45 Registered Jack 8 way modular FCC connectors. Wired to schedule 258A, 10BASE-T Pin No. 1 2 3 4 5 6 7 8 Pair ID T2 R2 T3 R1 T1 R3 T4 R4 10BASE-T nc nc nc nc Colour / Tracer White / Orange Orange / White White / Green Blue / White White / Blue Green / White White / Brown Brown / White Pair 3 Pair 2 1 1 -RL 2 3 4 5 6 7 2 Pair 1 3 4 5 Pair 4 6 7 8 Socket front 8 Return Loss is the difference between the power of a transmitted signal and the power of the signal reflections caused by variations in the channel impedance. High ©IPK30/04/17 return loss values mean a close impedance match, which results in a large difference between the powers of transmitted and reflected signals -RLAN Radio Lan. Contains the HIPERLAN. Uses frequencies in the range 5.150GHz and 5.875GHz. Divided into three bands. Band A 5.150 to 5.350GHz Band B 5.470 to 5.725GHz Band C 5.725 to 5.875GHz -RLDRAM Reduced Latency DRAM -RMS Rights Management Services - MS Windows 2003 server. It allows you to encrypt documents and e-mails on your network and to have full control over who can read them and what they can do with them. Can also be applied to e-mails to stop them being forwarded -RoHS Restriction of Hazardous Substances - at the heart of the WEEE regulations. -ROI Return On Investment -ROM Read Only Memory. -Root directory Maximum number of entries is 512. Long file names take up additional entries. -Router A device used for communications between two networks. They function at the network layer (3) of the OSI model and can determine the best route to send data. In a packet switching network, such as the Internet, a router is a device which examines packets of data and sends them to their appropriate destination. Routers provide access control. They will pass on packets to a destination only if they have a rule that says that they can. They stop broadcasts across networks. Allow departments of a network to be placed on separate subnets - making management and fault finding easier. -RPC Remote Procedure Call. Methods for objects to talk to each other. It allows a program that is running on one computer to seamlessly access services on another computer. Uses ports 135, 137 and 139. -RPC-2 Regional Playback Control. Used on DVDs. Allows region information to be set up to five times before your drive is locked to the last setting. Region 0 Region 1 Region 2 Region 3 Region 4 Region 5 Region 6 Region 7 Commonly used to describe no region locking Canada, US, US Territories Europe, Japan, Middle east, South Africa South east Asia, Taiwan Australia, Caribbean, Central America, Mexico, New Zealand, Pacific Islands, South America Africa(part), India, Pakistan, Russian Federation China, Reserved ©IPK30/04/17 Region 8 Special International venues, i.e. aeroplanes, cruise ships etc Often PC DVD drives are not region protected but the MPeg2 decoder cards and software players are. -RRAS Routing and Remote Access Service. W2k VPN. Also part of Windows Server 2003 - built in network layer firewall. -RS-232/V.24 EIA interface standard between DTE and DCE, employing serial binary interchange. The industry's most common interface standard. -RS-422, RS-423 EIA interface standard that extends transmission speeds and distances beyond RS-232/V.24. RS-422 is a balanced voltage system with a high level of noise immunity, RS-423 is the unbalanced version -RS-449 EIA general purpose 37 pin and 9 pin interface for DCE and DCE, employing serial binary interchange. -RS-485 Balanced interface similar to RS-422 but using tri-state drivers for multidrop applications. -RSN Robust Security Network, a WPA replacement built on 802.1x and the Advanced Encryption Standard. -RSS Really Simple Syndication - used for exchanging content between websites. Often used to broadcast updates -RSVP ReSource reserVation Protocol - Used in VoIP. Enables the sender to request a specific level of service across the network -RTL Register transfer Level -RTP Real-time Transport Protocol Used in VoIP to ensure that data is reassembled in the correct order at the destination -RTOS Real Time Operating Systems -Ruby An interpreted scripting language for object orientated programming Part of the Rails open source framework for developing database-backed web applications. Although it is a pure object orientated language it can masquerade as a procedural one. Created in Japan by Yukihiro Matsumoto and first released in 1995. It is written entirely in C. -Run box history Stored in hkey_current_user\software\microsoft\windows\current_version\explorer\runmru -RUNDLL32.EXE -Run time systems Used for internal activation of system functions. Run time software creates an environment in which an object program can be run and debugged. Some run time systems are very similar to interpreters. ©IPK30/04/17 SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS -SAC Scientific Advisory Committee -SACD Super Audio CD. From Sony and Phillips. A one bit system with a 2.8224MHz sampling rate and a 100kHz audio bandwidth. Uses Direct Stream Digital (DSD) instead of PCM. This approach records audio signals at a high sampling rate and then converts them into 1bit digital data. The reproduction of an analogue waveform is extremely accurate. It also eliminates aliasing filters and decimation digital filters in the recording studio as well as interpolation digital filters in playback. SACD is a two channel product but multi-channel is planned. Also see DVD-Audio -Safe Mode Hold down CTRL when W98 boots to get Start up menu. Then select Safe Mode. -Sale of Goods Act 1979 Goods must be fit for purpose and should be expected to last a reasonable life time -SALT Speech Application Language Tags -Samba An application used on Unix and Linux systems to enable SMB, so allowing the Unix and Linux machines to appear on a Windows network so that file sharing can take place. -SAML Security Assertion Markup Language. -SAN Storage Area Network. A collection of storage and networking components that are dedicated and optimised to the task of attaching storage devices to servers in a way that allows them to be shared. Fibre channel used for the high speed connection. The command set protocol on a SAN is primarily Fibre Channel SCSI (FC-SCSI) as defined by the Fibre Channel standard. The server sees a SAN-attached device as a directly attached SCSI device, though the SAN could be anywhere on the dedicated fibre channel. A major implementation difference between SANs and other networks is that the usual one to one correspondence between a logical server and a physical box disappears. -Sarbanes-Oxley Corporate governance regulations introduced by the US government. It sets out the requirements for company auditing. -SAS Serial Attached SCSI. Successor to parallel SCSI. Initial data rates for SAS will be 3Gb/s and at least 300Mb/s. -SATA Serial ATA. Speeds 150 - 300MB/s. Uses a cable with 7 wires. Uses the data itself as the clock to avoid phase delays as found with Ultra ATA. Has a clock speed of 1500MHz, so giving a bandwidth of 150MB/s -SAX object orientated programs. The simple API for XML - a standard interface to XML parsers from ©IPK30/04/17 -Scanner Use either CCDs (Charge Coupled Devices) or CIS (Contact Image Sensor) technology. CCDs better and more common. The light source is usually a cold cathode lamp (unlike a fluorescent tube it has no filament, generates little heat and provides a more consistent white light). Colour separation is achieved through a lens that splits the incoming light into three channels; red, green and blue. These then pass through a colour filter onto a discrete section of the CCD. The scanner combines all the data to form a single, full colour image. The CCD records the lightness of the reflected or transmitted light as an intensity. When the scanner scans an image, the lamp illuminates a thin strip of the image called a raster line. The reflected or transmitted light is captured by the CCD array. In a 1200dpi scanner, where the scanning width is 216mm (8.5"), there are 10,200 (8.5 x 1200) usable CCD elements in the array. As the array is much smaller than 8.5", an optical system focuses the light from the raster line down to the appropriate size of the CCD array. original scanner platter white cold-cathode lamp colour filter and CCD precision optics mirrors scanning carriage The smallest distance that the scanning carriage can move determines the vertical resolution. CIS systems use a tightly packed array of red, green and blue LEDs. The optical system of a CCD scanner are replaced with a single row of sensors mounted close to the source image. CIS scanners can be much thinner than CCD scanners. -SC connector Used for optical fibre. Features a moulded body and a push-pull locking system. To terminate a fibre, put strain relief sleeve onto fibre and then strip fibre to the 125µm coating using the Miller strippers. Check that the 250µm layer is removed by trying to insert it into a connector! Inject a connector with glue from a syringe until excess comes through the end of the connector. Wipe off the excess. Dip the stripped fibre into the accelerator and insert into the connector (quickly!) and leave to set (30s). When set scribe fibre where it emerges from connector with sapphire scribe (0.1mm). Break excess into the sharp box. Examine with microscope to check that it is a clean cleave. Then start polishing with 12m film (grey?). Burnish - ensure that the paper stays on the connector or it could damage the fibre. Then onto 5m film (yellow), then finally 0.3m film (white) on base and using the terminator in the polishing puck on the plastic surface. Use figure of eight motion. Wash with isopropyl alcohol. Examine with microscope. Repeat until core crystal clear. Put on outer casing and push in using screwdriver from the rear, taking care not to slip and break fibre. Push on strain relief boot. -SCE -Schema System Configuration Editor. For W98 run msconfig.exe In the context of Windows Server operating systems, a description of the classes and their necessary attributes stored within Active Directory. ©IPK30/04/17 -SCMS Serial Copy Management System. Used on Digital Audio tapes to prevent copying. -SCSI Small Computer System Interface. Ultra3 SCSI introduces 160MB/s data transfers through the use of double transition clocking (the data signals are clocked into the receiver on the leading and trailing edge of the REQ or ACK signal. In Ultra2 SCSI, the REQ and ACK clocks ran at 20MHz. In Ultra3 SCSI, both the data and clock lines now operate at 40MHz SCSI 1 5MB 50 pin 8-bit bus SCSI 2 10MB 50 pin 8-bit bus Wide SCSI 20MB 68 pin 16-bit bus Ultra SCSI 20MB 50 pin 16-bit bus Ultra wide SCSI 40MB 68 pin 32-bit bus Also known as SCSI-3 Ultra 2 SCSI 80MB 68 pin. Ultra 160 SCSI 160MBps. 16 bit bus but transfers data on both the rising and falling edges of the clock signal Hard drives are the only devices to use Ultra 2 SCSI. -SD Secure Digital memory cards - contain a manual write protection switch. -SDH Synchronous Digital Hierarchy. See SONET. Used in Europe -SDI Single Document Interface. Used by Office 2000. See MDI -SDLC Synchronous Data Link Control. IBM standard protocol -SDM System Definition Model - part of XML -SDP Session Description Protocol - generally used with SIP to describe the attributes of a SIP session. Although described as a protocol, it is more of a format for describing multimedia sessions -SDP Service Discovery Protocol. Used on Bluetooth -SDR Software Defined Radio. SDR moves large parts of the analogue circuits in radios into software which makes the radio programmable, and so can be easily updated to cope with new types of signals. -SDRAM Synchronous Dynamic Random Access Memory. A type of memory that synchronises itself with the speed of the CPU bus. About twice as fast as EDO ram A number starting with PC66 indicates 66MHz bus and PC100 indicates 100MHz bus. If individual memory chips have -10 or -8 suffix usually indicates the operating time in ns. Uses a synchronous interface with all inputs referenced to the rising edge of the clock allowing all of the address, control and data input buffers to be identical. DDR SDRAM data is driven relative to both edges of the clock, thus in effect doubling the data speed of memory. PC266 (using a clock frequency of 133MHz), with the input and output data changing every 3.75ns ©IPK30/04/17 -SDSL Synchronous Digital Subscriber Line. Offers data rates of up to 3Mbps in both directions. SDSL is an umbrella term for a number of supplier specific implementations over a single copper pair providing variable rates over a symmetrical service. It uses 2B1Q HDSL run on a single pair with an Ethernet interface to the customer. It is likely that this will move quickly towards the higher performance standard G.SHDSL. -Search Engine Used to find Internet sites. e.g. www.google.com. Once a search engine knows about a site it will index it. This involves sending one or more automated agents, or 'spiders' to work their way through the site following the links. To stop a spider from indexing certain pages, create a file called ROBOTS.TXT and place it in the root directory of the site. The format of the file is as follows: User-agent: * Disallow: /scripts/ Disallow: /news/ The first line specifies which search engines to exclude: an asterisk is a wildcard, meaning that all search engines should obey the following rules, a list of directories that the engines should ignore. Individual pages can be specified as in Disallow: /backend/admin/logon.php Comments can also be added by preceding them with a # character e.g. Disallow: /news/ # No point in indexing these. Search engines are only interested in text and not pictures. Meta tags are rarely used. Search engines mainly interested in the main content and the title in particular. Search engine and ranking rules - see http://searchenginewatch.com -SECC Single Edge Contact Cartridge. Used by Pentium II processors. Fitted into a Slot 1 socket -SEM Security Event Management -Serial ATA Replacement for parallel buses which suffer from cross talk, signal ringing and cross talk. Needs only four wires to transfer data at 150MB/s as opposed to the parallel ATA which transfers data at 133MB/s. -Serial port 8250, 9600bps 16450 19200bps 16550A 115200bps 16650 230.4kbps 16750 921.6kbps Serial Ports. COM1 IRQ4 3F8 COM2 IRQ3 2F8 COM3 IRQ4 3E8 COM4 IRQ3 2E8 COM5 IRQ4 3E0 COM6 IRQ3 2E0 COM7 IRQ4 338 COM8 IRQ3 238 Null Modem Serial Cable. RXD - TXD ©IPK30/04/17 TXD - RXD RTS - CTS CTS - RTS GND - GND 9 pin to 9 pin. 2-3, 3-2, 5-5. 