ACKNOWLEDGEMENTSACKNOWLEDGEMENTSACKNOWLEDGEMENTSACKNOWLEDGEMENTS

I have grate pleasure in expressing my heartiest thanks to the who have

helped me submit this project first and fore most I would like

acknowledgements with pleasure Mr.S.Seelan, Computer Co-ordinator and

lecture in NAITA. I am grateful to Mr.S.Pavalanathan, present NAITA

chairmen who also help me.

I have to also personally thankful to Mr.S.Seelan, lecture NAITA

Computer Training Center and supervisor for this project report for valuable

ideas, recommendations and supports, he whice have added quality to this

project.

I am also especially thank our public library in Vavuniya and I take this

opportunity offering my grateful thank to all my friends and colleagues and my

family members who have been grate help to me personally prepare this

project.

Once again I thank to you all.

............................................

(A.KOGULAN)

CONTENTSCONTENTSCONTENTSCONTENTS

Chapters Page

Chapter 01

Introduction to computer 001

What is Information Technology? 002

Father of computer 004

Computer or a pc 005

Computers in human lives 007

A complete computer system 009

Age of computers 010

Classification of Computers 012

The Five Generations of Computers 018

Computer Generations briefly Explanation 021

Artificial intelligence 029

Main Circuit Board of a PC 030

History of the Motherboard 036

Programming Languages 040

Intel Processors: Now and Then 044

Chapter 02

The Components of a Computer 053

Input Devices 058

Output Devices 069

CPU (Central Processing Unit) 076

How computers work? 079

Booting Process 080

Operating system 082

Chapter 03

System Software 090

Application Software 095

Chapter 04

Introduction to Computer Viruses 099

Installing Anti-virus Software 110

Chapter 05

Primary Storage 122

Secondary Storage 128

Chapter 06

Networks 137

Internet & WWW 172

The Number Systems 217

Characters and decimal, binary, ASCII, EBCDIC Value

Capital Letters 220

Small Letters 221

Shortcut Keys 222

What is DOS? 226

DOS commands and explanation 228

Modem error messages 232

Abbreviation 240

INTRODUCTION TO COMPUTERINTRODUCTION TO COMPUTERINTRODUCTION TO COMPUTERINTRODUCTION TO COMPUTER

We might be aware of the fact that the computer is affecting our lives in

many ways. Almost everyday we hear about the newest ways that a computer is

being used for. So why not to Call it a Computer Revolution. Computers have

now become an important part of our lives with all these rapid development

taking place.

Till now you might have been using a typewriter for drafting your

commercial correspondence a calculator for performing lengthy calculations

and files for maintaining records. Now we can do all our correspondence,

calculation and record main fence on a computer at a much faster speed.

Besides facilitating the office work. Computers today are also paying a

significant role in the fields of education and entertainment. As the use of

computers steadily increases, so does the need for batter understanding of its

functions.

WHAT IS INFORMATION TECHNOLOGY?WHAT IS INFORMATION TECHNOLOGY?WHAT IS INFORMATION TECHNOLOGY?WHAT IS INFORMATION TECHNOLOGY?

IT (information technology) is a term that encompasses all forms of

technology used to create, store, exchange, and use information in its various

forms (business data, voice conversations, still images, motion pictures,

multimedia presentations, and other forms, including those not yet conceived).

It's a convenient term for including both telephony and computer technology in

the same word. It is the technology that is driving what has often been called

"the information revolution."

Data and Information

Data is a collection of raw unprocessed facts, figures, and symbols.

Computers process data to create information. Information is data that is

organized, meaningful, and useful. Computer processes several data items to

produce a paycheck. Another example of information is a grade report, which

is generated from data items such as a student name, course names, and course

grades.

A user is someone who communicates with a computer or uses the

information it generates.

Hardware is the electric, electronic, and mechanical equipment that

makes up a computer. Software is the series of instructions that tells the

hardware how to per form tasks. Without software, most hardware is useless.

The hardware needs instructions from software to process data into

information.

Data

(1) In computing, data is information that has been translated into a form

that is more convenient to move or process. Relative to today's computers and

transmission media, data is information converted into binary digital form.

(2) In computer component interconnection and network

communication, data is often distinguished from "control information,"

"control bits," and similar terms to identify the main content of a transmission

unit.

(3) In telecommunications, data sometimes means digital-encoded

information to distinguish it from analog-encoded information such as

conventional telephone voice calls. In general, "analog" or voice transmission

requires a dedicated continual connection for the duration of a related series of

transmissions. Data transmission can often be sent with intermittent

connections in packets that arrive in piecemeal fashion.

(4) Generally and in science, data is a gathered body of facts. Some

authorities and publishers, cognizant of the word's Latin origin and as the plural

form of "datum," use plural verb forms with "data". Others take the view that

since "datum" is rarely used, it is more natural to treat "data" as a singular

form.

Information

Information is stimuli that have meaning in some context for its

receiver. When information is entered into and stored in a computer, it is

generally referred to as data. After processing (such as formatting and

printing), output data can again be perceived as information. Data will be

converted in to Information after processing.

When information is packaged or used for understanding or doing

something, it is known as knowledge.

FAFAFAFATHER OF COMPUTERTHER OF COMPUTERTHER OF COMPUTERTHER OF COMPUTER

Charles Babbage was intrigued by the problem of errors in the hand

calculation of complex mathematical tables. He was inspired by Charles

Mohan’s logic machine which he used as a starting point

and a working difference engine was completed in1822

and was used to calculate simple tables in 1833

Babbage abandoned the project and began

work on his real dream, the “Analytical

Engine”, a general purpose machine that

would be capable of performing any type of

digital calculation. Although his analytical

engine was never built Babbage did succeed in

mapping out all the principles and procedures from which all

modern digital computers have followed. As a result he is considered to be the

source of the automatic computer.

COMPUTER OR A PCCOMPUTER OR A PCCOMPUTER OR A PCCOMPUTER OR A PC

For layman, a PC or a Computer is like a super calculator with a really

big display computer is perhaps the most useful tool ever invented. In technical

terms, computer can be defined as an electronic device that accepts data,

processes information in a pre – defined Fashion, according to the set of

instructions provided to it and produces the desired output.

The term PC, it is self explanatory. PC stands for Personal Computer as

it is your own computer you are working upon. This term was adopted by IBM,

the largest manufacturer of computer, to describe its first desk sized computers.

Computers differ in variety and size – from a simple playing computer

like spectrum to large mainframe or super computer like India’s own super

computer frame.

