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BA 1306 Information Systems and Programming Asst. Prof. Engin Kucukkaya BA 1306 Spring 2007 Introduction Lecture Outline: The Big Picture Hardware Data Communications The Internet Classification of Computers Software BA 1306 Spring 2007 The Big Picture The computer systems have three main components: Hardware, software and people. The equipment associated with a computer system is called hardware. The programs, or step-by-step instructions that run the machines, are called software. Computer programmers write programs for users, or end-users — people who purchase and use computer software. BA 1306 Spring 2007 Hardware A computer is a machine that can be programmed to process data (input) into useful information (output). A computer system requires four main aspects of data handling: ● ● ● ● Input Processing Output Storage. BA 1306 Spring 2007 Hardware: The basic components ● Input is data to be accepted into the computer ● ● Common input devices are keyboard, mouse, joystick, and scanner. Storage devices and communication devices can also be used for input. BA 1306 Spring 2007 Input A keyboard is a common input device that may be part of a personal computer or a terminal connected to a remote computer. A mouse is an input device with a ball on its underside, whose movement on a flat surface causes a corresponding movement on the screen. Moving the mouse allows you to reposition the pointer, or cursor, an indicator on the screen that shows where the next interaction with the computer can take place. Mouse technology is now shifting towards optical mouse, where light beams emitted by the mouse are used to capture the movement. BA 1306 Spring 2007 Input A trackball is like an upside-down mouse—the ball is rolled with the hand. A touch pad invokes a command with finger movement. BA 1306 Spring 2007 Input A scanner converts text, drawings and pictures into computer-recognizable form Types of scanners Flatbed Sheetfeed Handheld Overhead Drum Overhead Handheld BA 1306 Spring 2007 Sheetfeed Input Voice input, or speech recognition, is the process of presenting input data to the computer through the spoken word. Speech recognition devices convert spoken words into a digital code that a computer can understand. The two main types of devices are BA 1306 Spring 2007 Input Input can be given directly to a computer via a touch screen; a finger touching the screen interrupts the light beams on the monitor edge, pinpointing the selected screen location. A user can deliver input to a computer by looking at a screen, assuming electrodes are attached to the skin near the user's eyes so that their signals can be read by the computer system. BA 1306 Spring 2007 Hardware: The basic components The processor, or central processing unit (CPU), processes raw data into meaningful, useful information. The CPU interprets and executes program instructions and communicates with the input, output, and storage devices. Main Memory, or primary storage, is connected with the central processing unit but is separate from it. Memory holds the input data before processing and also holds the processed data after processing, until the data is released to the output device. BA 1306 Spring 2007 CPU The CPU interacts with memory (not a part of CPU), i.e. the primary storage, to get instructions and data Secondary storage holds permanent data on some external medium INPUT CPU Control Unit OUTPUT Arithmetic/ Logic Unit Memory BA 1306 Spring 2007 SECONDARY STORAGE How does the CPU work? Control unit directs the movement of instructions and data between memory, ALU and secondary storage OUTPUT INPUT Control Unit Arithmetic/ Logic Unit Memory BA 1306 Spring 2007 SECONDARY STORAGE Components of CPU Control Unit: directs the entire computer to carry out the program instructions. It does not actually execute instructions, it makes other parts to do so. – – – •Arithmetic/Logic Unit: – It executes all arithmetic – – and logical operations. – – – – addition (+) subtraction (-) multiplication (*) division (/) equal to (=) less than (<) greater than (>) less than or equal to (<=) greater than or equal to (>=) less than or greater than (< V >) BA 1306 Spring 2007 Components of CPU Registers are: temporary storage locations for instructions or data not parts of memory, but parts of CPU very fast under the control of the control unit Registers accept, hold, transfer instructions or data hold data about immediate operation being executed, as compared to the memory that holds data about near future BA 1306 Spring 2007 Speed and Power Execution of an instruction on a slow computer is measured in milliseconds Now we are at the age of nanoseconds (one billionth of a second) MHz: millions of machine cycles per sec. 133 MHz SDRAM : 7.5 nanoseconds per cycle GHz: billions of machine cycles per sec. BA 1306 Spring 2007 Memory Memory is the part of the computer that holds data & instructions