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.

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 you make to the Inter

net. WWW-http

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?)

• how we make connection http:// ftp:// telnet://

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 click-properties • 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, specif

ic, search facilities• being found when creating a site: query wor

ds 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-of-line 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 savin

g• ASCII and Unicode• show/hide on toolbar for structure of layo

ut• sections, margins in page setup• headers and footers, make tables, help o

ption (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.opera-australia.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 comma-delimited 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.

• 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 printed10 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

Data representation

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 unit-decode

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, flo

ppy disk, tapes, zip, CD ROM, DVD)• Moving data around - buses, ports, expansion sl

ots, scsi drives• Buying a computer - what will you do with it? Co

st – 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

• 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

Node NodeNodeNodeNode

Bus

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

• A modem is needed to connect a computer to a phone line

Communication á la Modem

• The computercommunicateswith digital signals

• The telephone systemwas designed to transmit voice signals, which are analog

aa

Terminal

Modem

Modem

Analogsignals

Phone line

Digitalsignals

Digitalsignals

Computer

The word modem comes from theterms modulation and demodulation

How a Modem Works

ModulationDemodulation

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

Communication á la Modem

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 step-by-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 instance of the given problem

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 viewThe datasheet view shows you the information that is produced when the query is run.

3.SQL viewThis 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 squa

re 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 character1#3 would match 103, 113, 123, 133, but not 1A3.

Sorting

• Sorting on one fieldThree 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 scaleRepresented 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 largeThe 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.

Queryaction queriesThere are four types of action queries:

deleteupdateappendmake-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

B2CBusiness 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