9 pin to 25 pin. 2-2, 3-3 and 7 (9 pin) to 5 (25 pin). 9 pin serial plug. Looking at the base of a female plug. 5 4 3 2 1 9 8 7 6 25 pin serial plug Pin 1 Data Carrier Detect DCD Pin 8 Pin 2 Data in RXD Pin 3 Pin 3 Data out TXD Pin 2 Pin 4 Data terminal ready DTR Pin 20 Pin 5 Ground Pin 7 Pin 6 Data set ready DSR Pin 6 Pin 7 Request to send RTS Pin 4 Pin 8 Clear to send CTS Pin 5 Pin 9 Ring Indicator Pin 22 Data terminal Equipment (DTE) e.g. a microcomputer - fitted with a male connector. Data terminating equipment (DCE) e.g. a MODEM - fitted with a female connector. I/O lines usable on an RS232 port. Outputs, RTS, DTR Inputs, DCD, DSR, CTS, RI Some PC manufacturers use TTL levels instead of the +12/15V. TXD can be used to gain a small amount of power for a control circuit. Set Break (bit 6, base + 3) enables the TXD line to be made high permanently. COM1 base address usually 2F8 and COM2 is usually 3F8 Address base+3 bit0 WLS0 bit1 WLS1 base+4 base+6 DTR RTS Delta Delta CTS DSR Elektor November 1996 bit2 STB bit3 PEN bit4 EPS bit6 Set break 0 RI bit7 DLAB loop CTS bit5 Stick parity 0 DSR Out1 Trailing edge RI out2 Delta DCD COM1 3F8 3F9 3FA 3FB 3FC 3FD 3FE COM2 2F8 2F9 2FA 2FB 2FC 2FD 2FE COM3 3E8 3E9 3EA 3EB 3EC 3ED 3EE COM4 2E8 2E9 2EA 2EB 2EC 2ED 2EE 0 DCD Serial port addresses and locations of I/O memory. Transmit/Receive Buffer Interrupt enable register Interrupt identification register Line control register(+3) Modem control register Line status register Modem status register Elektor March 2000 base +1 +2 +3 +4 +5 +6 ©IPK30/04/17 -SET Secure Electronic Transaction. Developed by Mastercard and VISA. Devised in 1996 but because proprietary software needed it has not made a big impact. Public key technology is implemented to support authentication of all parties and encryption of all sensitive transaction data. -SFC System File Checker. Used to restore Windows 9X (not ME) from Windows CAB files. W98 Start - Run - SFC -SFTP Shielded Foil Twisted Pair cables. -SGML Standard Generalised Mark up Language. HTML is a simplified form of this. Has been the defacto method of expressing data in text processing apps for high end document publishers since 1986. -Shadow Mask Thin metal sheet of metal with thousands of tiny holes punched in it. These holes are lined up with the corresponding screen pixels to ensure that the correct beam hits the intended red, blue or green phosphors. Not as bright as Aperture Grille CRTs. -Shannon Limit The maximum amount that data can be compressed. Named after Dr Claude Shannon the author of a 1948 treatise on communications technology. Worked for the Bell labs during and after the war. Also invented the word Bit. Shannon's Law defines the theoretical maximum rate at which error-free digits can be transmitted over a bandwidth limited channel in the presence of noise. Usually expressed in the form C = Wlog2(1+S/N), where C is the channel capacity in bits per second, W is the bandwidth in Hertz and S/N is the signal to noise ratio.(?). Discovered that I = log2N where I is the number of bits of information in a message and N is the number of different possible messages. -Share An object on WinNT that has been made available for network access. -SHDSL Symmetric High bit rate DSL -Shift * delete End F4 Home inserting CD Deletes an item without it going to the recycle bin. Select to end of line Repeats the last search, bypassing the dialog box. Select to beginning of line Select character to the right Select character to the left Bypass autoplay -Short Code First programming computer language - developed in 1949. Had to be hand coded into binary until Grace Hopper, working for the US navy wrote the first compiler in 1951. -SHS -SIEVE Microsoft scrap file format. Can hold anything. A multi-vendor scripting language that provides a universal way for users to create filters for e-mails. ©IPK30/04/17 -SIG Special Interest Group -Signature Specific strings of binary code in most viruses (except polymorphic) that allows anti-virus software to detect them. -SIMD Single Instruction Multiple Data. Also known as SSE -SIMM Single Inline Memory Module - small circuit boards which hold a row of memory chips. 72 pin connector, and uses a 32 bit wide bus. As Pentium processors have a 64 bit bus, SIMMs must be installed in pairs. -SIMPLE -SIP SIP for Instant Messaging and Prescence Leveraging Extensions Sessional Initiation Protocol. A protocol for initiating multimedia in the application layer. Supports name mapping and redirection services, users can initiate and receive communications from any location. It works on a request/response basis, and participants are identified by URLs. Requests can be sent through any transport protocol, such as UDP, SCTP, and TCP. SIP determines the end system to be used for he session, the communication media and media parameters. Once confirmed, SIP establishes call parameters at either end of the communication, and handles call transfer and termination. VoIP is poised to start replacing this network by running everything over the data network. The potential cost savings make this a very attractive proposal, but there are still problems - the data network was never designed to handle complex communications sessions. In VoIP, none of the signalling protocols required are present, unlike in a PSTN system, and a user may be constantly switching IP address, either by physically transferring his or her location or because of the expiry of DHCP leases. This immediately makes it more complex to make connections. SIP is an IETF standard designed to provide advanced telephony services over the internet. As the name suggests, it is used to establish, terminate and modify communications sessions in an IP network. It began life as a component of the multicast backbone (Mbone) network. This was an experimental network designed to deliver multimedia content over the network. SIP is not a standalone protocol and doesn't actually understand what a session is. Instead it interoperates with existing protocols and just swaps Meta data that enables session initialisation. A session can be as simple as a two-way telephone call, but can also be a fully-blown multimedia conference call. As SIP only provides the method for dealing with sessions, it has to work alongside other protocols and standards, which provide the level of service required by real-time communication. Typically, communications require a guaranteed delivery time, which can be provided by the real-time transport protocol (RTP). Voice quality has to be guaranteed using protocols such as RSVP and YESSIR. Directory integration with LDAP is essential for user discovery, while authentication server support, such as RADIUS, ensures that users are correctly identified. To facilitate proper communication, SIP has to provide a range of features and functions to establish a session. User Location. SIP has to provide the function that locates where a user is currently located. It is common for a user to have a PC at work and home, a laptop and even a VoIP phone. An incoming connection might require that all devices ring at the same time, that one device gets preference or that a round-robin ring around takes place. SIP has to deal with this dynamic configuration information and correctly locate the user. ©IPK30/04/17 Call Initialisation. Once a user has been located, a session has to be established. Although SIP doesn't understand the session, it has to transmit the description of the session from the caller to the receiver. This usually results in negotiation between all of the parties involved in the call. It could be that a device doesn't support video, but only voice. SIP transfers this information using the multipurpose internet mail extensions (MIME). This is used in web and email services to describe content. This means there is always a wide-range of options available in negotiation. The most common form of session description used by SIP is the Session Description Protocol (SDP). Call modification. Once a call is established, SIP still has a role to play. A call in progress can change features, such as a video stream being added to a voice conversation. New parties can also be added into a conversation, which requires additional negotiation of features. Call modification doesn't have to be as drastic as either of these measures. Common telephony functions, including muting and call holding, are also supported by SIP. The range of call features supported depends on the session description protocol in use. Call TerminationAfter. When all users are finished with the session they hang-up. SIP has to deal with this call termination. Client/server architecture of SIP. The User Agent Client (UAC) sits on the client and is responsible for making any SIP requests to other clients. The UAC is also the component that accepts and deals with any request that comes in, including call initialisation, modification and termination. User Agent Server. There are three types of user agent server (UAS): stateful proxy server, stateless proxy server and the re-direct server. Proxy servers receive request and work out where to send them. This is generally onto the next server until the destination is located. A stateful proxy server retains information of all requests and responses. This can be used to send a request to multiple destinations and only pass on the best response. A stateless proxy server simply passes requests on but doesn't retain any information. A re-direct server doesn't proxy requests, but returns the destination address to the caller. The caller can then make a request directly to the destination. To see how this works consider a simple example of user 'A' trying to call user 'B'. A's UAC sends a SIP invite request to its local UAS. If this is a proxy server, then it forwards the request to the next UAS until it hits its destination. If it is a re-direct server then it returns the direct address of B. In SIP, addresses are represented as URLs and follow a similar layout to email addresses. The invite includes a full description of the session including all of the media streams that A wants to use. B replies to the invitation, but includes a description of any modifications that he wants to make. This is for compatibility reasons, as B might support all of the features that A asked for. After this negotiation is completed, the session is created and A and B can communicate. At the end of the call, either side can send a disconnect, terminating the session. All of this process is automatic. For example, when A calls B, if B picks up his VoIP videophone, the phone automatically handles the media negotiation process. When B puts the phone down, the disconnect is automatically sent. It is also the job of a SIP device to register its current location with a UAS. This ensures that a user can be found even when mobile. In the simple example above, only a single connection was covered. However, SIP can use a process called 'forking', which sends out invites to multiple devices at once. The first device to respond gets the connection. This is similar in conception to a phone pool in a helpdesk, where all incoming calls ring all available phones. However, this feature is only available if a stateful proxy server is used, as it needs to remember which connections to allow and which to block. SIP can return different media types. If a client connects to a company, then they could return a list of phone numbers for the building. It means that information can be dynamically created and transferred. SIP has well-defined messages that are used for communication. A message can either be a request or a response message. ©IPK30/04/17 INVITE is used to initiate a call and is also used to change call parameters once a session has been established. This can be thought of as a re-INVITE. ACK is an acknowledgement and confirms response to an invite. BYE terminates a call in progress. CANCEL Terminates the invite and stops all searches and devices that are ringing. OPTIONS Used to query the capabilities of a device. REGISTER Registers a device's location with a server. INFO Sends information during a session but does not modify the session state. Response messages contain numerical responses and are similar to those used by HTTP: 1xx provisional, searching, ringing, queuing 2xx success 3xx redirection, forwarding 4xx request failure (client) 5xx server failures 6xx global failure (busy, refusal, not available anywhere. 