for processing Main memory holds the instructions and relevant data of an application as long as it is in operation BA 1306 Spring 2007 Data Representation Data is represented in two states: electricity high and low This is called the binary system Each 0 or 1 is a bit, this is the basic unit for storage BA 1306 Spring 2007 Data Representation Bits are put together to a group called byte. There are usually 8 bits in a byte Notation: 210bytes = 1024 bytes = 1 Kbytes 220bytes = 1024 Kbytes = 1 Megabytes 230bytes = 1024 Mbytes = 1 Gigabytes BA 1306 Spring 2007 Data Representation ASCII: American Standard Code for Information Interchange 8 bits for each character Therefore, 256 (28)characters exists in ASCII-8 A: 0100 0001 B: 0100 0010 C: 0100 0011 D: 0100 0100 … BA 1306 Spring 2007 Storage Locations and Addresses A memory location can only hold fixed amount of data The location in memory for each instruction and piece of data is identified by a memory address Memory Address of a location remains the same, but the contents may change In programming, you need not worry about the physical memory locations, instead we use symbolic addresses BA 1306 Spring 2007 Chips in your PC Memory Types (RAM) SIMM: Single in-line memory module DRAM: Dynamic RAM SRAM: Static RAM SDRAM: Synchronous dynamic RAM DDR SDRAM: Double Data Rate SoDIMM: Small outline dual inline memory module (used in portable computers) BA 1306 Spring 2007 Speed and Power Cache is a relatively small block of very fast memory that is designed to speed up the internal transfer of data and instructions Internal Cache: built into the processor External Cache: built on separate chips RISC: Reduced instruction set computer Parallel processing: a method of using several processors at a time, this is the ultimate speed solution used on servers BA 1306 Spring 2007 Hardware: The basic components Output, which is raw data processed into usable information, is usually in the form of words, numbers, and graphics. Users can see output displayed on a screen (also known as monitor), or use printers to display output on paper. BA 1306 Spring 2007 Output The monitor is a device that receives video signals from the computer and displays the information for the user. It supports high-resolutions when compared to regular TV screen. The digital copy of a file that can be seen on a screen or that can be stored on a storage media is known as soft copy because it is intangible and temporary, unlike hard copy, produced by a printer on paper, which is tangible and can be permanent. BA 1306 Spring 2007 Output A computer display screen that can be used for graphics is divided into dots that are called addressable because they can be addressed individually by the graphics software. Each screen dot is called a pixel. The more pixels, the higher the screen resolution, or clarity. Dot pitch is the amount of space between the dots on a screen. BA 1306 Spring 2007 Output CGA (Color Graphics Adapter) 2 colors at a resolution of 640x200. EGA (Enhanced Graphics Adapter) resolution of 640x350 with up to 256 colors. VGA (Video Graphics Array or Video Graphics Adapter) 640x480 display showing 16 colors. SVGA (Super-VGA) resolution of 800x600 with support for 256 colors or 1024x768 with 16-color support. XGA (eXtended Graphics Array or Extended Graphics Adapter) resolution of 1024x768 in 256 colors or 640x480 in high (16-bit) color. SXGA (Super XGA) A screen resolution of 1280x1024 pixels UXGA (Ultra XGA) A screen resolution of 1600x1200 pixels. BA 1306 Spring 2007 Output Printers produce printed paper output. Printers can be classified as either impact printers, dot matrix, which form characters by physically striking the paper, or Non-impact printers, laser and ink-jet printers, which use a non-contact printing method. Today's laser printers print usually at 600 dpi (dots per inch), producing extremely high-quality results. BA 1306 Spring 2007 Storage and Multimedia Secondary storage provides additional storage space separate from memory. The most common secondary storage devices are magnetic disks Hard disk Flash Disk and optical disks CD-ROM DVD BA 1306 Spring 2007 Secondary Storage Secondary storage is the type of storage that is separate from the processing By using secondary storage, software and data can be stored on a permanent or semipermanent basis. Secondary storage is necessary because memory, or primary storage, can be used only temporarily and it has limited capacity. Advantages of secondary memory space, reliability, convenience economy BA 1306 Spring 2007 Magnetic Disk Storage Diskettes and hard disks are magnetic media, Magnetic data storage is based on a technology of representing data as magnetized spots on the disk. BA 1306 Spring 2007 Magnetic Disk Storage A hard disk is a metal platter coated with magnetic oxide that can be magnetized to represent data. BA 1306 Spring 2007 Optical Disk Storage Optical disk technology uses a laser beam to enter data as spots on the disk surface. To read the data, the laser scans the disk, and a lens picks up different light reflections from the various spots. 