You might be wondering if a computer can store a large amount of data,

then it must have a huge amount of intelligence too. Ironically, the computer’s

intelligence level does not equal to that of a cockroach even. Through, research

is on to impart some intelligence to if of its own. The computer only follows

the instructions given to it by the user. If follows the concept of what you give

is what you get, which means that whatever instructions you give, accordingly

would be the result. A computer Fed with wrong instructions would give you

wrong results.

Super Computer

COMPUTERS IN HUMAN LIVESCOMPUTERS IN HUMAN LIVESCOMPUTERS IN HUMAN LIVESCOMPUTERS IN HUMAN LIVES

The number of ways that computers affect human lives is uncountable.

Computers can perform all those functions that a human being can do to a

certain extent, but at a much faster speed and with greater accuracy.

Computers are used in banks to take care of the accounting system and

keep track of the enormous amount of money. Although all these tasks are done

manually also, but it takes as great deal of time. If it takes about a month to

make the balance sheet, a computer can make it in a few hours. Computers help

you perform tasks like account handling; taking out complex reports, balance

sheets, etc in a much shorten span and the results would also be very accurate.

Let us take an example that you have an account in a bank which is fully

computerized throughout the country. You leave an account in one of its

branch in Colombo but at present you are in Vavuniya and you wish to encase

a cheque. You need not call up Colombo branch, and confirm your account and

perform other formalities. The cashier at Vavuniya branch of the bank would

check up your bank account number of Colombo on computer and if it is there

and you have the essential amount of money in your account, your cheque will

immediately get encased see how simple it is with a computerized system!

Now let us take up an example of an architect who designs your houses

and buildings. Suppose he has been asked to design a housing complex with

each lat of about 2000 sq.ft. According to the dimensions of the area and the

number of houses required, he would draw the design or layout of that

complex, which could take about a month or so. Let us suppose, he completes

the project and is given another assignment for another housing complex, but

with a greater area of say 2500 sq.ft. Now if the architect starts off with the

drawing it right. From the beginning it would take another month or so. Don’t

you think it consumes too much time? There is a possibility that he could

commit some mistakes which will head to redoing of the same job. A computer

can provide a great deal of help in this context also If you have a certain

program in your computer that could help you draw the layout according to the

dimensions and many other things you specify the time of drawing could be

reduced to a few hours or even less. More over, if you get a new assignment to

draw the same design with a greater area, you would be able to finish it in

relatively no time, if you have saved the previous assignment, in the computer.

So a computer makes the job much simpler and easier and most of all, the least

time consuming.

These examples are just a fraction of the world-wide trend about the

various jobs that a computer can perform computers are used broadly even in

educational institutions, by doctors, in business for guiding astronauts through

space and much more. We have developed a society that is almost dependent

on computerized system of functioning. So it becomes very essential to have

the basic knowledge of the computer system.

A A A A COMPLETE COMPUTER SYSTEMCOMPLETE COMPUTER SYSTEMCOMPLETE COMPUTER SYSTEMCOMPLETE COMPUTER SYSTEM

The computer system comprises of Hard Ware, Soft Ware, Live Ware and Firm

Ware.

Hard Ware

All the tangible devices which are uses in computerize systems.

Soft Ware

These are the program devices the hard ware and perform different task.

These including operating system like DOS, Productively soft ware like

spooling.

Live Ware

The human involvement for the computer systems. A computer system

like information systems managers, system analysts, programmers etc.

Firm Ware

Firmware is a big program

E.g.:- Boot Strap Program

Total computer systems.

Hard Ware Soft Ware Live Ware Firm Ware

AGE OF COMPUTERSAGE OF COMPUTERSAGE OF COMPUTERSAGE OF COMPUTERS

1946 J.Presper Eckert, John Manchely and a team of so complete the

electronic numerical intergrator and computer (ENIAC). The first large

– scale electronic digital computer weights 50 tons, stands two stories,

and covers 15000 square feet.

1947 Grace Hopper documents the first computer bug, a tread moth in a

cabinet of the Mark II.

1949 Mource Wilkes of England’s Cambridge University builds the first

stored – program Computer.

1950 The first computer of use binary or digital mathematics. [EDVAC]

1951 The University Automatic computer. The first American commercially

Produced this computer.

1953 IBM introduces the first magnetic tape device. The model 726.

1956 The term “Artificial Intelligence” is corned by MC curtly.

1959 Commercial and Business oriented language (COBOL) is created.

1960 The first modern computer generation ends as vacuum tubes punched

cards and machine code give way to 2nd generation transistors magnetic

tape and languages in computer design and operation.

1965 The 3rd generation is developing by tom Kurtz and John Kemeny of

Dortmaith Collage.

1967 The 3rd generation is under way with IC.

1969 The Intel 4004 becomes the first micro processor and paves the way for

the micro computer.

1975 The Cray 1 super computer is introduced as the fastest computer on

earth.

1977 Introduces the Apple II Personal Computer.

1978 VisiCalc, Electronic spread sheet software is created by Don Brick in.

1979 Micro International releases word start a word processing program.

1981 The IBM PC debuts Microsoft’s MS – DOS becomes its standard

operating software.

1983 Lotus 123 takes VisiCalc’s place as the leading spread sheet program

marketed by company founder, Mitch Kaptur windows is presented by

Microsoft.

1985 The C++ programming language is developed.

1990 The advent of parallel processing and greatly increased processing

power make this the year of Artificial Intelligence.

1992 Apples announce “Personal Digital Assistant”.

1993 Intel PC chips; Pentium developed.

2000 Experts predict that computers containing a billion processors will be

technology feasible exceeding the power of the human brain.

CLASSIFICATION OF COMPUTERSCLASSIFICATION OF COMPUTERSCLASSIFICATION OF COMPUTERSCLASSIFICATION OF COMPUTERS

Classification of Computers we can basically divide in to 3 sections. Based on

generation, size and data representation.

Generations: 1 to 5

Generation & Time Period

First Generation 1946 — 1956

Use of vacuum tubes, large, limited memory, jobs execution coordinated

manually, and speed up to 10,000 ips.

Second Generation 1957— 1963

Use of transistors, more reliable, less heat generation, less power requirement,

speed 200,000 - 300,000 ips.

Third Generation 1964 — 1979

• Use of Integrated Circuits (ICS) by printing hundreds and thousands of tiny

transistors on to small silicon chips

• Speed up to 5 Million Instructions Per Second (MIPS)

• Use of operating systems that automated the running of programs &

communications between CPU & peripheral devices.