100 Continue 180 Ringing 200 OK 301 Moved permanently 302 Moved temporarily 400 Bad request 408 Request time-out 480 Unavailable 600 Busy 603 Decline 604 Does not exist SIP Message architecture. Both request and response SIP messages are built from the same three components: Start Lines. The Start Line is the beginning of every SIP message. It is first used to identify the type of message and the protocol. Depending on the message type the Start Line is either a Requestline for requests or a Status-line for responses. A Request-line includes a Request URL, which is used to identify the requested user. This line can be rewritten by proxies, although the 'To' field later on cannot. A Status-line holds the numeric Status-code and the text version. SIP headers contain a list of fields that are used to identify message attributes. The syntax is:<field>:<value> The body conveys the mechanics of a connection. It is common for the body to hold protocol information such as SDP, and only the receiving client can understand what the body means. -skins visualisation effects that customise the appearance of programs. e.g. Media Player, Winamp etc. -SLA Service Level Agreement. Defines the level of network services provision expected. -SLIP/PPP Serial Line Interface Protocol/Point to Point Protocol. These are both standards for connecting directly to the Internet, as opposed to having to log on to it via a host computer. ©IPK30/04/17 -Slot 1 Used by Pentium II and early PIIIs -Slot A AMD Athalon slot socket. Same size as Slot 1 but the processor fitted in the other way round -SLR Scalable Linear Recording. Tandberg format for back-up tapes. It is a revised version of the quarter inch tape (QIC) format and currently stores 25GB per cartridge with a data transfer rate of 2MB/s. Cheaper than DLT and has a mean time between failure of 300,000 hours. -SLR Source Level Routing - an IP routing technique that allows the originator of an IP datagram to specify the precise route that delivery should take. -SMA Shared Memory Architecture -SMART Self Monitoring, Analysis and Reporting Technology. A series of diagnostics built into a hard drive that continually checks to make sure the drive is functioning correctly. By monitoring the drive it is possible to pick up on any fatal data errors before they happen. -Smart Media Memory card. Contains no on board memory. -SMB Server Message Block - used by Windows servers. Also referred to as CIFS (Common Internet File System). The protocol is used to allow applications to read and write files or request services from remote machines. Developed by Microsoft and runs on top of other network protocols such as TCP/IP, IPX or NetBeui. SMB is the protocol used for network file sharing in Windows and DOS. NetBios protocol is based on SMB. -SME Small, Medium Enterprise -SMIL Synchronised Multimedia Integration Language. Part of XML. Provides a platform for Web based multimedia applications. First introduced in 1998 -SML Service Modelling Language - defines the way IT resources are described in XML -SMP Symmetric multiprocessing. Uses a second processor when the first is busy. -SMS Short Message Service. -SMS System Management Server (Microsoft) -SMTP Simple Mail Transfer Protocol. The Internet standard for mail delivery. The TCP/IP protocol for electronic mail. Uses TCP port 25. Has limited queuing facilities and so is used with POP3 or IMAP4 servers for client message retrieval. Uses plain text messages to transmit the data ©IPK30/04/17 Telnet to an e-mail server and type HELP - should give a list of commands. Can be used to fake e-mail addresses by typing the wrong e-mail address into the 'FROM' field. When an e-mail address is scanned e.g. user@domain, the sending station drops the user component and uses a DNS server to look up the mail record part of the domain name. The transmitter then opens an SMTP connection to the mail server and transmits the e-mail. -SNMP Simple Network Management Protocol. -SNTP Simple Network Time Protocol -SOA Service Orientated Architecture - a way of organising data and applications that enables output to be delivered in services that are meaningful to business. This requires the description of the business function to be separated from the content and process. By wrapping data and process in a layer, and publishing it as a service in a standard format, a service can be called up on demand by other services. -SOAP Simple Object Access Protocol. Closely related to XML, this is a protocol specification for invoking methods in servers, services, components and objects. Underpins MS .NET -Socket Alternative name for Port on an IP network -Socket 7 Used by Pentium, Cyrix 6x86, MMX, 6x86MX and K6. Usually ZIF. -Socket 8 Used by Pentium Pro -Socket 370 370 pins. Modern ones accept either Celeron or PIII processors. Accepts processors in the PPGA format -SOHO Small Office, Home Office. -SONET OC-192 Synchronous Optical Network. Known in Europe as SDH. This is a standard from the 1980s for metropolitan fibre rings used in ILECs. Traffic is carried in an electronic packet transported over fibre, using dual counter-rotating rings. The systems are relatively inexpensive to implement, but they were designed in the 1970s for primarily circuit switched voice traffic so they make very inefficient use of bandwidth in carrying traffic that is mostly IP-encapsulated data. -Sound Cards. 8-bit samples give about 48dB of dynamic range while 16 bit gives about 96dB. Wavetable synthesis: the sounds of genuine instruments have been recorded and digitised. Uses very short samples. FM synthesis: the sound of instruments are simulated based on a mathematical algorithm rather than actual recorded sounds. Developed over 20 years ago, creates sounds by modulating a simple pure tone carrier wave with a second waveform. This produces a third complex waveform from which it is possible to produce instrument type sounds. The most common synth chip is the Yamaha OPL-3, gives 20 simultaneous stereo voices. ©IPK30/04/17 You can create a WAV file in Sound Recorder. To produce from a CD, put CD in drive and select Start, Programs, Accessories, Multimedia, Sound Recorder. Once the program is up, start playing the CD. To adjust the sound, select Start, Settings, Control Panel, and double click the multimedia option. The Audio tab contains options for altering the recording. Settings and functions. IRQ = 05 DMA = 01 and 05 I/0 = 0220 - 022F 0330 - 0331 0388 - 038B 0220 0221 0222 0223 0224 mixer register 0225 mixer data 0226 dsp reset port 0227 0228 0229 022A dsp read port 022B 022C dsp write port (command/data), dsp write-buffer status (bit 7) 022D (dsp timer interrupt clear) 022E dsp read-buffer status (bit 7), dsp interrupt acknowledge (8-bit?) 022F dsp 16-bit interrupt acknowledge 0330 0331 -Source code The original code written in either a high level or a low level language. -Space Absence of signal, in telegraph communciations, a space represents the open condition or no current flowing. A "0" -SPD Serial presence Detect. - Memory timings. -SPID Service Profile Identifier. A number that identifies terminal equipment attached to an ISDN line. -SPIT Spam Over Internet Telephony -SPOT Smart Personal Objects Technology. - Backed by Microsoft. -Spyware Programsinstalled by advertising companies on your computer when you use the Internet. Includes:- VX2/a, SurfPlayer, DownloadPlus 1.0.6, Search-Explorer, Weathercast, FileFreedom, FirstLook, ezCyberSearch, Mass Instant Messenger 1.7, OnFlow, -Sprint First U.S. mobile operator to launch 3G service ©IPK30/04/17 -SQL Structured Query Language. A standard language for talking to databases -SRM Storage Resource Management -SSE See SIMD -SSH Secure Shell - an internet encryption system -SSI Shared source Initiative -SSID Service Set Identifier - a 32 character unique identifier attached to the header of packets sent over a wireless LAN. Sent as unencrypted text and is vulnerable to being sniffed by third parties. -STA Spanning Tree Algorithm (IEEE802.1D) designed to prevent flooding in bridged networks. -steplocking Steplocking is a technology used in high-availability servers, where each CPU runs the same task, ensuring that each one has carried out the function and that the outcome is the same. If there are differences, the system sees which of the CPUs is right, and the 'faulty' CPU is either disregarded or taken offline, with the remaining CPUs taking over. Every 'step' taken is 'locked' into place once checked. State is always maintained and high availability is provided. The more CPUs there are the better the steplocking. -STP Spanning Tree Protocol. See above. -SSL Secure Sockets Layer. Developed by Netscape and has become the internet standard protocol for providing a secure communications channel for session based encryption and authentication. Supported by all of the popular netbrowsers. The protocol runs on port 443. An SSL handshake involves the server responding to a client request by sending its digital certificate and cypher preferences. The client generates a master key, encrypts it with the server public key and transmits the encrypted master key back to the server. The server recovers the master key, returns a message authenticated with it to the client by way of authenticating itself and then all subsequent data exchange is encrypted and authenticated with keys derived from the master. SSL is application independent and can operate with http, ftp, or telnet. SSL based systems do not identify client to server unless this is specified as an option and even then only when certificates are distributed to all users. At the end of the session the keys are disposed of. -Star A network topology where the central control point is connected individually to all stations. -Stateful Inspection A type of firewall engine that works in the network layer. More secure that packet filtering firewalls which just check the header of the incoming packet. Stateful Inspection engines can look inside packets up to the Application layer. -ST connector ferrule. Used for optical fibre. Uses a bayonet locking system. Has a ceramic ©IPK30/04/17 -Stealth Virus Uses tricks to conceal itself from anti-virus software. Mainly affect DOS not windows applications -Stenography Greek words meaning Covered Writing. Hiding messages as in pictures and digitally watermarking media to avoid copyright theft. Hides one piece of information in the background noise of another, e.g. a word document inside a Jpeg file. -STP Shielded Twisted Pair cable. -STP Spanning Tree Protocol. -STR Sequential Transfer Rate. The speed at which a hard disk can read data from sequential tracks and cylinders on the platters. -Streaking This is when the printer misaligns the lines of print, leaving out a small amount of the page, which shows through as a thin white line. -Structured wiring A term applied to a cabling system implemented within a building as a pre-planned utility. -Subnets (Also see IP addresses). Allow a network class to be split up for internal use only. To the outside world they still look like a normal network. The subnet part of the address is used to define how many bits to use as the