Download Internet - Angelfire

Internet
• Wendy G Lehnert, “Internet 101, A
Beginners Guide to the Internet and the
World Wide Web”,Addison-Wesley, 1998
• The Internet is simply a network of
computers, linked together all over the
world. A “network of networks”.
• size, history
• http://www.isoc.org/internet-history/ brief.html
• Ownership, no rules
• “membership” by connecting to an ISP
• Packet-switching model (origin,
destination, file name, packet number)
• LAN or WAN
• Every network has a IP address (URLs)
• Protocol://host computer/path/filename
• major domain name
edu,com,org,net,gov
• country code au uk
• Protocol defines the type of connection
Protocols
• A set of rules for communicating the end
points in a telecommunication network use
when they send signals back and forth
• regardless of computer type
• need internet connection, appropriate
software
• IP-internet protocol, TCP/IP-transmission
control protocol, HTTP-hypertext transfer
protocol, SMTP-simple mail transfer protocol,
FTP-file transfer protocol, telnet, (video
protocol?)
Caches and proxy servers
• The cache is simply a temporary
storage area where your browser stores
files that it downloads. Using BACK
button.
• In Internet Explorer: temporary internet
files under windows folder
• Proxy server - cache provided by ISP,
invisible to user, intermediary between
user and Internet, filters requirements,
looks at local cache, requests server on
Internet on behalf of user
Firewalls
• In computer networks used to control the
material that passes between a network
and the outside world. Mixture of hardware
and software that acts as a buffer between
your network and the rest of the Internet.
The firewall controls access into and out of
your network.
Web Pages
• Web page uses hypertext markup
language view-page source
• home page (start of the book)
• Frames - designated sections of a page
with different source, URL: right clickproperties
• internet address - address of network
• e-mail address - address of account
• web page address - address of file
Searching the Web
• Search Engine is a Web page which has
been set up to allow you free web
searching and support service.
• Altavista: Advertising, find good content
• search engine use a spider or crawler
which work its way around the Web from
link to link, collecting data to create a
database.
• Spider/crawler, a database, software query
Searching
• Spider captures references to many web
pages
• out of date, moved location, account
expired
• syntax use on queries “…..”, multiple
words, comput*, be specific, and/or/not, + • hitlist, directory search engines (index of
categories ), key word search engines
Favourites
•
•
•
•
•
Internet Explorer- Favorites
Netscape Communicator- Bookmark
URL and title, housekeeping
use official sites
referencingbooks: title, author, publication
details, page number
• referencing Web pages: URL, author, date
found
• Search within page:edit-find, search
button
• evaluating search engines: database,
specific, search facilities
• being found when creating a site: query
words in title or start, close together,
many instances of query words, list of
search engines, requirements, let them
know, include links
• http://www.albany.edu/library/internet/second.
html
Word Processing (2)
• Document (.doc) has content ( text, graphics, charts)
and form (appearance).
• “This is a text file “Text.txt contains 21 characters
(the 19 characters that we wrote, plus an end-ofline character and an end-of-file character),
Word.doc contains 19456 characters! RTF contains
2582 characters.
• RTF (Rich Text Format) it is a file format that allows
you to exchange document files in text format
between different versions of the same word
processing software, Different word processing
software packages, Different operating systems.
Word Processing (3)
• Save, Save As, Autosave
• .tmp file keeps new changes before
saving
• ASCII and Unicode
• show/hide on toolbar for structure of
layout
• sections, margins in page setup
• headers and footers, make tables,
help option (contents-index).
Word
• RAM (random access memory) and
ROM( read only memory) with documents
• Clipboard - temporary memory space
• copy-paste
cut-paste
• Deleting, Undo, Redo button
• Find ( can use * ? ) and Replace
• Insert-symbols (special characters)
• Clip Art and WordArt
Tools in Word
• Spell checkers: language, technical and
proper names, grammar errors of context,
use of add button,
• Grammar Checker - Auto Correct Thesaurus
• Properties of files to see statistics
HTML
• HTML is the language that most Web
browsers use.
• We say that most web pages are coded in
HTML
HTML and Web Browsers
• In this case, the "compiler" or document
handler is your Web browser (Internet
Explorer or Netscape) which is designed
to handle text documents encoded with
HTML tags.