• Availability of hardware independent programming.

Fourth Generation 1980s

Use of LS1 & VLSI circuits, costs fallen to a very low level, large memory &

storage, speed up to 200 MIPS

Fifth Generation

5 generation computers will be Artificial Intelligence Systems called Al

computers, which simulate the human brain. Expert systems also fall into this

category.

Size: Micro, Mini, Mainframe, Super

Micro Computers

A microcomputer is a complete computer on a smaller scale and is generally a

synonym for the more common term, personal computer or PC, a computer

designed for an individual. A microcomputer contains a microprocessor (a

central processing unit on a microchip), memory in the form of read-only

memory and random access memory, I/O ports and a bus or system of

interconnecting wires, housed in a unit that is usually called a motherboard.

In an ascending hierarchy of general computer sizes, we find:

• An embedded systems programming computer, which is embedded in

something and doesn't support direct human interaction but nevertheless

meets all the other criteria of a microcomputer

• Microcomputer

• Workstation, as used to mean a more powerful personal computer for

special applications

• Minicomputer, now restyled a "mid-range server"

• Mainframe or mainframe computer, which is now usually referred to by its

manufacturers as a "large server"

• Supercomputer, formerly almost a synonym for "Cray supercomputer" but

now meaning a very large server and sometimes including a system of

computers using parallel processing

• A parallel processing system is a system of interconnected computers that

work on the same application together, sharing tasks that can be performed

concurrently

Mini Computers

A minicomputer, a term no longer much used, is a computer of a size

intermediate between a microcomputer and a mainframe. Typically,

minicomputers have been stand-alone computers (computer systems with

attached terminals and other devices) sold to small and mid-size businesses for

general business applications and to large enterprises for department-level

operations. In recent years, the minicomputer has evolved into the "mid-range

server" and is part of a network. IBM's AS/400e is a good example.

Mainframes

Mainframe is an industry term for a large computer, typically manufactured by

a large company such as IBM for the commercial applications of Fortune 1000

businesses and other large-scale computing purposes. Historically, a mainframe

is associated with centralized rather than distributed computing. Today, IBM

refers to its larger processors as large servers and emphasizes that they can be

used to serve distributed users and smaller servers in a computing network.

Super Computers

A supercomputer is a computer that performs at or near the currently highest

operational rate for computers. A supercomputer is typically used for scientific

and engineering applications that must handle very large databases or do a

great amount of computation (or both). At any given time, there are usually a

few well-publicized supercomputers that operate at the very latest and always

incredible speeds. The term is also sometimes applied to far slower (but still

impressively fast) computers.

Most supercomputers are really multiple computers that perform parallel

processing.

In general, there are two parallel processing approaches: symmetric

multiprocessing (SMP) and massively parallel processing (MPP).

Perhaps the best-known builder of supercomputers has been Cray Research,

now a part of Silicon Graphics. Some supercomputers are at "supercomputer

center," usually university research centers, some of which, in the United

States, are interconnected on an Internet backbone known as vBNS or NSFNet.

This network is the foundation for an evolving network infrastructure known as

the National Technology Grid. Internet2 is a university-led project that is part

of this initiative.

At the high end of supercomputing are computers like IBM's "Blue Pacific,"

announced on October 29, 1998. Built in partnership with Lawrence Livermore

National Laboratory in California. Blue Pacific is reported to operated at 3.9

teraflop (trillion operations per second), 15,000 times faster than the average

personal computer. It consists of 5,800 processors containing a total of 2.6

trillion bytes of memory and interconnected with five miles of cable. It was

built to simulate the physics of a nuclear explosion. IBM is also building an

academic supercomputer for the San Diego Supercomputer Center that will

operate at 1 teraflop. It's based on IBM's RISC System/6000 and the AIX

operating system and will have 1,000 microprocessors with IBM's own

POWER3 chip.

At the lower end of supercomputing, a new trend, called clustering, suggests

more of a build-it-yourself approach to supercomputing. The Beowulf Project

offers guidance on how to "strap together" a number of off-the-shelf personal

computer processors, using Linux operating systems, and interconnecting the

processors with Fast Ethernet. Applications must be written to manage the

parallel processing.

Data Representation: Analog, Digital, Hybrid.

Analog Computer

An analog computer operates in a completely opposite way to the digital

computer.

For a start, all operations in an analog computer are performed in parallel.

Secondly, data are represented in an analog computer as voltages, a very

compact but not necessarily robust form of storage (prone to noise corruption).

A single capacitor (equivalent to the Digital’s computer use of a transistor) in

an analog computer can represent one continuous variable.

The Heath kit Educational Analog Computer is completely self-contained and

contains nine DC operational amplifiers with provision for balancing without

removing problem setup. It also features three initial condition power supplies,

five coefficient potentiometers, four sets of relay contacts, an electronically

regulated power supply and a built-in repetitive oscillator for automatic

operation. The complete EC-1 kit also contains an assortment of precision

resistors, capacitors, special silicon diodes and patch cords for setting up scores

of complex computer problems easily and accurately.

Digital Computer

The digital computer is a sequential device, in general, operating on data one

step at a time; in addition the digital computer represents data internally using a

quite verbose but very robust form of representation called binary. Thus a

single transistor in a digital computer can only store two states, on and off.

Obviously to store a number to any sensible degree of precision, many

transistors are required.

Hybrid Computer

A computer that processes both analog and digital data.

A Hybrid Computer is a combination of computers that are capable of inputting

and outputting in both digital and analog signals. A hybrid computer system

setup offers a cost effective method of performing complex simulations.

Purpose: Special, General

Depending on the purpose we can categorize the computers mainly on to two.

Special Purpose Computers

Special Purpose Computers are used for special purposes like scientific

researches, atomic weapon researches, designing sophisticated vehicles,

weather forecasting etc.

Normally super computers come under special purpose computers as we

discussed earlier.

General Purpose Computers

General Purpose Computers are the normal computers we are using.

THE FIVE GENERATIONS OF COMPUTERSTHE FIVE GENERATIONS OF COMPUTERSTHE FIVE GENERATIONS OF COMPUTERSTHE FIVE GENERATIONS OF COMPUTERS

The history of computer development is often referred to in reference to

the different generations of computing devices. Each generation of computer is

characterized by a major technological development that fundamentally

changed the way computers operate, resulting in increasingly smaller, cheaper,

and more powerful and more efficient and reliable devices. Read about each

generation and the developments that led to the current devices that we use

today.