network address and how many to use for the host address. An example of a class C network is shown below. Network Address 11111111 11111111 11111111 Subnet 11 Host 000000 The subnet address means that we can have four subnets 00, 01, 10, 11. This is using classless inter-domain routing (CIDR) subnetting. In classic subnetting, 0 and 1 are reserved, which reduces the number of available subnets and also host addresses. In this example, the six bit host address means that each subnet can have 62 hosts on it. The important part of this is the subnet mask, which allows us to determine the subnet a host belongs to. Only hosts on the same subnet can talk directly to each other. Subnet masks are also 32 bit numbers that follow the IP dotted -quad notation. To work out which bits are 1s and which are 0s:- all bits in the network address portion are 1s, followed by making all the bits in the subnet mask 1s, while all the bits in the host address are 0s. So for the class C example the subnet mask is 11111111 11111111 11111111 11000000 which gives 255.255.255.192 To see how this is used take two IP addresses 192.168.72.10 and 192.168.72.14 To see if they sit on the same network we perform a Boolean AND on each address with the subnet mask. So 192.168.72.10 AND 255.255.255.192 equals 192.168.72.0 also 192.168.72.14 AND 255.255.255.192 equals 192.168.72.0 Since both calculations give the same network address, 192.168.72.0 we know that the hosts are on the same subnet and are allowed to talk. If the second IP address was 192.168.72.240 an AND with 255.255.255.192 would give 192.168.72.192 Since this differs from the 192.168.72.0 the addresses must reside on different subnets. ©IPK30/04/17 The subnet mask will differ depending on the class of the network, but class C networks will always have a subnet mask that starts 255.255.255 A subnet mask of255.255.255.0 means that all hosts on the network can talk to each other. Other valid subnet masks on a class C network are given below. Subnet mask 255.255.255.128 255.255.255.192 255.255.255.224 255.255.255.240 255.255.255.248 255.255.255.252 Number of subnets 2 4 8 16 32 64 Hosts on each subnet 126 62 30 14 6 2 In the example the range of addresses would be: Subnet 1 2 3 4 Range of addresses 192.168.72.1 - 62 192.168.72.64 - 126 192.168.72.128 - 190 192.168.72.193 - 254 The missing addresses are used for the network address and the broadcast address. So the first subnet has a network address of 192.1168.72.0 and a broadcast address of 192.168.72.63 while the last has a network address of 192.168.72.192 and a broadcast address of 192.168.72.255 For subnetting to work, routers have to be updated, adding entries of the type (this-network, subnet,0) and (this-network, this-subnet, host). This allows a router to route between subnets. -STX Start of Text. A control character used to indicate the beginning of a message. It immediately follows the header in transmission blocks. -Summer Time In the UK the clocks go back at 3am on the last Sunday in October and go forward at 2am on the last Sunday in March. -SUS Software Update Services - Microsoft. Provides the latest patches. -SVCD Super Video CD. Supported by lots of DVD players. Developed in China as a follow on from VCD (video CD). It is not as high quality as DVD video but is better than VCD -SVG Structured Vector Graphics - XML based language for displaying vector graphics. Scalable Vector Graphics. -SWAP Shared Wireless Access Protocol -Swap file Also known as virtual memory, this is a portion of the hard disk set aside for Windows to use as a cache, basically to speed up transfers to and from disk. -SWF format. Used in Flash Shockwave for Flash file format a web optimised, vector based ©IPK30/04/17 -Switch An intelligent hub that reads the destination addresses of incoming data packets and only sends them to the port where the recipient is physically attached. Switches used to form VLANs. Can support two kinds of VLAN membership - Port or MAC address. Layer 3 switches have routing capabilities and so can be used for the core of a VLAN network. As packets arrive, the switch can make the decision on whether to route or switch a packet. -Switching The process by which data packets are received, stored and transmitted to the appropriate destination port. -Sybase A relational Database Management system. Invented at the university of California Berkeley. A deal with Microsoft led to Sybase code being used for SQL server. When the deal broke up, Sybase SQL Server was renamed Adaptive Server and Microsoft re-engineered and re-wrote the code. -Symbian A consortium of companies (Psion, Phillips, Nokia, Matsushita) that has developed the EPOC operating system for mobile devices including phones. -Synchronous transmission Data bits are sent at a fixed rate with the transmitter and receiver exactly in time. Eliminates the need for start and stop bits. -SynchML The XML based data synchronisation protocol. -SysAD PC interface system for peripheral devices. -Sysedit System Editor. Used to edit system files in W9X (not ME). In ME use Msconfig. -System File Checker The data base for this is default.sfc -SYSTEM.INI The windows equivalent of the config.sys file. Contain the hardware details. To comment out a line place a colon at the beginning of the line. TTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTT -TAPI Telephony Application Program Interface -TCA Target channel Adapter, an adapter that connects an InfiniBand link to an I/O device such as a disc subsystem -T-Carrier See Digital Telephony -TCPA Trusted Computing Platform Alliance -TCO Total Cost of Ownership ©IPK30/04/17 -TCO & MPR Standards for monitors. Minimum refresh rate for monitors should be 75Hz -TCO99 A Health and Safety standard for monitors. -TCPA Trusted Computing Platform Alliance. Founded in 1999 by HP, Compaq, Intel, IBM and Microsoft. The goal is to employ various checks in software and hardware to detect and then enforce the conditions under which particular bits of data and code can be used. Microsoft Palladium project -TCP/IP Transmission Control Protocol / Internet Protocol originally developed by the US Department of Defense in the 1960s during the cold war. The DoD's Arpa (Advanced Research Projects Agency), now called Darpa, began a partnership with US universities and corporate researchers to design open, standard protocols and build multivendor networks. The fruit of their work was ArpaNet, the first packet switching network running the NCP (Network Control Protocol). In 1974, Vint Cerf and Robert Kahn proposed a new set of core protocols for the ArpaNet, which developed into TCP. TCP/IP is the protocol used by the Internet and many intranets and LANs. Each device is given a unique address in the format 255.255.255.255. Each of the millions of computers on the Internet must have a unique TCP/IP address in order to be correctly identified. Used to send packets across multiple networks. TCP/IP has its own reference model, which differs from the OSI reference model. It is actually two protocols - Transmission Control protocol (TCP) and Internet Protocol (IP). IP is a connectionless protocol and unreliable, while TCP is connection-orientated through a three way handshake. TCP runs over the top of IP, which runs over the top of the network protocol it is on. IP was designed to let hosts inject packets independently into the network and have them routed to their destination. Packets can even arrive in different orders. This is known as the internet layer in the reference model. The need for routing, and avoiding congestion, means the internet layer is very similar to the network layer in the OSI model. Layers 1 and 2 are replaced by the host-to-network layer, which lets IP packets drop onto heterogeneous networks. Above this is the transport layer, which allows two stations to communicate. It provides the same function as the transport layer in the OSI model. It defines two end-to-end protocols, TCP and UDP (User Datagram Protocol). TCP introduces flow control and provides reliable transmission. UDP is a connectionless, unreliable protocol for applications that don't need TCP-level reliability. UDP is often used where prompt delivery is more important than error checking, as is the case with streaming voice and video. The TCP/IP model jumps straight to the application layer. It contains all of the higher-level protocols and includes Telnet, FTP, SMTP, DNS, NNTP and HTTP. -TDD Time Division Duplex - only supports data not voice. -TDM Time Division Multiplexing. Transmitting multiple channels on a single transmission line by connecting terminals, one at a time, at regular intervals. -TDR Time Domain Reflectometry. Used to determine cable length. -Telecommunications (Lawful Business Practice) (Interception of Communications) Regulations 2000 ©IPK30/04/17 The Lawful Business Practice regulations supporting the Regulation of Investigatory Powers Act set out the purposes for which monitoring may be used. These include ensuring compliance with acceptable use policies and other organisational rules, but only after users have been informed of the rules in advance. -Telephone numbers 0845 1470 1616420845 17070 pay as you go needed when caller line ID is suppressed on your telephone. free anytime numbers. BT clear line -Telnet A terminal emulation program used for logging onto another computer, especially a large mainframe such as those containing the online catalogues of libraries. -TEN-155 Trans-European Network at 155Mb/s. A project to connect European Academic and Research networks at 155Mb/s. -Ternary DRAM Three states 0, 1, don't care -TFT Thin Film Transistor. A high quality liquid crystal display screen that uses between one and four transistors per pixel to control illumination. Each transistor requires little power and has a fast response time, so it can switch on and off very quickly. Three main types. The oldest - TN+film has relative poor viewing angles around 115° and a slow response time. IPS - In Plane Switching - improves the viewing angle to around 160°. A slightly different method is used by MVA - Multidomain Vertical Alignment - panels, where each pixel is given four areas. These areas adjust their intensity to even out the brightness when viewed from different angles. These also have viewing angles of around 160° and a faster response time. The best are the Super-IPS panels and have a viewing angle of up to 170° and an even faster response. -Thick Ethernet See 10BASE5. -Thin Ethernet See 10BASE2. -TIA Telecommunications Industries Association (of North America). -TIFF Tagged Image File Format. Used to store bit mapped images. -Tight buffer fibre outer jacket aramid yarn optical fibres ©IPK30/04/17 250m 50/62.5m 125m 900m Four core fibres have colours of blue, orange, green and brown. Eight core fibres have colours of blue, orange, green, brown, grey, white red and black. Infra red radiation used at a wavelength of 850nm. Attenuation losses for 62.5/125 fibre at 1Gbps are 3dB/km, 0.7dB/connector and 1.5dB/connector pair, 0.3dB for a fusion splice. Maximum length for 62.5/125 fibre at 1Gbps is 220m. For 50/125 fibre at 1Gbps is 550m. See SC connector for termination. -Tim Berners-Lee Credited with inventing the World Wide Web in 1989 and wrote the first Web client and server in 1990. He is a director at the W3C, the open forum for Internet technology development. He holds the 3Com founders chair at the Laboratory for Computer Science at the Massachusetts Institute of Technology (MIT). -TIP Tablet PC Input Panel -Tiresias Screen Font Font designed to avoid legibility problems. Initially devised for subtitles. www.tiresias.org -TKIP Temporal Key Integrity Protocol. Improvement upon WEP and uses a 128-bit temporal key combined with the client's MAC address -TLD Top Level Domains -TLS Transport Layer Security - a protocol that ensures privacy between communicating applications and their users over WLANs and the internet. -Token Ring A type of network where all of the computers are arranged (schematically) in a circle. A special bit pattern travels around the circle. To send a message, a computer catches the token, attaches a message to it, and then lets it continue to travel around the network. The traditional data transfer rate for token ring is 16Mbps though if duplex network cards are used this can be increased to 32Mbps. -Topology The physical layout of a network. See Network Topology. -ToS Type of Service - also known as IP Precedence - is information defined in two fields of the IP header. The first field, precedence, is used to identify and route packets. A second field, the ToS sub-field, can define the type of service requested for the traffic. Used in VoIP. -TPC Transmit