1 bit 0 bit BA 1306 Spring 2007 Optical Disk Storage CD-ROM (compact disk read-only memory) has a disk format identical to that of audio compact disks. Regular CD-ROMs can hold up to 700 megabytes per disk. CD-RW technology permits writing on optical disks. DVD-ROM, for digital video disk, has astonishing storage capacity, up to 17GB if both layers and both sides are used. BA 1306 Spring 2007 Flash Memory Flash Memory: An electronic circuitry that offers a nonvolatile and rewritable type of memory. BA 1306 Spring 2007 Flash Memory • Flash memory is durable, operates at low voltages, and retains data when power is off. • Flash memory cards are used in digital cameras, cell phones, printers, handheld computers, pagers, and audio recorders. BA 1306 Spring 2007 Data Communications Data communications is the transfer of data between separate computing devices at various locations using telephone lines, microwave and/or satellite links. The process of data communications consists of three main operations: transmission of data reception of data validation of data BA 1306 Spring 2007 Data Communications A network is a group of stations (computers, telephones, or other devices) connected by communications facilities for exchanging information. Connection can be permanent, via cable, or temporary, through telephone or other communications links. BA 1306 Spring 2007 Data Communications The basic components of a data communications system are a sending device, a communications link, and a receiving device. BA 1306 Spring 2007 Data Transmission Computers produce digital signals, but most types of communications equipment use analog signals. Digital transmission sends data as distinct on or off pulses. Analog transmission uses a continuous electric signal in a carrier wave having a particular amplitude* and frequency. *amplitude: The maximum height of a wave. BA 1306 Spring 2007 Data Transmission Digital signals are converted to analog signals by modulation (change) of the amplitude of the carrier wave. Demodulation is the reverse process (conversion from analog to digital). Both tasks are performed by a device called a modem. BA 1306 Spring 2007 Data Transmission Simplex transmission allows data to move in only one direction (either sending or receiving). Half-duplex transmission allows data to move in either direction but only one way at a time. With full-duplex transmission, data can be sent and received at the same time. BA 1306 Spring 2007 Data Communications Often organizations use a network of personal computers, which allows users to operate independently or in cooperation with other computers, exchanging data and sharing resources. Such a setup is called a local area network (LAN). BA 1306 Spring 2007 Data Communications Users who connect their computers need some type of equipment to transfer the data. Connecting to a LAN is usually realized by the use of a network adaptor (NIC) card. Users who connect their computers via the phone lines must use a hardware device called a modem to reconcile the inherent differences between computers and the phone system. For wireless connections, a WIFI adaptor, or a Bluetooth adaptor can be used. BA 1306 Spring 2007 Local Area Network A local area network (LAN) is a network of personal computers and other equipments such as printers and scanners that share hardware, software, and data, typically within a building. The nodes on some LANs are connected by a shared network cable or by wireless transmission. • A network interface card (NIC) is inserted into an expansion slot to handle sending, receiving, and error checking of transmitted data. BA 1306 Spring 2007 Local Area Network If two LANs are similar, they can send messages among their nodes by using a bridge. A gateway is a collection of hardware and software resources that connect two dissimilar networks and performs protocol conversion when necessary. BA 1306 Spring 2007 Local Area Network A router is an equipment that directs network traffic when several networks are connected together. Most of the networks that have adopted the Internet protocol (IP) use IP switches, which are less expensive and faster than routers. BA 1306 Spring 2007 Local Area Network A Firewall is an equipment which limits network access between two or more networks. BA 1306 Spring 2007 Client-Server LANs A client/server arrangement involves a server, a computer that controls the network. The server has hard disks holding shared files and often has the highest-quality printer. A file server transmits the entire file to the node, which does all its own processing. BA 1306 Spring 2007 Peer-to-Peer LANs In a peer-to-peer arrangement, all computers have equal status; no one computer is in control. With all files and peripheral devices distributed across several