First Generation - 1940-1956: Vacuum Tubes

The first computers used vacuum tubes for circuitry and magnetic drums

for memory, and were often enormous, taking up entire rooms. They were very

expensive to operate and in addition to using a great deal of electricity,

generated a lot of heat, which was often the cause of malfunctions. First

generation computers relied on machine language to perform operations, and

they could only solve one problem at a time. Input was based on punched cards

and paper tape, and output was displayed on printouts.

The UNIVAC and ENIAC computers are examples of first-generation

computing devices. The UNIVAC was the first commercial computer delivered

to a business client, the U.S. Census Bureau in 1951.

Second Generation - 1956-1963: Transistors

Transistors replaced vacuum tubes and ushered in the second generation

of computers. The transistor was invented in 1947 but did not see widespread

use in computers until the late 50s. The transistor was far superior to the

vacuum tube, allowing computers to become smaller, faster, cheaper, more

energy-efficient and more reliable than their first-generation predecessors.

Though the transistor still generated a great deal of heat that subjected the

computer to damage, it was a vast improvement over the vacuum tube. Second-

generation computers still relied on punched cards for input and printouts for

output.

Second-generation computers moved from cryptic binary machine

language to symbolic, or assembly, languages, which allowed programmers to

specify instructions in words. High-level programming languages were also

being developed at this time, such as early versions of COBOL and

FORTRAN. These were also the first computers that stored their instructions in

their memory, which moved from a magnetic drum to magnetic core

technology. The first computers of this generation were developed for the

atomic energy industry.

Third Generation - 1964-1971: Integrated Circuits

The development of the integrated circuit was the hallmark of the third

generation of computers. Transistors were miniaturized and placed on silicon

chips, called semiconductors, which drastically increased the speed and

efficiency of computers.

Instead of punched cards and printouts, users interacted with third

generation computers through keyboards and monitors and interfaced with an

operating system, which allowed the device to run many different applications

at one time with a central program that monitored the memory. Computers for

the first time became accessible to a mass audience because they were smaller

and cheaper than their predecessors.

Fourth Generation - 1971-Present: Microprocessors

The microprocessor brought the fourth generation of computers, as

thousands of integrated circuits were built onto a single silicon chip. What in

the first generation filled an entire room could now fit in the palm of the hand.

The Intel 4004 chip, developed in 1971, located all the components of the

computer - from the central processing unit and memory to input/output

controls - on a single chip.

In 1981 IBM introduced its first computer for the home user, and in

1984 Apple introduced the Macintosh. Microprocessors also moved out of the

realm of desktop computers and into many areas of life as more and more

everyday products began to use microprocessors.

As these small computers became more powerful, they could be linked

together to form networks, which eventually led to the development of the

Internet. Fourth generation computers also saw the development of GUIs, the

mouse and handheld devices.

Fifth Generation - Present and Beyond: Artificial

Intelligence

Fifth generation computing devices, based on artificial intelligence, are

still in development, though there are some applications, such as voice

recognition, that are being used today. The use of parallel processing and

superconductors is helping to make artificial intelligence a reality. Quantum

computation and molecular and nanotechnology will radically change the face

of computers in years to come. The goal of fifth-generation computing is to

develop devices that respond to natural language input and are capable of

learning and self-organization.

COMPUTER GENERATIONSCOMPUTER GENERATIONSCOMPUTER GENERATIONSCOMPUTER GENERATIONS BRIEFLY BRIEFLY BRIEFLY BRIEFLY

EXPLANATIONEXPLANATIONEXPLANATIONEXPLANATION

First Generation [1946 – 1955]

We have just read about the first generation of computer. These

computers used value (vacuum tube) technology and had the main limitations

of very large electric power consumption and very little reliability.

In 1946, Eckert and Mouchley formed their company the UNIVAC

divitision of Remington Rand, Inc. This company made the first commercial

computer UNIVAC division in 1951. The UNIVAC had a memory capacity of

1000 words. It used magnetic tapes as input or output devices. It has used to

predict the election of Dwlight D.Eisen howen (one of the president of USA) in

1952.

A similar computer whirlwind one was built in 1951 by the

Massachusetts Institute of Technology, USA. It had a memory capacity of 2048

word.

In 1953 IBM installed its first computer the IBM 701 late in 1954 the

IBM developed a general purpose computer. IBM 650 computer was the most

popular one during that time. To over come the small storage capacity of IBM

650 and to produce a more efficient system the IBM developed IBM – 1401

add RAMAC 350.

The first generation computers were characterized by electronic tube

circuitry. Hence they were very large air – conditioned room. They had small

internal storage and were relatively showed. The First generation machines

used punched paper tape, punched card, magnetic wire, magnetic tape and

printers as input or output devices.

Second Generation [1957 – 1963]

With the advent of transition technology, a second generation of

computer comes into existence. These computers were smaller in size, more

reliable and highly efficient. These machines used English like language know

as High Level Language (HLL) for ease of operation and application in

business and scientific analysis many American and European companies

manufactured these machines. One of them the IBM – 1401 was the most

popular and some of the IBM – Organization use this model even today.

These computers were called the generations of computer. They have

faster access and were more reliable than the first generation of computer.

They were characterized by both vacuum tube (value) and discrete

transistor logic. By this time a wider range of input or output devices such as

higher performance magnetic tapes, magnetic drums and early

magnetic disks were available during the second generation

computer language such as FORTRAN and ALGOL were

introduced. The picture of a second generation

computer IBM – 7070 is shown below. The second generation of

computers started with the introduction of transistorized computer. The first of

these, the IBM 7090 was delivered in 11959 which were followed by the CDC

1604, The Phil co 2000 and Remington rondo’s UNIVAC, LARC.

Other widely used second generations of computer were

• IBM 1620

• IBM 1401

• IBM 7094

Third Generation [1964 – 1979]

In the sixtieth Integrated Circuits (IC) popularly know as ICs came in

the field of micro – electronics computers, that use a large junk of electronic

components were substantially benefited both from the point

of price reduction as well as size reduction these

machines consumed very little power and

were highly reliable.

These machines used more versa tike

programs like real time operation system,

multiprogramming, techniques and data base management, IBM – 370,

some of the most popular machine of this generation. Many others models are

given in table.