How to start HTML
•
•
•
•
•
•
•
•
<html>
<head>
<title>First Marked up Document</title>
</head>
<body>
…………
</body>
</html>
Backgrounds
• <body background="htmlbg.gif"
bgcolor="#ffffcc" link=#ff7777
text=#cccccc>
• Declares background and default colours
of background, text, and links in the web
page.
Headings
• the beginning and end tags are identical except
for the forward slash (/)
• <H1>Make your own Heading</H1>
• <h2> smaller
• <h3> and smaller
• <h4> and smaller
• <h5> and smaller
• and
• <h6> smallest
Formatting text
• <font color="#FF0000"><font
size=+2> ………….. </font></font>
• <b><u><i> comp123 </i></u></b>
• <hr WIDTH="100%"> draws a line
• <center> </center> centres text
• <br> and <p> line spaces
Images
• <img SRC="Aobo.gif" height=118
width=350>
• Make sure picture is in same folder as web
page (html file)
• The tag <img> has a number of attributes
including "width", "height", "align“.
Links
• <a href="http://www.operaaustralia.org.au/”>link to opera page</a>
• <a href=“page1.html”>link to Web Page
1</a>
• <a href =“#Top”> go to top of page</a>
Lists
• <li>............list item(puts a "dot" before
each item)
<ul>............unnumbered list
<ol>............ordered list (numbers each
item)
• <ul>…</ul> or <ol>…</ol>
• <li>item 1</li>
• <li>item 2</li>
Tables
•
•
•
•
•
•
•
•
•
<table> .... </table> define a table
<th> specifies table heading
<tr> specifies rows in a table
<td> ... </td> define data contained in a cell
<table border=4 width=100%>
<th>Heading1</th><th>Head Cell 2</th><tr>
<td>Cell 3</td><td>Cell 4</td><tr>
<td>Cell 5</td><td>Cell 6</td>
</table>
toolbars
• Picture - controls a selected image. You can use this to
adjust the brightness or contrast of an image, or carry
out other functions.
• Office Clipboard - It used to be a fact that the clipboard
could only hold one thing at a time. Using the Office
Clipboard, as outlined in the text, allows you to store up
to 12 different items on the Clipboard at once.
• Tables and Borders - This can be used as another way
of controlling the tables in your document; you don't
have to go to the Table menu.
Fonts
• Scaleable Fonts:can be adjusted to any
size, and can be printed well on any
printer that prints graphics.
• Printer fonts are fonts that are built into
the printer. True type or postcript fonts
• Screen Fonts: In order to display a font
on your screen, the font type and size
must be installed in your computer.
Screen fonts are bitmapped fonts.
• Lists : ordered or unordered, flat or multilevel.
An ordered list would be used when whatever
is being listed should be numbered while an
unordered list may be used for a list of related
items which could appear in any order.
• A normal list is flat, only one level, but it is
possible to have a multilevel list (Outline
Numbered List).
•
Mammals
•
•
•
•
•
Dogs
Labrador
Poodle
Horses
Dolphins
Paragraphs
• “is any amount of text, graphics, objects or
other items that are followed by a
paragraph mark” (¶)
• You insert a paragraph mark each time
you press “Enter”
• Wrap around - word wrap
Widow and Orphan
Control
• Widow: the last line of a paragraph printed by
itself at the top of a page
• Orphan: the first line of a paragraph printed by
itself at the bottom of a page
• Keeping lines together
Hyphenation
• Allows more text to fit on a line
• Improves appearance
• Often used with full justification
(e.g. newspaper columns)
• In Word can choose automatic or manual
Headers and Footers
• Puts vital information on each page
• Can be text, drawing, page number, date,
file name etc
• Need to use sections to have different
headers and footers (as in assignment)
• Worth getting to know
• Logos
• First page
Templates
• Master copy for all documents of a certain
type
• Can include text and graphics
• Sets margins and document formats
Normal.dot
• Times New Roman
• 12 pt
(in Word 2000)
• Left aligned
• Single spacing
• ….
Customised Templates
• Saved as .dot files
• Easiest way to make a template:
Open a document that has the formatting
you want, and save it as a template
• Task for you
Hidden text
• Hides notes and comments in a document
• Options
– Can be seen on screen (or not)
– Can be printed (or not)
• Warning - be careful how you use it!