Power control - enables WLAN clients to use the minimum output power necessary to transmit data signals if interference with other transmissions is encountered. See IEEE 802.11h ©IPK30/04/17 -TPM Trusted Platform Module -Training (And retraining) The process by which modems negotiate their communication speed depending upon the amount of noise on the line. -Tree A LAN topology that recognises only one route between two nodes on a network. The map resembles a tree or the letter T. -Trojan A program that looks legitimate, but performs some illicit activity when it is run. -TSR Terminate and Stay Resident. A program designed to remain easily accessible even while another application is running. It can stop running but stay in the PCs RAM. -TUPE Transfer of Undertakings (Protection of Employment). Designed to protect employees' jobs, pay and conditions, when organisations sold or outsourced parts of their business operations to other companies or contracting firms. -Turion AMD Athalon 64 second generation notebook cpu -Twain Technology Without An Interesting Name. Software driver that lets peripherals such as scanners and digital cameras be controlled from the PC and transfer their data to it. -Twisted Pair Cable The most common form of communications cabling used by telephones, computer terminals and LANs. UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU -UAC The User Agent Client - a SIP component that sits in end-user devices such as IP handsets or software applications to initiate and answer IP calls -UART The Universal Asynchronous Receiver/transmitter chip controls the transfer of data over a serial port. Modern chips include 16550 or even better 16650. Older types include 8550. -UAS The User Agent Server sits in the network device such as PBX or media gateway and handles SIP call signalling -UDDI Universal Description, Discovery and Integration. Provides a directory of Web services, which can be used to search for companies involved in Web services, or to file and find pieces of code that have been created for Web services, and which can be reused by the same or by other organisations. -UDMA Ultra DMA. The latest types of EIDE controllers that support data rates of 33MBps, 66MBps, 100MBps and 133MBps. Hence UDMA66 etc. Two different devices are supported on each UDMA channel and most mother boards have two such channels. ©IPK30/04/17 UDMA66 is only possible if an 80 wire cable is used and if all devices support UDMA66 on the same interface. Otherwise it runs at the speed of the slowest interface. -UDP User Datagram Protocol -UDRP Uniform Domain Name Dispute Resolution Policy -UKERNA The United Kingdom Education and Research Networking Association. -ULCC University of London Computing Centre. -Ultra ATA An IDE interface that transfers data at up to 133MB/s. Needs an 80 wire cable with a maximum length of 18 inches for reliable operation. The clock signal is sent with the data but this leads to phase distortion of the clock signal and so speed limitations. -Ultra SCSI A SCSI standard that transfers data at 20MB/s. -Ultra II SCSI The latest SCSI standard that transfers data at 80MB/s. -UML Unified Modelling language, the standardised language for software blue prints. -UMTS Universal Mobile Telephone Service -Uninstall Programs. Ensure nothing runs on Start Up: - Start - Run - msconfig - Enter - Startup Tab - Uncheck programs. Remove file association: - Windows Explorer - Remove association. Registry: HKEY_CLASSES_R¥\Applications. Click + then right click subkey matching program's file name. Select and delete. HKEY_CURRENT_USER\Software Find subkey of program's vendor - delete HKEY_LOCAL_MACHINE\Software key - search and delete registry for any reference Delete Program folder and shortcut. -UNIRAS Unified Incident Reporting and Alert Scheme. Founded in 1992. Role to gather information on software problems. Now part of NISCC. The UK governments CERT (Computer Emergency Response Team). -UNIX An operating system developed by AT&T Bell laboratories and used on many backbone Internet servers. Developed from Multics, a bloated, ambitious OS that ran over time and budget in the late 50s. When the plug was pulled, two engineers, Ken Thompson and Dennis Ritchie, devised their own OS, originally known as Unics. Unix is a powerful multitasking OS originally written in 11,000 lines of code (compared to 5.6 million for NT4 and an estimated 29 million for Windows 2000). Originally Bell distributed Unix at low cost and with the source code, which was therefore customisable. By 1982, with US government restrictions lifted and Bell sold off, AT&T decided to capitalise on the success of Unix and charge much money for it. Richard Stallman, who worked at MIT, set up the Free Software Foundation in 1984. During the 1980s ©IPK30/04/17 Stallman and a group of Hackers set about creating GNU and created many programs but not the kernel - later done by Linus Torvalds -Upper Memory Area The RAM between 640KB and 1024KB -UPS Uninterruptible Power Supply. A device that provides battery backup when the electrical power fails or drops to an unacceptable voltage level. Can be set to alert computers to shut down in an orderly manner when a power outage has occurred and the batteries are running out. Also provide surge suppression and may provide some voltage regulation. Standby UPS - "offline" until the mains supply fails then switches on within a few milliseconds Line interactive UPS - smooths out the mains waveform and corrects the rise and fall of the voltage. Online UPS - the inverter is continuously providing clean power from the battery and the computer equipment is never receiving power directly from the mains -URL Unique Resource Locator. The address of a page on the Web. e.g. the URL www.bbc.co.uk/sport/cricket.htm tells the browser to use HTTP protocol to find the server named www.bbc.co.uk and ask it for the page entitled cricket.htm, which is found in the sport directory. Usually consists of four parts: protocol, server (or domain), path and file name. eg.http/ www.microsoft.com/ magazine/tips/ default.htm -USB Universal Serial Bus. A host-slave system Transfer rate of 1.5Mbps. (Normal serial bus max speed of 115Kbps.) Originally conceived by Intel, Microsoft, Digital, Compaq, NEC and IBM. Can be hot swapped, the relevant driver being automatically loaded. Plug and Play, supports up to 127 devices with speeds of 12Mbps. Hot swappable. Type A sockets (flat) on PC or hub side. Will provide up to 500mA. Hubs can be nested up to 5 deep. View from bottom of socket (PCB side) Type A Type B 1 2 3 4 3 2 4 1 1 2 3 4 +5V –D +D GND Type B sockets (square) on peripheral which logs onto PC. Draws power. USB cables always wired 1:1 -USB1.1 Speeds of up to 12Mbps -USB2 Speeds of up to 480Mbps -USB OTG USB On The Go. USB Standard, Rev 2.0. Allows for mobile interconnectivity, by allowing a USB peripheral to be more than a simple peripheral. ie a DRD Dual Role Device. -user.exe -USSD One of the windows kernel files Unstructured Supplementary Service Data. (Mobile phones) Often referred to chat services. Faster than SMS. SMS uses store-and-forward functionality, USSD is ©IPK30/04/17 session orientated. When a user accesses a USSD service, a session is established and the radio connection stays open until the user, application or time-out releases it. During a call, USSD uses the FACCH (Fast Associated Control Channel) which is five times faster than the SACCH (Slow Associated Control Channel) used by SMS. -UTP Unshielded Twisted Pair cable. -UUCP Unix Copy Program - Early Internet Mail System -UWB Ultra Wideband. Promises speeds of up to 1Gb/s by transmitting data over a wide spectrum of frequency bands and at low power levels. Range <10m. UWB is defined as any radio technology having a spectrum that occupies a bandwidth greater than 20% of the centre frequency, or a bandwidth of at least 500MHz VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV -V.22 Synchronous/asynchronous data transmission, full duplex operation over 2-wire leased or dialup lines; 1200bps data rate (V.22.bis, 2400 and 1200 bps). -V.25, V.25 bis Provides for automatic calling and answering circuitry for use on dialup lines. V.25 parallel interface, V25 bis serial interface. -V.32 Synchronous/asynchronous data transmission, full duplex operation over 2-wire dialup lines; 9600bps. Trellis encoding modulation used to minimise errors. -V.32 bis Synchronous/asynchronous data transmission, full duplex operation over 2-wire dialup lines; supports data rates of 14400, 12000, 9600, 7200, 4800 bps data rates. Use training and retraining to determine the speed of transmission depending upon the amount of line noise. -V.33 Synchronous data transmission, full duplex over four wires. Uses the same signal modulation techniques as V.32 modems. -V.34 Synchronous/asynchronous data transmission, full duplex operation over 2-wire dialup lines; supports speeds up to 28.8kbps -V.35 CCITT (ITU) standard governing data transmission at 48Kbps over 60-to 108kHz group band circuits. -V.42, V.42 bis Uses two algorithms for error control and data compression. Uses MNP 1-4 and LAPM to control data errors and retransmit 'bad' data blocks Can usually provide data compression at 4:1. -V.44 Error compression system for modems. -V92 Standard for modems giving 56Kbps. -VDS Virtual Disk Storage - MS Windows 2003 ©IPK30/04/17 -VDT Visual Display Terminal. Useful BSI publications BS7179 Ergonomics of design and use of VDTs in offices BS EN 29241 Code of practice for design of VDT work environments -VDU Visual Display Unit. See VDT -VESA Video Equipment Standards Association. Responsible for the VESA Local Bus (VL-Bus) -Video connector Type VGA analogue, 15-way DIN in 9-way shell, 3-row D-type connector. Display adapters. MDA, monochrome display adapter. Each character was displayed on a 9x14 grid, giving 80 characters per line and 25 lines to the screen. CGA, colour graphics adapter. Four colour display and 8x8 grid giving a maximum resolution of 320x200 pixels. EGA, enhanced graphics adapter. Could display monochrome text in a 14x9 matrix at resolutions of 720x350 but also CGA colours at 320x200. VGA, versatile graphics adapter. 640x480 with 16 colours. SVGA 800x600 at 256 colours or even higher resolution. XGA 1200x1024 UXGA..1600x1200 8-bit 256 colours 16-bit 65536 colours 24-bit 16,700,000 colours 5 1 10 6 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Red (O) Green (O) Blue (O) Not used Digital ground Red ground Green ground Blue ground Not used Digital ground Not used Not used Horizontal sync (O) Vertical sync (O) Reserved. -Video memory SGRAM and SDRAM. 11 ©IPK30/04/17 -Virtual Machine (VM) An operating system running inside an operating system. Several virtual machines can run inside a host operating system, with each behaving as if it were running independently on its own physical hardware. All requests for hardware access are routed through the host operating system. -virtualisation Gives main frame type advantages to open systems storage infrastructure. Enables companies to replace dedicated i/o controllers with software solutions running on commodity hardware. Two types of virtualisation - in-band and asymmetric. In band software is like a receptionist - handling calls to the SAN, while asymmetric systems force you to make calls directly to extensions within the SAN but provide you with a phone directory to do so. In a virtualised system, a layer of middleware is introduced between the systems administrator and the disparate resources that make up the infrastructure: the administrator gives instructions to the middleware asking it for specific resources as and when the need arises. The middleware deals with the necessary devices, reallocating storage space, CPU power and other necessary elements under the covers. Virtualisation systems used on non-mainframe systems can be split into those dealing with storage, processing power and network resources. Virtualisation enables a system's physical resources to be shared by different tasks and so it helps achieve higher utilisation of the assets. -Viruses First PC virus, Pakistani Brain, appeared in 1986. Amjad and Basit Farooq Alvi. Used by the brothers to punish users of illegal copies of their software. Jerusalem uses Interrupt 21h. Michelangelo is a boot sector virus - on March 6th it wipes both hard and floppy drives as soon as the PC is turned on. Starship only infects files when they are copied from hard disk to floppy. It also creates a new boot partition on the hard disk to store the virus code then runs the real boot sector stored in the original partition. Polymorphic viruses are capable of changing form. Anti-CMOS virus:- clears the hard disk number