computers, users share each other's data and devices as needed. BA 1306 Spring 2007 Network Topologies If we have to connect several computers, we have many options to do so. The physical layout of a network is called a topology. A node usually refers to computers and peripheral devices such as printers connected to a network. Internet Mapping Project http://research.lumeta.com/ches/map/index.html BA 1306 Spring 2007 Network Topologies • A star network has a central computer, the hub, through which all traffic passes. • A ring network links all nodes together in a circular manner. • A bus network has a single line, to which all the network nodes and peripheral devices are attached. Bus Star BA 1306 Spring 2007 Ring LAN Protocols Ethernet is a network protocol that runs on bus topology. • A Token Ring network controls access to the shared network cable by using token passing. BA 1306 Spring 2007 WLAN and WiFi Wireless Local Area Network (WLAN) is a local area network that uses high frequency radio signals to transmit and receive data over distances of a hundred meters at most. It is based on the IEEE 802.11 family of standards. Wireless Fidelity (WiFi) is a WLAN using the IEEE 802.11a/b/g specifications BA 1306 Spring 2007 Bluetooth Bluetooth describes how mobile phones, computers and PDAs can easily interconnect with each other and with home and business phones and computers using a short-range (10 m.) wireless connection. BA 1306 Spring 2007 Virtual Private Network (VPN) Virtual Private Network a network in which some of the parts are connected using the public Internet, but the data sent across the Internet is encrypted, so the entire network is "virtually" private. • A typical example would be a company network where there are two offices in different cities. • Using the Internet the two offices merge their networks into one network, but encrypt traffic that uses the Internet link. BA 1306 Spring 2007 The Internet The Internet, sometimes called simply "the Net", connects users worldwide. To access the Internet, a user's computer must connect to a computer called a server, which has special software called TCP/IP (for Transmission Control Protocol/Internet Protocol) that allows different types of computers to communicate with one another. The supplier of the server computer, often called an Internet service provider (ISP), charges a fee based on the amount of service provided. BA 1306 Spring 2007 The Internet Using software called a browser, a user can use a mouse to point and click on screen icons to explore the Internet, particularly the World Wide Web (the Web), an Internet subset of text, images, and sounds linked together. Each different location on the Web is called a web site or, more commonly, just a site. A home page is the first page of a web site, and is accessed by internet users based on its address. BA 1306 Spring 2007 Protocols & TCP/IP A protocol is a set of rules for exchanging data between a terminal and a computer or between two computers. The protocol that makes Internet universally possible is Transmission Control Protocol/Internet Protocol (TCP/IP), which permits any computer at all to communicate with the Internet. TCP does the packeting and reassembling of the message IP does the addressing. BA 1306 Spring 2007 What is Internet? An internet is the collection of networks interconnected by a set of routers which allow them to function as a single, large network. • The Internet is a worldwide system of computer networks in which any one computer can get information from/or talk to any other connected computer using the TCP/IP protocols. BA 1306 Spring 2007 IP Addresses / Domain Names Whenever a computer is connected to the Internet, it is given a personal identification : the IP address (Dynamic IP). The IP address is made up of 4 series of numbers from 0-255 e.g.: 194.133.117.3 No two computers in the world can share the same IP address at the same time. When you connect to Internet, your ISP assigns an IP address to your computer. Upon disconnecting, your IP address becomes available for use by someone else. BA 1306 Spring 2007 IP Addresses / Domain Names However, server computers need to have a fixed addresses. Consider that you want to access the web site of our university. Its address has to be unique, so that you get to the correct site. The address of METU home page is 144.122.144.160. Do you have to memorize this number? No! Instead we use the domain name: www.metu.edu.tr BA 1306 Spring 2007 IP Addresses / Domain Names The method of assigning understandable names to IP addresses is called Domain Name System (DNS) The mapping of domain names and addresses are held on servers that are called as Domain Name Servers. Everytime that you want to access www.metu.edu.tr, the browser first “resolves” the address by asking it to a Domain Name Server. The main DNS Server in Turkey is operated by METU. BA 1306 Spring 2007 IP Addresses / Domain Names www.metu.edu.tr