Mail Merge
• Mail Merge can be used to merge any kind of
data with any other kind of document to
individualise the documents.
• create a mail merge, need the data document
and the merge document. The data document
needs to be a tab-delimited or commadelimited text file, which is simply a file with
repeating fields that are separated
("delimited") by a tab character or a comma.
Set up in MS Word, MS Access, MS Excel, or
Outlook.
Data representation
• Bits (smallest unit of information)
1 bit = 0 or 1
• Byte (8 bits)
1 byte: A single character
• Kilobyte (approximately 1000 bytes)
1 Kilobyte: A very short story
2 Kilobytes: A Typewritten page
• Megabyte (approximately 1 000 000 bytes)
1 Megabyte: A small novel
5 Megabytes: The complete works of Shakespeare
100 Megabytes: 1 metre of shelved books
650 Megabytes: A CD-ROM
Data representation
• Gigabyte (approximately 1 000 000 000 bytes)
1 Gigabyte: A pickup truck (eg. Ford F250) with cargo area filled with
printed paper to a depth of 40 cm.
20 Gigabytes: A good collection of the works of Beethoven
100 Gigabytes: A floor of academic journals
• Terabyte (approximately 1 000 000 000 000 bytes)
1 Terabyte: 50, 000 trees made into paper and printed
10 Terabytes: The printed collection of the US Library of Congress
• Petabyte (approximately 1 000 000 000 000 000 bytes)
2 Petabytes: All US academic research libraries
200 Petabytes: All printed material
• Exabyte (approximately 1 000 000 000 000 000 000 bytes)
5 Exabytes: All words ever spoken by human beings.
• How many bits / bytes in a floppy disk / CD-ROM /
in 10 GB?
• Conversion of binary to decimal
Representation standards
•
•
•
•
•
•
ASC II and Unicode
Conversion of characters, numbers and symbols
to binary numbers
A = 100000001 B = 10000010 (1 byte)
ASC II limited to 256 (28) different variations or
characters
A = 1000000000000001 (2 bytes)
Unicode limit is 65000 different variations
Memory, CPU
•
•
•
•
•
•
•
•
•
•
RAM - random access memory
volatile, temporary, fast access
ROM - read only memory
non-volatile, permanent, slow access, CACHE
The processor is called the CPU central processing unit
compatibility, speed, RISC (reduced instruction set computer) IBM for Macs faster
CISC (complex instruction set computer) - Intel for Pentiums
slower
Fetch instruction - Memory - Bus interface unit - pre fetch unitdecode unit- control unit- ALU arithmetic logic unit (registers of
32 and 64 bits)-sent back to memory
Machine cycle: instruction set is read - write - move –operate on
data- make decisions
Algorithm that repeats forever: fetch instruction – increment
program counter – decode instruction – obey instruction
Hardware
• Buses (travel between components of the
computer in 8, 16, 32 bits)
• Ports (serial and parallel)
• Peripherals - input, output, storage (hard disk,
floppy disk, tapes, zip, CD ROM, DVD)
• Moving data around - buses, ports, expansion
slots, scsi drives
• Buying a computer - what will you do with it?
Cost – software- expansion
Software
• Software: compilers software applications,
system software
• Compilers and translators - translate
programs to machine language
• Programming languages - C++ Java Basic
• How CPU executes a program (adding
2numbers):
• get (read) number at memory location x and
place in register A, get another number, add
contents of registers and put in register C,
write (copy) register C to memory location y.
Programs
• Integrated software: cheaper, transfer of
data easier, feels and looks same
• Public domain software, shareware,
freeware
• Proprietary software–licence(allowed to
use the program,still property of the
company)
• piracy
System Software
• Taking care of hardware issues relating to what you are doing in
software
• Operating systems: keeps hardware running efficiently, makes
process of commun9icating with the hardware easier
• communicate with peripherals, coordinates concurrent processing of
jobs (multitasking), manages the memory, data and program
management, monitors resources, accounting and security,
coordinates network communications.
• Multitasking is when the computer seems to be working on several
programs at the same time (speed).
• Utility software: tools for doing system maintenance and some
repairs the OS can’t automatically handle.