and changes the floppy drive to 5.25in, 1.2Mb. AWARD_SW, Biostar, Biosstar, Award*: try upper and lower characters. Types of virus scanners. "Checksum" generate a checksum or CRC for every executable program each time the scanner is run. It then checks for changes between scans to detect viruses. -Visual Programming languages that allow all coding to be done graphically. -Visual Studio.net Visual C++ an object orientated language with advanced template features, low level platform access and an optimising compiler. Visual Basic Roots in Microsoft original version of Basic. Object orientated additions. Visual C# Microsofts competitor for Java. Aimed at distributed Web services applications. ASP.NET Formally called ASP+. ASP.NET is a successor to Active Server Pages (ASP). Started life as extensions to HTML. ASP.NET can produce compiled code and incorporate applications written in any of the other .NET languages. Jscript An interpreted, object-based scripting language that has fewer capabilities than C++. Related to Javascript. JScript is limited by its inability to read or write files and cannot be used to write standalone applications. Scripts can only run under an interpreter or host, e.g. ASP, IE, etc. ©IPK30/04/17 -Virus Win95.cih on 26th of April or sometimes any month it attempts to overwrite all of the data on the hard disk. For machines with a Flash BIOS it also attempts to overwrite that and so render the motherboard useless. -VLA Volume License Agreement -VLAN Virtual LAN. Standard IEEE802.1q VLANs let you segment network services according to users' business rather than physical location. Implemented using switches. There are two kinds of VLAN membership - Port and MAC address. Most VLANs are based on port membership - each port is given a VLAN ID - which is just a number. Switches are initially shipped with all ports having the same VLAN ID. All ports with the same ID are in the same VLAN. When a packet comes into the switch, the switch will only pass that packet onto a port with the same VLAN ID number. VLAN tags - added to Ethernet packets between VLAN switches - an extra 4 byte field. The receiving field has to strip this away before passing on the packet. -VL-Bus VESA Local Bus. Developed by Video Electronics Standards Association. Replaced by ISA bus and PCI. -VLIW -VOIP Very Long Instruction Word Voice Over Internet Protocol. VoIP is the process of sending digitised speech across an IP network. Although it refers to any speech transmitted in this way, the most common application for VoIP is IP telephony. To mirror the quality and efficiency of a circuit-switched telephone network, there are an array of processes that VoIP has to address. These include call setup and termination, compression and encoding, transportation, and management of bandwidth. Underpinning all of these is the design of the network used to transmit VoIP traffic and provide QoS. To begin a VoIP session, a call has to be set up between two end points, simulating the process of connecting and disconnecting two telephone handsets. This process uses one of two major protocols - H.323 or Session Initiation Protocol (SIP), both of which work at the Application Layer-7 of the OSI 7-layer model. There is some debate about which of these will become dominant in future VoIP strategies, although H.323 remains the more established technology. The two protocols can co-exist, however. H.323 is made up of lower-level protocols that manage digital voice transmission. These protocols include signalling, security, controls for transferring data between domains, call initiation and termination. As a result, any hardware conforming to the standard is interoperable. But, H.323's breadth is also its weakness. Inflexibility and poor scalability cause implementation problems. SIP is a newer, more flexible text-based protocol. It describes data being transmitted using MIME or XML, and generates a connection between two end points. SIP relies on other protocols to handle encoding, data compression and data management. Users are identified by Uniform Resource Identifiers (URIs) which allow a call to be connected by clicking on a web link, or typing in an address similar to an email. Beyond VoIP, this approach opens up possibilities for linking voice to other services, such as instant messaging and email. However, this requires a phone with a suitable keyboard for typing URIs. SDP The Session Description Protocol is generally used in conjunction with SIP to describe the attributes of a SIP session. Its parameters are included in the message body of a SIP request. Although described as a protocol, SDP is more of a format for describing multimedia sessions. ©IPK30/04/17 Few organisations will eliminate circuit-switched PBXs in the near future. This means connecting disparate networks together is an essential part of VoIP. The Media Gateway Control Protocol (MGCP) handles this. It works in with both H.323 and SIP, either of which can provide call control, while MGCP manages the connections between disparate technologies. Once a connection has been made between two endpoints, voice data is broken down into packets and transmitted across the network in real time. Creating realistically sized packets without compromising audio quality uses one of several G-series speech compression algorithms. G.711 is the most established algorithm for this purpose, but its 64Kbps bandwidth requirement is a drawback. However, it is mandatory in H.323-compliant networks. Speech compression algorithms with more modest bandwidth needs include G.729A, which offers some of the best features for VoIP. It combines small packet sizes with the voice quality of G.711 and delivers a transmission rate of 8Kbps. As quality is so essential to voice transmission, delayed transmissions or dropped packets become more apparent in this type of application than in data-related tasks. Two main protocols are used to ensure effective real-time delivery. RTP Real-time Transport Protocol provides timestamp and control functions, ensuring data is reassembled in the correct order at its destination. Data is buffered at the receiving so it is replayed at a constant rate, eliminating jitter. Its components include: sequence numbers, used to find lost packets payload identification, describing the media encoding used, which enables it to adapt to changes in bandwidth timestamp, used by the receiving client to 'play' the packet using the same timing used during transmission. This should detect and compensate for delay jitter. However, RTP does not provide any congestion or reliability control, and is not sufficient on its own to ensure effective transportation. RCP Real-time Control Protocol complements RTP by monitoring the quality of the end-to-end link. RCP packets and RTP packets are mixed and sent between senders and receivers. The RCP packets provide feedback on data transmission quality, and help identify any problems. RTP and RCP work independently of the underlying transport layer. RTP uses UDP rather than TCP, as it is better for real-time traffic. Bandwidth management. Limited bandwidth, latency and network congestion are major problems for VoIP implementations. H.323 has some integrated bandwidth management capabilities, but both this older protocol and SIP can work with more modern alternatives such as Resource Reservation Protocol (RSVP). It enables the sending mechanism to request a specific level of service across the network. Each node across the network path between sender and receiver is contacted to reserve network bandwidth. RSVP alone is not sufficient to guarantee QoS. Other, more generic measures are also required. These could include Type of Service (ToS), also referred to as IP Precedence and Differentiated Services. Both data and voice applications can be managed using these features. Network requirements for VoIP are more stringent than those for a data-only setup. Packet loss and delivery delays that would not be evident in a data application result in unacceptable quality when applied to voice. This means the architecture and design of the network are more important. Understanding component-level resilience to failure, establishing how the network can reconfigure itself in the event of such a breakdown and ensuring alternative paths are built in are all essential. Firewalls can also create bottlenecks, impacting QoS. As a result, redesigning a network's architecture is often a precursor to enjoying the cost benefits of VoIP. -VPN Virtual Private Network. Used for two applications: the first is to link two or more LANs together, the second is to allow remote and mobile users to connect to a central office network. In each case the Internet is used to provide the connection so providing a cheap solution. A VPN prevents anyone unauthorised from accessing the network. A VPN must ©IPK30/04/17 authenticate remote users and sites and then encrypt everything that makes up the communications. The encrypted data can be wrapped inside normal IP packets and routed across the Internet for decryption by other gateways or client VPN software - a process known as tunnelling. Authentication often uses DES (Data Encryption Standard), 3DES or AES (Advanced Encryption Standard) algorithms. Key management often handled by IKE (Internet key Exchange). The tunnelling protocol often uses L2TP (Layer 2 Tunnelling Protocol) in Windows 2000. Devised by Cisco and Microsoft. L2TP uses IPSec (IP Security protocol from the IETF - Internet Engineering Task Force). Does have trouble traversing NAT (Network Address Translation ) gateways. VPN functionality is included as part of RRAS (Routing and Remote Access Service) in Windows 2000 server. -VRAM Video random Access Memory. DRAM found on video controllers. Can be accessed simultaneously by two devices, so that the digital to analogue converter RAMDAC can supply screen updates while the processor is supplying data. Dual port so that it can read and write data on the same clock cycle. -VRML Virtual Reality Modelling Language, a set of codes used for writing files in 3D. Requires a special browser to view. -VRRP Virtual Router Redundancy Protocol. Allows a collection of physical routers to be viewed as one virtual router. -VSDL Very high speed Digital Subscriber Line. Offers 14Mbps down stream and 3Mbps upstream, over fibre connecting BT's exchanges to street cabinets. -VSS Volume Shadow copy Service - MS Windows 2003 -VST Virtual Studio Technology. Music editing technology - first implemented by Steinberg and made open source. -VxD Virtual Device Driver. A special type of device driver that has access to the core of the operating system for supervising hardware operations directly. A mouse, serial port and parallel port use VxDs. WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW -W3C World Wide Web Consortium. The forum for addressing Web related issues. Set up in 1994. -WAI Web Accessibility Initiative -WAIS Wide Area Information Servers -WAN Wide Area Network. Spans a wide geographical area, linking together LANs, e.g. JANET. -WAP Wireless application protocol. Designed to allow Web content and other services to be sent directly to mobile phone displays. Supported by Motorola, Nokia and Ericsson ©IPK30/04/17 -Warchalking Open Node Identify the zones of unsecured wireless networks. Closed Node WEP Node -Wavetable Synthesis The successor to FM synthesis, wavetable synthesis can store samples of musical instruments and can use them to generate quite realistic sounding music. -WCDMA Wideband Code Division Multiple Access -WDM Wavelength Division Multiplexing. To increase the capacity of the fibre, multiple wavelengths are used. As each fibre carries multiple wavelengths, need to ensure that they are kept far enough apart to ensure that their dispersion does not cause the wavelengths to overlap and interfere with each other. Lasers also drift so frequencies can shift. -Web 2.0 Essentially describes what has been happening in the development web in the specific period of time from 2001 to present. Includes dominance by major companies, Amazon, Google, e-Bay etc -WEBM Web-Based Enterprise Management -Web server A computer that serves Web pages. On the request for a page, it receives the request and sends the page back to the web browser. -WebSphere An e-commerce server product from IBM. It creates e-commerce sites and applications based on Java -WECA Wireless Ethernet Compatibility Alliance - trade association created to promote interoperability between different vendors 'WLAN equipment. -WEEE Waste Electrical and Electronic Equipment Directive. Puts the onus on the manufacturer. The directive states that the rate of recovery of materials shall be increased to a minimum