Manufacturer Model

Moore school of Electrical

Engineering

ENIVAC, EDVAC

Cambridge University EDSAC

Univas Univac I, Univac II

Burroughs E101, Burroughs 2022

Honey Well Data matic 1000

IBM Mark II, Mark III, 604 electronic

punch, calculating

IBM 650

IBM 702

IBM 704

IBM 705

IBM 709

National cash Register CRC, 1024, 102D

RC4 BIZMAC I, BIZMAC II

In the third generation computers more than were user could work with

the computer at the same time, where as first and second generation of

computers worked on a one – to – one basis.

Almost all computers introduced after 1966 were said to be third

generation computer. Most of the main frame computers use till the early

1980’s were third generation computers only a good.

Fourth Generation [1980 – Present]

Forth generation of computers were produced after 1980 the fourth

generation computer is used to designate micro computers which use large

scale integrated circuits (LSI) and very large scale integrated circuits (VLSI) in

the memory unit.

The invention of micro process or chip has created a revolution in the

reduction of price and size of this generation machines. These machines have

followed advantages over other generation.

1. These computers use advanced techniques to feed.

2. Data into them and to bring out processed data for use of the outside world.

Then can even be connected with the satellite communication links to trans

form information from one hart of the world at very high speed. These

Machines use advance application.

3. These machines use advance software such as process controverts,

computer aided design (CAD), electronic spread sheet (Lotus 123) and data

base management. Because of this these machines of table size type writer

have the same power which was available in very large computers of the

third generation.

Fifth Generation [Future]

We are presently straddling for the line between fourth and fifth

generation computers. In 1981 a group of Japanese design and build the fifth

generation machines this consortium believed generation machines. This

consortium believed it was possible for such a machine to per for the following.

� Accept Spoken instructions and such graphic images as photographs as

data input.

� Collect select and store useful data form newspapers, books tape

recorded speeches and other common sources.

� Translate foreign languages research and provide answers to questions

by using all available data.

� Learn from its own experiences program itself.

The US computer industry was at a dosed vantage in early phases of the

fifth generation race because antitrust laws restricted. The ability of companies

to co-operate by comparison the Japanese government brought together all of

its resources and all companies with in its electro nice industry for a coopered

fives concerted effort since these early days the government in the United

States has sanctioned special research and development cooperatives formed by

a number of computer companies induction some of the largest companies part

equally IBM hare established special developmental efforts budgets for

advanced computing capabilities. The fifth generation of computers is seen as

having increased processing capabilities, data handling and storage facilities

software will respond to the natural language of people.

The new technologies discussed below are seen as heys to implementing

fifth generation systems.

Optics and super conductive materials

� Parallel Processing

� Artificial Intelligence (AI)

� Language translation and non traditional input

� Special purpose machines

ARTIFICIAL INTELLIGENCEARTIFICIAL INTELLIGENCEARTIFICIAL INTELLIGENCEARTIFICIAL INTELLIGENCE

Computers are starting to simulate human thought and argument one

type of software application is known as Artificial Intelligence (AI). This

growing one of development scythe sizes computer science psychology

linguistics and other specialized fields to perform tasks with human live logic.

Among 5th AI developments expected in fifth generation computers are

heuristic problem solving techniques. The term heuristic describes are solved

through application of general rules and information based on experience.

Instead of following precise sequence of instructions to devices solutions

heuristic software applies rules proven to be effective in the past as example

heuristic techniques are used to develop programs that play chess vast human

of moves are possible in a same of chess with heuristic capabilities the

computer as able to evaluate different moves to bulls a games strategy thus.

The chess playing computer able to respond to variable situation is several

different ways computers scientists around the world are building system that

can learn form experience and are able to apply this in for motion to new

situations.

MAIN CIRCUIT BOARD OF A PCMAIN CIRCUIT BOARD OF A PCMAIN CIRCUIT BOARD OF A PCMAIN CIRCUIT BOARD OF A PC

A motherboard is the physical arrangement in a computer that contains

the computer's basic circuitry and components. On the typical motherboard, the

circuitry is imprinted or affixed to the surface of a firm planar surface and

usually manufactured in a single step. The most common motherboard design

in desktop computers today is the AT, based on the IBM AT motherboard. A

more recent motherboard specification, ATX, improves on the AT design. In

both the AT and ATX designs, the computer components included in the

motherboard are:

• The microprocessor

• (Optionally) coprocessors

• Memory

• Basic input/output system (BIOS)

• Expansion slot

• Interconnecting circuitry

Additional components can be added to a motherboard through its

expansion slot. The electronic interface between the motherboard and the

smaller boards or cards in the expansion slots is called the bus.

Bus

In a computer or on a network, a bus is a transmission path on which

signals are dropped off or picked up at every device attached to the line. Only

devices addressed by the signals pay attention to them; the others discard the

signals. According to Winn L. Rosch, the term derives from its similarity to

autobuses that stop at every town or block to drop off or take on riders

In general, the term is used in two somewhat different contexts:

(1) A bus is a network topology or circuit arrangement in which all

devices are attached to a line directly and all signals pass through each of the

devices. Each device has a unique identity and can recognize those signals

intended for it.

(2) In a computer, a bus is the data path on the computer's motherboard

that interconnects the microprocessor with attachments to the motherboard in

expansion slots (such as hard disk drives, CD-ROM drives, and graphics

adapters).

Chips

Chip" is short for microchip, the incredibly complex yet tiny modules

that store computer memory or provide logic circuitry for microprocessors.

Perhaps the best known chips are the Pentium microprocessors from Intel. The

PowerPC microprocessor, developed by Apple, Motorola, and IBM, is used in

Macintosh personal computers and some workstations. AMD and Cyrix also

make popular microprocessor chips.

There are quite a few manufacturers of memory chips. Many special-

purpose chips, known as application-specific integrated circuits, are being

made today for automobiles, home appliances, telephones, and other devices.

A chip is manufactured from a silicon (or, in some special cases, a

sapphire) wafer, which is first cut to size and then etched with circuits and

electronic devices. The electronic devices use complementary metal-oxide

semiconductor technology. The current stage of micro-integration is known as

Very Large-Scale Integration (VLSI). A chip is also sometimes called an IC or

integrated circuit.

Ports

On computer and telecommunication devices, a port (noun) is generally

a specific place for being physically connected to some other device, usually

with a socket and plug of some kind. Typically, a personal computer is

provided with one or more serial ports and usually one parallel port. The serial

port supports sequential, one bit-at a-time transmission to peripheral devices

such as scanners and the parallel port supports multiple-bit-at-a-time

transmission to devices such as printers.