• Virus scan, fix corrupted data files
Operating System
• MS-DOS, Macintosh, Microsoft Windows
• User Interface- software (application) program operating system (hardware)
• Software compatibility (RTF) and reliability
• OS lives in ROM and starts up computer with
“booting” process.
• Character based and Graphical User Interfaces
(GUIs) – (advantages of GUIs) intuitive,
consistent, forgiving, protective, flexible.
Bandwidth
• bandwidth - amount of information cable can
hold (allow to travel on it)
• ISDN -integrated services digital network - callup
digital line with 128Kbps
• T1 and T3 direct digital with 1.5-3Mbps
• Intranet – a small copy of internet at work inside
the LAN/WAN network of a company.
• Extranet – a private network between company
and business clients
Linking Up: Network Basics
• Why is networking important?
– Cost
• allows people to share hardware
– Efficiency & Productivity
• allows people to share data and software
– Opportunity
• allows people to work together in ways that are
otherwise difficult or impossible
LAN (Local Area Network)
• Network of interconnected workstations
• Sharing common resources
• Within a relatively small geographic area
Client-Server LAN
• Server
– Storehouse for software and data
– Management of shared resources
• Printers
• Client
– Computers that request server services
Peer-to-Peer LAN
• There are no servers
• Shared resources managed by all
computers
• Effective for small LANs
LAN Architecture
• Almost all LANs are set up as one of
– Star
– Ring
– Bus
Bus
Bus
Node
Node
Node
Node
Node
• Every node is connected to the bus
• All communication travels along the bus
• Only one node can send information along the bus
at a time
• Ethernet uses this model
MAN, WAN
• Networks that extend over a long
distance
– MAN: Metropolitan Area Network
– WAN: Wide Area Network
• Usually composed of smaller MAN / LANs
WAN (Wide Area Network)
WANs are often made up of LANs
Differences between LANS and
WANs
• LANs small geographic area
– WANs large
• LANs almost always controlled by single
organisation
– WANs usually aren’t
• LANs have a regular structure
– WANs don’t
The Network Interface
• A Network Interface Card (NIC):
– Is needed to connect directly to a network
– Adds an additional port to the computer
– Controls the flow of data between the
computer’s RAM and the network cable
– Converts the computer’s digital signals into
the type required for the particular network
Modem
• Modulator/demodulator
• Connects a computer to a telephone
line
• Connection speed: Kbps
Communication á la Modem
• A modem is needed to connect a
computer to a phone line
• The computer
communicates
with digital signals
• The telephone system
was designed to transmit voice signals,
which are analog
How a Modem Works
The word modem comes from the
terms modulation and demodulation
Modulation
Demodulation
Communication á la Modem
A modem:
– Converts the digital stream of information
from a computer to an analog stream in
order to send a message on the telephone
network
Communication á la Modem
A modem:
– Converts the analog stream of information
received over the telephone network into the
digital form that the computer understands
Building Bandwidth
• The quality of information transmitted
through a communication medium
depends upon bandwidth.
– Increased bandwidth means faster
transmission speed
– Bandwidth is affected by the amount of
network traffic, software protocols, and type of
network connection
Intranet
• An intranet is a private network that is
contained within an enterprise
• Uses same technology as the Internet
• Typically connected to the internet by a
firewall for security
Extranet
• Private Internet-like network designed
for outside use (E-Commerce)
• An extranet can be viewed as part of a
company's intranet that is extended to
users outside the company
What is an algorithm?
• Problem instance is an assignment of
values to parameters
• Algorithm for a problem is a general stepby-step method taking any problem
instance and giving a correct answer for
the instance
• Algorithm is correct (for a problem) if it
gives the correct answer for every
Characteristics of Algorithms
• Algorithm: sequence of steps to
accomplish a task
– must produce output in all cases
– must terminate in all cases
– must produce correct results in all cases
– must be effective(each step is doable)
– must be definite (specific course of action for
every eventuality)
Algorithms vs. Programs
• Aren’t they the same thing?