of 75% by weight. The targets have to be met by 1st January 2006. The regulations are due to come into place on 13th August 2005. -WEP Wired Equivalent Privacy - the default encryption scheme used by 802.11x equipment and comes in either 40bit or 104bit key formats. A 24 bit random initialisation vector (IV) is prefixed to the key to give the full key stream. This ensures that no two packets are ever encrypted using the same key. Before being encrypted the data has a checksum calculated and appended to the packet. This will ensure that the data is correctly decoded after transmission. Once the checksum has been calculated the RC4 algorithm performs an exclusive OR between the full key stream and data/checksum combination. The encrypted data is then sent across the network with the IV transmitted in plain text. At the other end the receiver takes the IV and prefixes it to the WEP key and performs another XOR. This reverses the encryption process and checks the checksum. Uses static encryption keys. ©IPK30/04/17 -WFM Wired For Management. Intel's specification for automating client management. -WHDI Wireless High Definition Interface. Primarily designed to deliver uncompressed data to flat panel televisions. It operates in the 5GHz band. Theoretical maximum data rate is 1.5Gb/s Whois search Finds the name, address and details of a domain name's registrant -WHQL Windows Hardware Quality Labs certification - means that drivers have been scrutinised by Microsoft's testers for compatibility with Windows OSes. -WHS Windows Script Host. In Windows setup - Accessories. Disable to stop Java and VB scripts running. -Wide SCSI A SCSI standard that transfers data at 40MB/s. -WIDL Web Interface Definition Language - an XML application to allow web resources to be described as functional interfaces that can be accessed by remote systems using standard web protocols. -Wi-Fi 802.11b networking standard -Wild virus A virus in circulation. Currently there are about 250 wild viruses in the world. -WiMax A new wireless broadband technology that promisesup to 70Mb/s over distances of up to 30km. It will support advanced encryption systems from the beginning. Uses the 802.16 networking standard. Uses signals in the 3.5 and 5.8GHz band. Current power limit is 2W. WiMax technology based on 802.16d and in the near future 802.16e. -WIMP Windows, Icons, Menus, Pointers -WINA20.386 Concerned with the use of high memory. Provides backwards compatibility with Windows 3.0. Not needed for later versions. -Windows key* Break d e m r shift, m -Windows System properties Go to desktop Open My computer Minimise all windows Run Restore all windows Disposable temporary files: ~*.*, _*.*, *.??_, *.??~ Needs Times New Roman, Arial and Courier. Win95 - right click any item for a menu of common commands that apply to it. ©IPK30/04/17 To make toggle keys sound when pressed; Control Panel, double click Accessibility options, select Toggle keys and click OK. PrintScreen key captures the entire screen to the clipboard, Alt Print Screen captures just the current window or dialogue box. EDITING Msdos.sys (Remember it is Read Only!!) Use attrib -s -h -r msdos.sys before editing and then attrib +s +h +r msdos.sys after. It is in the root directory of the start up drive. Under Options; BootMenu=1 forces windows to display a menu of options each time the computer is started. Press the required letter to select. If no choice is made then windows will select the default. To set the default use BootMenuDefault=(number). To determine how long Windows waits before using its default time of 30s, type a line like BootMenuDelay=10 which will make it delay 10s. Bootdelay=0 will give the Startup menu as soon as possible. Change BootGUI from 1 to 0 to stop windows booting automatically. Only OSR2 runs Scan disk automatically after an improper shutdown. Autoscan=0 Never run scandisk Autoscan=1 Run scandisk after prompt Autoscan=2 Run scandisk without prompt Logo=1 Show W95 logo screen Logo=0 Don't show logo screen (Can fix some incompatability problems). Bootmulti=0 Windows95 Bootmulti=1 Old DOS version. Startup Menu DOS sets an environment variable %Config% to the name of the menu item that was chosen; this is the short name that appears after 'menuitem=' The program that launches Windows is Win.com. Restart the computer in MS-DOS mode. At the C:\Windows prompt type ren win.com xxxx.com Win95 can access up to 4Gb of memory. FAT16 can handle partitions up to 2Gb, by using clusters of 32Kb. FAT32 can handle partitions up to 2Tb and can use 4Kb clusters up to partitions of 8Gb System resources; composed of two heaps each of which is only 64Kb. (W95 has other heaps which are not size limited). The closer either heap gets to being filled, the more unstable Windows becomes. The two heaps are GDI, which stores images for onscreen displays, and User, where programs keep windowing and other information. The Resource meter shows whichever of the two is worse off at the current moment. The only way to clear a heap is to exit and then re-enter Windows. Keyboard shortcuts. Ctrl + x to cut selected text. Ctrl + c to copy selected text. Ctrl + v to paste selected text. Ctrl + g for the goto option (in Windows Explorer) Ctrl + z to undo the previous action. Ctrl + a to select all files or text. Ctrl + F4 to close the active document window. Ctrl + F6 to switch between open documents. Ctrl + Esc brings up the Start menu. Ctrl + Esc + r to open the Run dialogue box. Ctrl + drag a file to a folder to copy a file. Ctrl + Shift + drag a file to the desktop or a folder to create a shortcut. Ctrl as Windows restarts prevents Startup group applications from loading. Shift + F10 to open task bar properties. Shift + delete to delete items without putting them into the Recycle bin. ©IPK30/04/17 Shift + inserting a CD to disable Autorun Alt + F4 to close a windows one at a time. Alt + enter to view the properties of a selected item. Alt + spacebar to access the window menu in any window. Alt + spacebar + c closes the active window Alt + spacebar + m moves the active window position using the arrow keys. Alt + spacebar + n to minimise the active window. Alt + spacebar + s resizes the active window using the arrow keys Alt + spacebar + x to maximise the active window. Alt + tab to toggle between open programs. Backspace (in Explorer) goes straight to the parent folder. Function keys. F1 Help. F2 to rename a selected file or folder. F3 to find a file or sub-folder. F4 displays the combo screen (in Explorer). F5 to refresh the screen. F6 to switch panes in Explorer. F8 for special boot menu option like Safe mode. F10 for menu access. Deleting icons from the desktop. Use Registry editor and get to Hkey_local_machine\software\Microsoft\Windows\fflCurrent Version\explorer\Desktop\Namespace. From here, select an alphanumeric key in the namespace folder and the keys corresponding icon name will appear in the righthand pane under data. When you find the icon that you want to lose, right click its key in the left hand pane and select delete. Close the Registry Editor, click on the desktop once and then press F5 to refresh. W95 Version. Right click My computer and select properties. Under the general tab is the version number. 4.00.950 original version. 4.00.950a original version updated with Service pack 1. 4.00.950b OSR2 (OEM Service release 2) 4.00.950b* OSR2.1 adds universal serial bus support. Resources kit. Contains much useful information. CD:\Admin\Reskit\helpfile win95rk.hlp Updates to W95. To list updates to the system run Qfecheck.exe (in c:\Windows). Windows95 Service Packs www.microsoft.com/windows/software/servpak1/sphome.htm It is free of charge. To Print from Explorer. Not a standard option. Can be added to the context menu by:-In Explorer, select View, Options, then click on the File Types tab. Scroll down until you see the Folder type. Select it and click Edit. In the Edit File Type dialogue click New. In the New Action dialogue enter a name for the action like List or Print; this will appear in the menu. In the Application used to perform action field, type: command.com /c dir"%1" /o>prn Close all the dialogues and the new option now appears in your folder context menus. Duplicate files. W95 creates a lot of duplicate files. In c:\windows\sysbckup it keeps copies of many files that are in c:\windows\system so that it can replace these files in the event of an errant Setup Program. These should NOT be deleted. For other files if one copy is in either c:\windows or c:\windows\system, then you can safely delete any other copies. Windows will look in either of these places if the file it needs isn't found in an applications home directory. ©IPK30/04/17 To prevent a CD auto running:a). Hold down the shift key until the drive drawer is closed and Windows has read the disk, b). Control panel, System, CD ROM driver, click Properties, clear the box next to Auto Insert notification, click OK and close. Power toys for Windows 95: TweakUI control panel accessory. Enables the control of the windows animation and many other aspects of the user interface. From the DOS prompt Extract win95_03.cab /l c:\windows himem.sys The command extract/A win95_02.cab /D filename l MORE lists all the Windows 95 cab files and shows which one contains the file 'filename'. The file extension '.ico' is used for shortcut file extensions. Essentially they are bit maps. Win95 screens. logow.sys Windows is shutting down screen logos.sys It is safe to turn off your computer screen logo.sys Startup screen. Root directory, 256 colours by 320x400 pixels Screen Savers. To prevent it operating in Win95 ensure that the Start menu is displayed. Reclaiming Disk Space. Files to delete: *.tmp unless it has todays date. *.bak Though beware of system files. *.gid These are index files that are built the first time you use Find to search the help file. Documents. To clear the Documents record go to c:\Windows\Recent and delete the files and short cuts. Make Notepad a Send To destination. Windows folder, find Notepad, position the left hand window pane so that the SendTo folder is visible, then drag Notepad to the SendTo folder. Now select the SendTo folder, select the shortcut to notepad.exe icon and rename the shortcut to just Notepad. To view an unknown file type, right click the file icon then select SendTo Notepad. Cannot remove an NT partition using the normal FDisk. Need to use Partition Magic or the equivalent. To remove a file association, double click on My Computer, then choose Options from the View menu and click the File Types tab. Scroll down the list, select the file and click Remove. Microsoft RegClean 4 will clear any dross from the registry. Windows set up problems. Various switches available. Run Setup/?from the command line to list these options. /C=run without using the disk cache /D=clean install, ignoring existing Windows installations (better to reformat!) /ID=skip the disk space check /IE=skip creation of a startup disk /IH=skip the Registry validity check /IM=skip the memory check /IN=run Setup without the Network Setup Module. Not able to run Network connection after. /IP=skip detection of unknown plug and play /IQ=skip the check for cross linked files /IR=skip the detection of system Bios /IS=skip the ScanDisk disk check /IV=skip the display of information screens during setup /L=Loads a Logitech mouse driver instead of a Microsoft one /M=suppress playing of WAV sounds ©IPK30/04/17 /N=run without mouse support /NM=bypass CPU detection enables Windows to be installed on lower spec machine! /Nostart=performs only the copy part of the installation not the setup. /NTLDR=bypass check for existing operating system - prevents OEM versions of Windows from being installed on a PC with an existing Windows installation. /T:<dir>=specifies the location Setup will use for its temporary files. /P<option list>=allows diagnostic options to be selected during Setup. Multiple options should be separated by ; e.g. Setup/Pb;f where b=enables Prompt before Mode, allowing you to choose whether to run each device detection module. f=enables clean registry mode, which ignores info about previously detected hardware in the registry (Win95 only) i=bypasses detection of unknown plug and play Bioses and devices (those not listed in machine.inf) j=installs ACPI support in Win98 only. Printer port may need reconfiguring using Bios setup before ACPI will work properly. -WinFX The application programming interface (API) used in Vista. FX stands for Framework Extennsion and WinFX is a literal extension of the .net Framework. It will replace Win32. -WIN.INI The windows equivalent of the autoexec.bat file. Deals with the software. Placing a ; infront of a line in