indicates that this is the address of a site on the Web is the name of the site, usually the name of the organization • COM: commercial organizations • ORG : non-profit organization. • EDU: educational institutions • MIL: military organizations • GOV: government entities BA 1306 Spring 2007 represents the name of the country in which the site is located. World Wide Web (WWW or "Web") - A system of Internet servers that uses HTTP to transfer specially formatted documents. The documents are formatted in a language called HTML (HyperText Mark-up Language). Dr. Tim Bernes-Lee HTML supports links to other documents, as who developed the concept of WWW and well as graphics, audio, and video files. wrote the first web browser One can jump from one document to another simply by clicking on hyperlinks. BA 1306 Spring 2007 HTML HTML: Hypertext Markup Language The coding language used to create Hypertext documents for use on the WWW. Basically it is a set of ‘markup’ codes inserted in a file that tells the Web browser how to display a Web page’s words and images for the user. The "hyper" in Hypertext comes from the fact that in HTML you can specify that a block of text, or an image, is linked to another file on the Internet. HTML files are meant to be viewed using a "Web Browser". BA 1306 Spring 2007 HTML <html> <body bgcolor="yellow"> The content of the body element is displayed in your browser. <p>Paragraph elements are defined by the p tag.</p> <hr> <h1 align="center">This is heading 1</h1> <h2>This is heading 2</h2> <h3>This is heading 3</h3> <h4>This is heading 4</h4> <h5>This is heading 5</h5> <h6>This is heading 6</h6> <b>This text is bold</b> ... <big>This text is big</big> <br> <em>This text is emphasized</em> <br> <i>This text is italic</i> <br> <small>This text is small</small> <br> This text contains<sub>subscript</sub> <br> <br> <strong>This text is strong</strong> <br> ... This text contains <sup>superscript</sup> <br> <a href=“http://www.metu.edu.tr”>This is a link to our university web site</a> This is the HTML code for... </body> </html> BA 1306 Spring 2007 HTML ... this web page. BA 1306 Spring 2007 Plugins A plugin is a program that is integrated into another application. The program plugs into the application. Plugins often provide additional functionality that isn't available in the application. They add functionality to a web browser. Shockwave is the most popular plugin that allows the use of sound and graphics (Flash Animations) that the browser can't handle. Quicktime is another plugin that allows watching movies, and RealPlayer is a plugin for audio files. BA 1306 Spring 2007 E-Mail BA 1306 Spring 2007 E-Mail POP3 stands for Post Office Protocol version 3 and is used to handle email between Email Server and our Local Email Client (like Outlook or Eudora). Use of POP3 protocol is activated when we click on "Receive" button in our email client. Until this happens our email will stay on the “Email Server”. SMTP (Simple Mail Transfer Protocol) is used to deliver email from our Email Client to the recipient's Email Server. The email will stay on the recipient's Email Server until it is explicitly requested to be downloaded by the recipient's Email client over POP3 protocol. BA 1306 Spring 2007 Software Software: ● ● 1. 2. 3. Telling The Machine What To Do Some Task-Oriented Software Software in The Business Environment Computers and People BA 1306 Spring 2007 Software: Telling the machine what to do Software is the planned, step-by-step set of instructions required to turn data into information. Software is what makes a computer useful. A subset of systems software is known as an operating system, the underlying software found on all computers. The operating system serves as an intermediary between the applications software and the hardware. BA 1306 Spring 2007 Operating System Operating systems perform basic tasks, such as: recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, controlling peripheral devices such as disk drives and printers running and controlling the application programs BA 1306 Spring 2007 Application Software Applications software can be used to solve a particular problem or to perform a particular task. Applications software may be either custom or packaged. Computer programmers are people who design, write, test, and implement software. Organizations may pay computer programmers to write custom software, software that is specifically tailored to their needs. BA 1306 Spring 2007 Acquiring Software Software is considered to be in the public domain if it is free to all; software in the public domain is sometimes called freeware. Software called shareware is also given away free; the maker hopes for voluntary payment. Copyrighted software costs money and must not be copied without permission from the manufacturer. Making illegal copies of copyrighted software is called software piracy and is punishable under the law. BA 1306 Spring 2007