– Computer can only perform tasks specified by
simple operations it can execute
– We need to describe how the task can be
completed; which operations to perform
– This description is known as an algorithm
– A program is an algorithm that can be directly
executed by a computer
Selecting the Appropriate Chart
• Bar and column charts
– emphasize variations between items over time
– use when data falls into a few categories
• Line chart
– show trends in data over time
– show relationship of one variable to another
• Pie chart
– show proportion of parts to a whole
• XY (scatter) chart
– used more often to discover relationships between
data
Record Macro
• to automate often repeated tasks
•
•
•
•
Tools/Macro/Record New Macro
Macro name box - name for macro
Shortcut key
Description box - what macro does
Record Macro
• Click stop record button
Record Macro : Example
Sort or filter macros
• Highlight spreadsheet
• Data sort:
• Data filter autofilter  custom
Run a macro
• Tools/macro/select name - as
previous e.g.
• Shortcut key combination
• Assign macro to button/graphic &
click
Adding Buttons
•
•
•
•
Forms toolbar/Button Tool
Active cell - location of button
Drag to desired size & shape
Assign macro dialog displayed
Representation in spreadsheets
• Data consists of numbers or text
• Numeric data is real:
– dates, currency, percentages are stored as real
numbers
Query
• Queries are used either to ask questions about
the data in a database, or to specify those parts
of a database for which data is to be changed in
some way
• Choose the fields in a table that you wish to
display
• Select on a certain set of the records in a table
• Show the selected material in some particular
sequence
• Derive the data that is to be shown from a
number of tables in the database
• Calculate totals
Queries
• Access provides 2 ways to specify
queries:
• QBE approach (Query By Example) - a
graphical interface that allows you to
design your query in a fairly intuitive
manner.
• SQL (Structured Query Language)
• If you choose to use QBE to develop
your query, you can have a look at the
SQL view and see what SQL the query
you design produces.
• Three views for a query:
1.Design view
This lets you see the rules by which the
query is constructed. It will show the
table(s) used, the fields that have been
selected, and any constraints (criteria)
used to select particular records from
the table(s).
2.Datasheet view
The datasheet view shows you the
information that is produced when the
query is run.
3.SQL view
This view shows the SQL query that is
generated from the graphical
specification
Types of queries
• Select queries:
The purpose of a select query is to extract
and present information from the
database. The way in which we specify
what is to be selected and presented is by
establishing criteria.
• Action queries:
Action queries are used either to make
new tables in a database, or to alter in
some way the data (make table,
delete,update,append).
QBE
• Query by example, we select the fields
that we wish to incorporate in the query
by:
• First selecting the table(s) that we need to
provide the required output
• Then selecting (in the order (left to right)
that you wish the data to be presented)
the fields you need.
QBE
• Criteria are restrictions you place on a
query to identify the specific records you
wish to work with.
• Criteria: 2124
• Use Null, And Or Not, Between
• Null is defined as nothing - an empty or
zero length string.
• Is Not Null (has a value in the field)
• <> 0 (not equal to 0)
And / Or
• And in QBE (>= 15 And <= 18)
• Field: WinbCommbWordbSsheetb
• Criteria:"O“ "E“
"E“
"E“
• Or
• Tu2p Or Tu3p
• Criteria:
Tu2p
• Or:
Tu3p
Wild Cards
•
•
•
•
* (anything after or before *)
Tu* (anything that starts with Tu).
*p (anything that ends with p).
? - Matches any single alphabetic
character (categori?e)
• [] - Matches any single character
within the brackets (c[au]t)
• ! - matches any character that is not
specified in the square brackets
• b[!ae]ll finds bill and bull but not ball
or bell
Wild Cards
• - - Matches a range of characters. The
range is in ascending order (A - Z).
a[a-d]x will match aax, abx, acx, adx
• # - Matches a single numeric
character
1#3 would match 103, 113, 123, 133, but
not 1A3.
Sorting
• Sorting on one field
Three options are available for the
sequence in which any field appears:
• Ascending sequence
• Descending sequence
• Not sorted
• The field that you choose to sort over may
be text, numeric or date
Show field option
• The Show line on the QBE grid
contains a Tick box for every field
that is used in the query. When the
box is crossed, the field is shown; if
it is not, it is not visible when the
query is viewed in datasheet view.
Saving queries
• All query names start with Qry
• Update queries start with Qry
Update
• Append queries start with Qry
Append
• Name queries when you close the
datasheet view of query
Multi-table queries
• Much of the power of querying tables
in a relational database is the ability
to bring together data from multiple
tables.