Winini disables the line. -WINS Windows Internet Naming Service -Win95 To boot to a DOS prompt. In DOS type Attrib -s -h -r msdos.sys Edit msdos.sys Change the line that reads BootGUI=1 to BootGUI=0 Save the file and quit edit. Attrib +s +h +r msdos.sys To run windows from the command prompt type Win Windows 95 can read up to 4GB of memory. To prevent the applications in the start up folder from loading at bootup hold down the shift key as Windows loads. American keyboards in Dos - add a line to the AutoExec.bat file KEYB UK -Windows98 Hold down CTRL key and reboot to get to command prompt. To access the Boot menu hold down the shift key during bootup. To restore registry c:\ then run ScanReg.exe Stop background utilities starting by holding down Shift while Windows starts. Run Scandisk in DOS to speed up process. To clean up the hard disk - right click C. Select properties. Click the Disk Cleanup button. Finds all disposable files. Speed up W98 If more than 64MB memory reduce swap files by:run sysedit, select system.ini. Scroll down to the section headed by the line [386Enh] and then add a line at the end of the section ConservativeSwapfileUsage=1 There is a bug in W98 which causes summer time adjustment even if it is unchecked. This can be overcome by setting the time zone to Casablanca. System File Checker - used to check system files on W98. Run SFC. ©IPK30/04/17 If a system won't even boot to safe mode then boot from a boot disk and then type SCANREG/FIX from the command prompt. -WindowsNT Useful for multitasking, added security, multiprocessor systems, runs demanding applications, running SCSI disk arrays. Has its own filing system, NTFS. NT cannot recognise FAT32 partitions on Win9x systems and vice versa. Will support FAT16 though. Event viewer logs critical system activity including crashes. launch from Start, Programs, Administrative Tools, Event Viewer. Colour coded, blue for information, yellow for warning, red for error. User Manager. Start, Programs, Administrative Tools, User Manager for Domains. Choose Policies, Audit, Audit these events. To kill an App in NT, right click the Taskbar and click Task Manager. Click the Applications tab and select the hung-up program from the list of running tasks. Click the End Task button. -W2000 turns off the packet handling for network cards. www.registry.winguides.com Under the registry key: HKEY_LOCAL_Machine\System\CurrentControlSet\Services\TCPIP\Parameters create a new DWORD value with a name of DisableTaskOffload and give it a value of 0. W2000 server fully supported until 310305 - ends 310307 W XP Pro server fully supported until 311206 - ends 311208 -Windows XP Recovery Console. Install from CD - Run - D:\i386\winnt32.exe/cmdcons To disable a service, the command is disable service_name/device_driver_name e.g. to disable the eventlog type disable eventlog Batch files. Can contain any of the commands of the Recovery Console but cannot contain another batch file. Syntax batch input_file [output_file] Output files are not necessary, but if specified will store the results of the commands listed in the input file. If the output file is not specified then the results are output to the screen e.g. batch E:\myfiles\find.txt c:\mytests\results.txt bootcfg/rebuild will attempt to rebuild the boot.ini file -WINS Windows Internet Naming Service -Winsock A program that provides Windows with a standard way to communicate with the Internet. Any Windows based PC needs one; often provided by the ISP. -Wireless Frequency bands available for short range devices in the UK are at 173MHz, 433MHz, 458MHz, 868MHz, 2.4GHz, 3.4GHz and 5.8GHz. 3.4GHz intended for commercial providers to connect to homes. Intended to support a protected quality of service with licences allocated to a number of regions. Could be used to support broadband beyond the reach of ADSL and cable. -WLAN Wireless Local Area Networks - also known as WiFi. Europe uses DSSS (Direct Sequence Spread Spectrum) on 13 different frequency channels on the 2.4GHz - ISM band (Industrial, Scientific, Medical). There are only two combinations of a maximum of three channels that can be guaranteed not to interfere with one another. These are 1-7-13 (most frequently used in Europe)and 1-6-11 (most frequently used in the USA. The FCC - 2.4GHz ISM band is shorter and does not contain channels 12 and 13. ©IPK30/04/17 The 2.4GHZ ISM band is from 2.4 - 2.4835GHz. ETS 300328 (European Telecommunications Standard) limits the transmission power to 100mW at 1m from the aerial. -WMA Windows Media Audio -WMV Windows Media Video -Word Versions of Word earlier than 6.0c require the presence of the file share.exe, even though it is functionally built into Windows 95 and Windows 98. Needs to be placed into the root directory of C. Can use a null length file called share.exe to fool the program. Settings file NORMAL.DOT. Ctrl+Shift+z turns off sub and superscripts. -Workgroup A sub-section of a larger network or a small LAN (up to 50 users). -WPA Wi-Fi Protected Access. A subset of 802.11i A WEP replacement that uses rotating keys. -WSC Windows Server Clustering -WSDL Web Service Description Language. An upshot of XML. It provides a mechanism through which a device newly connected to a network can announce its presence and describe what it can do. Jointly developed by Microsoft and IBM, this is essentially the language used by the UDDI registry. -WSH Windows Scripting Host -WSRP Web Services for Remote Portlets -WTLS Wireless Transport Layer Security. Used on WAP phones. -WWDM Wide Wave Division Multiplexing -WWW World Wide Web -WYSIWYG What You See Is What You Get. -WYSIWYG editor Software such as MS FrontPage or Macromedia Dreamweaver that helps you create a Web site. XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX -X.21 CCITT (ITU) standard governing interface between DTE and DCE for synchronous operation on public data networks. -X.25 CCITT (ITU) standard governing interface between DTE and DCE terminals operating in the packet mode on public data networks. ©IPK30/04/17 -X.25 PAD A device that permits communication between non-X.25 devices and the devices on an X.25 network -XAUI 10Gbps Ethernet Attachment Unit Interface. Used with 10GB Ethernet MAC. Pronounced "Zowie" -XBASIC Freeware BASIC interpreter. www.maxreason.com -XDE Extended Development Environment -XHTML Extensible Hypertext Markup Language. The successor to HTML. XHTML1.0 became a W3C recommendation in January 2000 and work on XHTML2 is well advanced. -XIP Execute In Place. Software places on a PCMCIA ROM card can be executed from the card instead of being loaded into RAM first. -XLL Extensible Linking Language. Provides Hyperlinking in XML. -XML Extensible Mark-up Language. Similar to HTML as a language for page construction. A meta language - used to describe other languages. Devised by the World Wide Web consortium group. Open format. Meant to be readable by anyone. XML defines the document structure itself. Contents should be visible in plain text. Any device with an XMLenabled browser can render a version of the same document but do so in a way specifically designed for the device being used. XML interacts with the Document Object Model. XML is a subset of SGML. -Xmodem A file transfer protocol. Transmits 128byte blocks and was the first FTP for PCs. It performs a checksum on packets to help ensure accurate transmission. The sending computer uses an algorithm that calculates the binary values in a packet and sends the result as a tail on the packet. The receiving computer goes through the same algorithm. If the two sums do not match, then it requests that the packet be resent. -XMS See Extended memory. -X-ON/X-OFF Transmitter On/Transmitter Off. Control characters used for flow control, instructing a terminal to start transmission (X-ON) and end transmission (X-OFF). -XSL Extensible Stylesheet Language part of XML. Has three parts XSLT, which handles the transformations of one XML file into another. XPath, which is a language used by XSLT to access or refer to parts of an XML document and XSL Formatting Objects, which handles the actual formatting. More powerful than CSS. -XT Extra Technology. An IBM model designation now generally accepted to mean any PC with a 8088 or 8086 CPU YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY ©IPK30/04/17 -Ymodem A file transfer protocol. This transmits 1KB blocks and adds batch file processing to Xmodem. Both Xmodem and Ymodem are stop and wait protocols. The sending computer transmits, then waits to receive an acknowledgement from the receiving computer. A NAK (negative acknowledgement) indicates a bad or missing packet and requests that the sending computern resend the packet. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ -ZIF socket Zero Insertion Force socket. -ZigBee (IEEE802.15.4) A very low power, limited range wireless system. It defines a network mesh where multiple paths exist between nodes. This provides redundancy and resilience. Designed for very low power drain and primarily used for industrial control and building automation. -Zmodem A file transfer protocol. This is a streaming protocol. The sending computer sends packets until it receives a negative acknowledgement (NAK). It then backs up to the bad packet and resends from there. Can also adjust packet size depending upon line conditions. If interrupted it can restart and resume from the point at which it was interrupted. Often used for satellite transmissions because of the changeable line conditions. -Zone transfers Requests to DNS servers for all available information. Should be disabled for all except secondary DNS servers. -Zoo viruses Live mostly within research labs and have not escaped into general circulation. Currently about 18000 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ Binary File Reader File Analyzer http://spybot.safenetworking.de Hacker site www.cultdeadcow.com www.coderz.net Internet glossary http://www.webopedia.com/ Lock picking www.wilton.force9.co.uk/lock Stickies www.tomrevell.btinternet.co.uk Trivia www.didyouknow.com Winsock Software. (The Ultimate Collection Of ) www.tucows.com Win98 Magnify. magnify.exe and mag_hook.dll. Put in any folder in Win95 machine. DVD sites. www.7th zone.com ©IPK30/04/17 www.dvddemystified.com/dvdfaq.html Free File decompression program - Aladdin Expander - www.aladdinsys.com www.fileworld.com Notepad+, Notemaid. www.privacyfoundation.org turning off java script in e-mails. www.anonymizer.com Enables you to visit web sites anonymously. www.fourmilab.ch/documents/dvdregion/ contains an article explaining how to play DVDs with any region code using the Microsoft DVD player. http://regionhacks.datatestlab.com http://web.icq.com/sms details on how to unlock DVDs Free web based SMS messaging service www.ultrafunk.com Popcorn E-mail system http://mathsworld.wolfram.com www.driverguide.com www.crucial.com www.jumbo.com ZoneAlarm firewall www.zonelabs.com Basic Java Development kit from www.javasoft.com Free versions of C, C++ and Pascal from www.gnu.ai.mit.edu www.monkey.org/~dugsong dsniff network sniffing tools http://hubble.stsci.edu www.dimension music.com/mp3 www.microsoft.com www.intel.com www.which.net www.oft.gov.uk www.RAM.UK.COM www.teachers.org.uk www.becta.org.uk www.bug2000.co.uk www.cerncourier.com research.unilever.com www.newscientist.com www.teaching-today.com www.psionda.com.com www.wdc.com Microsoft Intel Consumer Association Office of Fair Trading RAM computers NUT Government bug Y2K Particle physics and physics web sites Unilever New Scientist on-line daily teachers newspaper. Psion Dacom Western Digital ©IPK30/04/17 www.hcs.ndirect.co.uk/free.htm Bios passwords: Killcmos. http://www.netcraft.com Useful site for finding out details of other web sites http://airsnort.shmoo.com Airsnort requires 5 to 10 million packets to be gathered from a wireless LAN before cracking the key. http://sourceforge.net/projects/wepcrack WLAN cracker www.kismetwireless.net Kismet sniffs for unprotected WLANs www.remote-exploit.org Wellenreiter sniffs for unprotected WLANs www.apache.org/httpd.html version for Win32 Download version of Apache web server - choose Security Scans www.grc.com www.hackerwhacker.com Rambooster www.saunalahti.fi/%7eborg/rambooster Medical www.pathfinder.com/drwell www.thriveonline.com www.netdoctor.co.uk SMS to mobiles www.breathe.com Reference www.britannica.com www.howstuffworks.com www.diyfixit.com www.streetmap.co.uk Computer reference www.pcshowandtell.com www.whatis.com Eliminate the need for on-line registration www.bugmenot.com http://bobby.watchfire.com/bobby/html/en/index.jsp a free service which checks web pages according to W3C standards and US Section 508 guidelines