Expansion Slots

In computers, a slot, or expansion slot, is an engineered technique for

adding capability to a computer in the form of connection pinholes (typically,

in the range of 16 to 64 closely-spaced holes) and a place to fit an expansion

card containing the circuitry that provides some specialized capability, such as

video acceleration, sound, or disk drive control.

Almost all desktop computers come with a set of expansion slots. These

help ensure that you'll be able to add new hardware capabilities in the future.

SIMM

A SIMM (single in-line memory module) is a module containing one or

several random access memory (RAM) chips on a small circuit board with Pins

that connect to the computer motherboard. Since the more RAM your computer

has, the less frequently it will need to access your secondary storage (for

example, hard disk or CD-ROM); PC owners sometimes expand RAM by

installing additional SIMMs. SIMMs typically come with a 32 data bit (36 bits

counting parity bits) path to the computer that requires a 72-pin connector.

SIMMs usually come in memory chip multiples of four megabytes.

The memory chips on a SIMM are typically dynamic RAM (DRAM)

chips. An improved form of RAM called Synchronous DRAM (SDRAM) can

also be used. Since SDRAM provides a 64 data bit path, it requires at least two

SIMMs or a dual in-line memory module (DIMM).

RIMM

In a computer, a RIMM is a memory module developed by Kingston

Technology Corp. that takes up less space inside the computer than the older

DIMM module and has different PIN characteristics. A RIMM has a 184-pin

connector and an SO-RIMM module has a 160-pin connector. An SO-RIMM is

smaller and is used in systems that require smaller form factors. While RIMM

is commonly believed to stand for "Rambus inline memory module," Kingston

Technology has trademarked "RIMM" and uses only that term.

A RIMM module consists of RDRAM chips that are attached using a

thin layer of solder, a metal alloy that, when melted, fuses metals to each other.

Solder balls on each chip create a metal pathway used to conduct electricity.

DIMM

A DIMM (dual in-line memory module) is a double SIMM (single in-

line memory module). Like a SIMM, it's a module containing one or several

random access memory (RAM) chips on a small circuit board with pins that

connect it to the computer motherboard. A SIMM typically has a 32 data bit

(36 bits counting parity bits) path to the computer that requires a 72-pin

connector. For synchronous dynamic RAM (SDRAM) chips, which have a 64

data bit connection to the computer, SIMMs must be installed in in-line pairs

(since each supports a 32 bit path). A single DIMM can be used instead. A

DIMM has a 168-pin connector and supports 64-bit data transfer. It is

considered likely that future computers will standardize on the DIMM.

VDU Interface

A device used for the real-time temporary display of computer output data.

Note: Monitors usually use cathode-ray-tube or liquid-crystal technology.

Synonyms video display terminal, video display unit, visual display unit.

VDU, or "video terminal", "video display terminal", VDT, "display terminal")

A device incorporating a cathode ray tube (CRT) display, a keyboard and a

serial port. A VDU usually also includes its own display electronics which

store the received data and convert it into electrical waveforms to drive the

CRT.

VDUs fall into two categories: dumb terminals and intelligent terminals

(sometimes called "programmable terminals").

Early VDUs could only display characters in a single preset font, and these

were confined to being layed out in a rectangular grid, reproducing the

functionality of the paper-based teletypes they were designed to replace.

Later models added graphics facilities but were still driven via serial

communications, typically with several VDUs attached to a single multi-user

computer. This contrasts with the much faster single bitmap displays integrated

into most modern single-user personal computers and workstations.

The term "Display Screen Equipment" (DSE) is used almost exclusively in

connection with the health and safety issues concerning VDUs.

HISTORY OF THE MOTHERBOARDHISTORY OF THE MOTHERBOARDHISTORY OF THE MOTHERBOARDHISTORY OF THE MOTHERBOARD

Before starting to look at the motherboard inn detail it is worthwhile

examining the g\history of its development over the years. Motherboards have

changed radically in order to accommodate the latest developments in

technology such as new CPUs, different types of memory, different expansion

buses (and cards), and to some extend to meet the need for smaller system

units.

Looking back, the earliest computers were often produced as kits aims at

hobbyist and electronic enthusiast. With these kits the electrical components

were installed using a commercial board approach with the manually soldered

components. The customer essentially built the computer according to a set of

assembly instructions and standard components.

As computer design and manufacturing technique developed, computers

began to incorporate a separate simple circuit board with a logical layout for

placing the electrical components. This was basically the first motherboard and

led to the development of chip sockets and components pinholes wit an etched

circuit. This enables a production assembly line of workers to manually insert

and solder all discrete parts in place.

With the development of new manufacturing techniques such as wave

soldering and machines for large-scale automation of components installation

quantity and production rates improved. With the rapid development of

manufacturing technique to increase the no\umber of transistors per chip

offered by Large Scale Integration (LSI) and then Very Large Scale Integration

(VLSI), motherboard design has evolved to the point where the number of

physical components required for a system has been reduced dramatically.

When IBM introduced the first popular PC 5150 in 1981, the

motherboard contained a large number of memory chips conventionally taking

up a larger part of the motherboard surface area. Other semiconductors devices

were installed in a simple row format alone with an extends system bus

offering five 8 bit ISA standard expansion card slots.

The physical size of this early motherboard was largely a reflection of

the number of chips supported and design of bus and peripheral ports. The

original motherboard used in the PC 5150 had over 100 Integrated Circuit (IC)

chips and naturally the introduced of LSI and VSLI led to a reduction of the

number of support chips required. This physical size and the layout of major

components are termed as a board from factor and as we shall see later, are

used in identifying difficulty types of motherboard.

The first real standard motherboard was introduced with the IBM PC XT

in 1983. The number of expansion slots was increased from five to eight, with

less space allotted between the slots. This motherboard set a standard for board

design and was taken up by many other PC manufactures in the transition to 16

bit processing; the form factory this board become known as the Baby-AT.

In 1984, IBM brought out a new 16-bit processor PC called the IBM PC

AT. This used a large physical size from factor boars then the Baby At and was

called Full Size AT.

This broad has eight bit slots, with six of those having a slot extension to

support 16 bit PC cards.

Many IBM compatible suppliers incorporating the 16 bit features of the

Full Size AT board manufactured the Baby-AT board. These boards were so

similar that the Baby- AT could easily replace the Full Size AT board as an

upgrade. Both boards initially had a single 5 pin DIN keyboard connectors

mounted on the motherboard with a hole in the computer chassis rear panel to

provide access. The 5-pin DIN keyboard socket on this motherboard was

eventually replaced with a mini-DIN 6-pin PS/2 type keyboard socket before

this motherboard design was eventually superseded.