Basics
• Graphics are represented by pixels
(640x480, 800x600, 1024x768,
1280x960 screen sizes)
• Quality of graphics is determined by:
– Resolution of the screen (dpi)
– Number of colors
• Determined by hardware and software
Forms of Graphics
• Bit mapped (raster graphics)
• Objects (vector graphics)
Black and White
• Grey scale
Represented as 1 byte per pixel
• 256 shades – more than naked eye can
distinguish
• See demo at:
http://www.aa6g.org/Astronomy
/Articles/grayscale.html
Grayscale
Colour implementation
• 1 byte gives 256 colours
• 2 bytes gives 65536 colours
• Tradeoff between resolution and storage
requirement
Dithering
Dithering is the attempt by a computer program to
approximate a colour from a mixture of other
colours when the required colour is not available.
For example, dithering occurs when a colour is
specified for a Web page that a browser on a
particular operating system can't support.
Browser Safe Palette
216-Color Browser-Safe Palette
When specifying colors for Web page backgrounds,
fonts, and other elements for 256-color displays
(the most common display capability), you will
probably want to choose from the 216 colors that
look the same on both PC and Mac operating
system
Compression
Graphics files are large
The COMP123 logo is 472 x 81 pixels
(38232 bytes) It is compressed to 23019
bytes
Compression is the reduction in size of
data in order to save space or
transmission time.
Forms of compression
• Lossless – e.g Winzip
• Lossy – e.g. jpeg
JPEG
• A JPEG (pronounced JAY-peg) is a graphic
image created by choosing from a range of
compression qualities (actually, from one of a
suite of compression algorithm). When you
create a JPEG or convert an image from another
format to a JPEG, you are asked to specify the
quality of image you want.
GIF
On the Web and elsewhere on the Internet,
the GIF has become a de facto standard
form of image.
The LZW compression algorithm used in the
GIF format is owned by Unisys replaced
by PNG (which is free)
GIF uses up more space.
Sound
• Measured by sampling
• Uses lots of space
• Quality is a function of
– Sampling rate
(Telephone line is 33KHz; )
– Bit rate
(Twice the bandwidth (Nyquist theory))
Video
• Combines pictures and sound
• Uses huge amounts of storage
Hypermedia
Combination of text, numbers, graphics,
sound, music, video, virtual reality and
other media in hyperlinked documents
Bandwidth
Bandwidth is directly proportional to the
amount of data transmitted or received per
unit time
(measure of the range of frequencies the
signal occupies)
Summary queries
• Do not change the data in the database
• Produce total information
• View totals
• Created by using the  tab
• Can combine the options
Action queries
An action query is a query that makes changes to
many records in just one operation.
Queryaction queries
There are four types of action queries:
delete
update
append
make-table
Delete query
• Delete query
– Deletes a group of records from one or more
tables.
Update queries
• Example:
– Update the results for the Winb Basic
assignment
• First – be quite clear about the rules.
Append query
• Adds a group of records from one or more
tables to the end of one or more tables
• Example:
– Add new students to Studdetails
Make Table
• Creates a new table from all or part of the
data in one or more tables
• Used for:
– Creating a history table that contains old
records
– Creating a table to export to other Microsoft
Access databases
– Taking a snapshot of a table
The expression we use:
• Value:[UnitPrice] * [Quantity]
• What do the square brackets mean?
• Existing fields
• New price: [price]*1.1
SQL – Structured Query
Language
• Each query that you create produces an
SQL version
• You can check this – there are three views
of a query:
– Datasheet
– Design
– SQL
What is Electronic Commerce?
Electronic Commerce is the term used when
commercial transactions take place across
the Internet or another private network
without human intervention
Business to Business
Transactions
• Most common form of E-Commerce
• Used in:
– Manufacturing
– Sales
• Allows for Just-In-Time manufacturing
EDI (Electronic Data
Interchange)
• EDI refers to the exchange of electronic
business documents
(no human intervention)
• EDI standards
• Agreement between 2 organisations
B2C
Business to Customer
• Growing area
• Some successes, lots of failures
• Must be built into the business model
Internet banking
•
•
•
•
Faster
Cheaper
More flexible
Not time dependent
Web based retailing
•
•
•
•
Business to Customer
The issues
Is it working?
Amazon has never made a profit for a
whole year
• What sort of products sell?
Advertising, Marketing
• The 4 Ps of Internet marketing
– Product
– Price
– Place (Distribution)
– Promotion
Security Issues
• 1.
Confidentiality
– Privacy of message (encryption)
• 2.
Integrity
– Detecting message tampering(Hashing)
• 3.
Non-repudiation
– Provision of irrefutable evidence of origin,
receipt and contents (Digital signatures etc)
Cont ..
• 4.
Authentication
– Is the sender who he/she claims to be?
(Digital signature, password etc)
• 5.
Authorization
– Access control (limiting entry to authorized
users) (Firewalls, passwords etc)
What is Cryptography?
• Cryptography is a means of mathematical
encoding that converts messages into a
form that is unreadable, in an effort to
maintain confidentiality of data.
Public key cryptography
• There are two keys, public key, private key
• Public keys are published
• Private keys are kept secret
(you keep your own private key)
Sending a message:A to B
• Adam encrypts the message using Beth’s
public key
• Beth decrypts the message using her
private key
• Anyone can send you a message
• Only you can decode it
• How does the recipient know who really
sent the message?
What is a system?
• A system is much more than the software that is
used.
• System incorporates
–
–
–
–
–
–
the software
the training of users
installation plan
user documentation
maintenance plan
…….
Software Development Life
Cycle
•
•
•
•
•
•
Requirements analysis
Design
Implementation
Testing
Installation
Maintenance
Systems Development Life
Cycle (1)
• First catch your problem
(the hardest bit it to get this right)
• Understand how the problem fits into the
organisation’s overall scheme of things
Systems DLC (2)
• Design a solution that fits into the
organisation
• Develop the system as a whole
–
–
–
–
–
–
–
–
Software
Testing
Training
Systems documentation
User documentation
Installation plan
Maintenance plan
Plan for obsolescence
Systems DLC (3)
• Systems Installation
• Systems maintenance
(about 60-70% of the cost of a system is
spent after the syetem is installed)
What is a VIRUS?
• A virus is
–
–
–
–
code
inserted into a program
cause some unexpected/undesirable result
replicates itself
What should I do?
•
•
•
•
•
Install Anti-virus Software
Use a legal copy - why?
E-mail
Downloads
Floppies
How does Anti-Virus
Software Work?
• Signatures built in to the infected file
• The anti-virus trail
–
–
–
–
–
Collect suspicious files
Identify similar cases
Work out what the virus does
Develop antivenene
Add to repertoire
Boot Sector Virus
• Boot sector
– floppy disk
– hard disk
• Effect?
File Infector Virus
• Attaches itself to program files
– .COM
– .EXE
• The effect?
Macro Virus
• Typically Word or Excel
• Effect - often inserts rubbish
• Note the warning in Outlook!
Trojan Horse
• Program that is expected to do one
thing and does another
• Password capture
Worms
• Self-contained program
• Spreads functional copies of itself
• Does not attach to a host program
• Two types
– Host worm
– Internet worm
What is Artificial Intelligence?
• AI is the study of ideas which enable computers
to do the things that make people seem
intelligent (Winston).
• AI is the study of how to make computers do
things which at the moment people are better at
(Rich)
• AI is the study of the computations that make it
possible to reason, perceive, and act (Winston).
How do you tell if a
computer is intelligent?
• Turing test (1950)
• A machine can be deemed intelligent when it
can pass for a human being in a blind test.
• (computer, human) answer questions from
human….depending on answers human must
determine which answer came from a
machine…if fooled then computer deemed
intelligent.
• No computer has passed test.
Natural Language Processing
•
•
•
•
•
•
Speech recognition
Language understanding
Translation
Language generation
Text to speech synthesis
Problem
–
–
–
–
–
Syntax
Semantics
Syntactical ambiguity
Semantic ambiguity
Fluidity of language
Expert Systems
• A software program designed to
replicate the decision making process of
a human expert.
• Examples
– Bank loans
– Credit card applications
– Medicine - diagnosis systems
– Design - Xerox paper handling systems
– Farming - CSIRO