During 1987 Western Digital created new motherboard from faction

called the LPX and mini-LPX. These boards were fro incorporation slim-line or

low profile computers.

A major difference with this motherboard is that PC expansion cards

cannot be installed vertically because of the limited computer casing height.

Instead these boards have a single system bus slot on the motherboard from

which a special extender card or riser card is mounted at right angles. The riser

card has built-in expansion slot and supports PC expression card mounted

horizontally.

LPX or Mini-LPX from factor motherboards can easily be recognized,

external to a computer by the use of horizontal chassis opening for expanses

slots on desktop or vertical slots when the motherboard is mounted in a tower

computer case. An LPX board has two PS/2 type connectors (one fro the

keyboard and one for a mouse) mounted on the motherboard with two 9 pin

serial sockets and single parallel sockets.

Another from factor motherboard, called the NLX is very similar to the

board to be used in PCs until the mid to late 1990s. By then a new motherboard

from factor called ATX began to replace the Baby-AT.

In 1997 Intel introduced a new motherboard from factor called ATX.

Combining build and components qualities from both the Baby-AT and LPX

boards with new boards design features; this motherboard is the basis for the

current most popular standard.

It is also has the new 20 pin power supply connectors with supplied

+3.3.V for processor supply.

Because of the advances in VLSI motherboard manufactures have been

able to save a considerable amount of space in their designs. This extra many

of the functions, such as video audio and new networking that previously

required additional expansion card.

Just as with the original AT deign many manufacturers have introduced

a compact version of the ATX format motherboard called the Mini ATX. With

the integration of more and more functions onto the motherboard the need for

expansion slots has deceased. Therefore instead of providing seven expansion

slot as with the ATX from factor the Mini ATX motherboard typically has just

three or four factories the Mini means that the Mini ATX motherboard can be

filtered in to cheaper more compact system unit cases. The major drawback of

the Mini ATX from memory slot and only allow one or two Dual In-Line

Memory Modules (DIMMs) to be installed.

Identifying the from factors of a motherboard can be quite difficult,

although most manufactures will label product to aid identification. Naturally

any motherboard document should clearly state the from factor.

PROGRAMMING LANGUAGESPROGRAMMING LANGUAGESPROGRAMMING LANGUAGESPROGRAMMING LANGUAGES

Hundreds of programming languages exist. Only a few, however, are

used widely enough today for the industry to recognize them as standards.

Most of these are high-level languages that work on a variety of computers.

This section discusses these programming languages, their origins, and their

primary purpose. Although the

Java programming language is used in many business applications

today; it originally was used primarily for Web development. Thus, Java is

discussed in the Web page development section of this chapter.

To illustrate the similarities and differences among programming

languages, figures on the following pages show program code in several

programming languages. The code solves a simple payroll problem —

computing the gross pay for an employee.

The steps to compute gross pay can vary from one system to another.

The examples on the following pages use a simple algorithm to help you easily

compare one programming language with another.

To compute the gross pay, first multiply the regular time hours worked

by the hourly rate of pay to obtain the regular time pay. If the employee has

overtime hours, the employee’s overtime pay is 1.5 times the hourly rate of pay

multiplied by overtime hours. Then, add the regular time pay and overtime pay

together.

BASIC

John Kemeny and Thomas Kurtz developed a programming language

called Beginner’s All-purpose Symbolic Instruction Code, or BASIC, in the

mid-1960s at Dartmouth College. Kemeny and Kurtz designed BASIC for use

as a simple, interactive problem-solving language. BASIC originally was

intended as the language used in a student’s first programming course because

it is so easy to learn and use.

Today, BASIC is used on both personal computers and mid-range

servers to develop some business applications. Many versions of BASIC exist,

including QBasic, QuickBasic, and MS-BASIC.

Visual Basic

Developed by Microsoft Corporation in the early 1990s, Visual Basic is

a Windows based

Application that assists programmers in developing other event-driven

Windows-based applications. The first step in building a Visual Basic

application is to design the graphical user interface using Visual Basic objects.

Visual Basic objects, or controls, include items such as command buttons, text

boxes, and labels.

Next, you write any code needed to define program events. An event in

Visual Basic might be the result of an action initiated by a user. When a user

clicks an object in a Visual Basic application, the application executes the

Click event. You define Visual Basic events using code statements written in

Visual Basic’s built-in programming language.

COBOL

COBOL (Common Business-Oriented Language) developed out of a

joint effort between the United States government, businesses, and major

universities in the early 1960s. Naval officer Grace Hopper, a pioneer in

computer programming, was a prime developer of the COBOL language.

COBOL is a procedural programming language designed for business

applications. Although COBOL pro grams often are lengthy, their English- like

statements make the code easy to read, write, and maintain (Figure 15-26).

COBOL is especially useful for processing transactions on main frames.

COBOL programs also run on other types of computers. The most popular

personal computer COBOL program is Micro Focus Net Express®, which

allows you to create procedural and object oriented

COBOL programs and migrate them to the Web.

C

The C programming language, developed in the early 1970s by Dennis

Ritchie at Bell Laboratories, originally was designed for writing system

software. Today, a variety of software programs are written in C. This includes

operating systems and application software such as word processing and

spreadsheet programs.

C is a powerful language that requires professional programming skills.

Many programmers use C for business and scientific problems. C runs on

almost any type of computer with any operating system, but it most often is

used with the UNIX operating system. In fact, most of the UNIX operating

system is written in C.

C++

Developed in the 1980s by Bjame Sroustrup at Bell Laboratories, C++

(pronounced SEE-plus-plus) is an object-oriented programming language. C++

is an extension of the C programming language. It includes all the elements of

the C language plus has additional features for working with objects, classes,

events, and other object oriented concepts. Programmers commonly use C++ to

develop application software, such as word processing and spreadsheet

programs, as well as database and Web applications. Although C++ is an

outgrowth of the C programming language, you do not need C programming

experience to be a successful C++ programmer.

Some programmers use a newer programming language called C#

(pronounced SEE-sharp). C# com bines features of C and C++ and is best

suited for development of Web applications.

JAVA

Developed by Sun Microsystems, Java is a compiled object-oriented

programming language used to write stand-alone applications, as well as

applets and servlets.

Java applet examples might include input forms, rotating images,

fireworks, interactive animations, or a game. Figure 15-37 shows a sample Java

program and its resulting screen.

The Java language is very similar to C++. One difference is that Java

source code is compiled into byte code, instead of object code. The operating

system cannot execute byte code. A Java interpreter executes the byte code.

Java-enabled Web browsers contain Java byte code interpreters.

Code segments used to create a Java application are called JavaBeans, or

Beans. A JavaBeans is platform independent. This enables the code to run on

any computer or operating system. Many programmers believe that Java will be

the programming language of the future because of its simplicity, robustness,

and portability.

INTEL PROCESSORS: NOW AND THENINTEL PROCESSORS: NOW AND THENINTEL PROCESSORS: NOW AND THENINTEL PROCESSORS: NOW AND THEN

There might come a time when you will have to replace or

upgrade a processor in order to fix a problem. Listed

below are details and characteristics of some of

the most popular chips from Intel and other

manufacturers.

8088

This is the chip found in most of the IBM XT-class machines. The 8088

came in a 40- pin DIP package. Translated, this means the 8088 is a small,

rectangular chip with two rows of 20 pins each. The original speed of this chip

was 5MHz. Later versions reached a top speed of about 8MHz.

80286

Introduced in 1981 by Intel, this chip became the mainstay of the AT-

class computers. The chip itself was packaged in a square called a Pin Grid

Array (PGA) instead of a rectangle.

The chip contained about 130,000 transistors -- about 100,000 more than

the 8088.

80386

The 80386 was introduced to the market in 1985 and came in two

different types: DX and SX. This chip was also packaged in the PGA

configuration. The 80386 contained

250,000 transistors and also provided features like multitasking of DOS

programs and a 32-bit data path. The 32-bit data path was available only in the

DX version, while the SX version had a 16-bit data path. This made the SX

more compatible with the 80286 computers and hardware.

80486

The 80486 chip was actually a “beefed-up” version of the 80386. The

486 processor was a composite of three other chips. The 80486 consisted of a

386 chip, a 385 cache controller and a 387 math co-processor. The 486

contained about 1.25 million transistors and 8k of internal cache memory. It

provided a 32- bit data path and a built-in math co-processor. Like the 80386,

the 80486 came in two types: the DX and SX. The 80486 SX had all the

features of the DX version minus the math co processor. Actually, the math co-

processor was still on-board but disabled in the SX version.

80486DX2

To understand the 80486DX2, it is important to understand another Intel

creation designed to increase system speed: the “Overdrive” chip. The

Overdrive chip could run at two clock speeds simultaneously. If the chip was

placed on a 486SX1 25MHz system board, it was placed in the socket for the

co processor chip and took over for the 486SX chip. When data was passed

through the Bus or memory, it was done at the speed of the processor; in this

case 25MHz. This is referred to as the external clock speed. All the internal

calculations were done at twice the 25MHz speed, at 50MHz. The 80486DX2

is very similar to the Overdrive chip in that it runs at a certain external speed

“X MHz” but performs all internal calculations at “two times X.”

80486DX4

The plot thickens. DX4 chips used a technology developed by IBM

called Clock Tripler (nicknamed “Blue Lightning”). Under an agreement with

Intel, IBM manufactured 486 chips using the Intel mask. Using their own

Clock Tripler technology, IBM took an Intel 486DX 25MHz chip and

increased its speed to approximately 75MHz.

Intel followed suit and announced the 80486DX/99MHz chip. This chip

would run external speeds of 331VIHz and perform internal calculations at

99MHz.

Pentium

In 1993 Intel introduced the Pentium processor. The initial market

response was not overwhelming, but the Pentium has now become the standard

for personal computers sold today. The Pentium processor contains over 3

million transistors and provides a 64- bit data path.

The first generation of Pentium chips was subject to heat problems.

Computers not designed to deal with high temperatures tended to experience

high failure rates.

Newer versions of the Pentium chip were designed to run cooler. System

boards and internal components were also designed to cope with the higher

temperatures.

The Pentium chips will run both internal calculations and external

processing at the same speed. Another unique feature of the Pentium chip is the

cache. The Pentium has two 8KB caches: one that is used for program code and

another used for data cache. The Pentium chip was also designed to be fault

tolerant, something Intel refers to as “superscalar.” This feature is only

functional when the Pentium chip is installed on a system board that will

support multiple processors. Fault tolerance simply means that when two

processors are present on the system board, the second chip takes over if the

first chip fails.

Pentium Pro

The Pentium Pro processor has a different look and design than the other

chips. It is the first Intel processor to combine Level1 (L1) and Level 2 (L2)

cache in the same package as the CPU. The Pentium Pro processor is a dual-

chip configuration that houses the Pentium Pro CPU on one side of the dual-

cavity package and the L2 cache memory on the other. According to Intel, this

simplifies system design and saves space. The Pentium Pro processor has about

21 million transistors in total. The CPU core has 5.5 million transistors and the

L2 cache has 15.5 million. The Pentium Pro was designed to support multiple

Pentium Pro processors connected in parallel. The Pentium Pro is a true 32-bit

processor. It operates at speeds of 200MHz.

MMX Technology

The MMX technology is based on a new set of instructions that are built

into Intel’s Pentium microprocessors. This new instruction set enables the chip

to efficiently process video and audio data. Prior to the MMX technology,

multimedia operations, in video and sound, had to be handled by separate

components like sound cards and enhanced video boards. These same functions

can now be managed by the processor.

MMX chips’ internal memory (cache memory) has doubled in size

(32KB). This is the area in memory that holds recently accessed data. It is

designed to speed up subsequent requests to this data. This means that more

instructions and data can be stored internally in the chip, reducing the number

of times the processor has to access slower external memory. Most multimedia

applications run dramatically faster and smoother. To really get the most out of

the new MMX chip, you must run the enhanced MMX applications that have

been written to exploit the true power of the technology.

Pentium II

The Pentium II processor is available in speeds from 233MHz to

450MHz. It utilizes the innovative 0.25 micron manufacturing process that

enables these CPUs to include over 7.5 million transistors. This results in more

power in less space. The processor core is packaged in the Single Edge Contact

(SEC) cartridge enabling ease of design and flexible motherboard architecture.

The processor also includes MMX technology. The Dual Independent Bus

(DIB) architecture increases bandwidth and performance over single-bus

processors.

Pentium III

The new Intel Pentium III processor is groundbreaking in terms of

graphics capabilities. The chip has been built to exploit many of the new and

expanding 3-D graphic images and their manipulation. The following are some

of the highlights of the Pentium III.

Added 70 new instruction sets for enhanced graphics, video and sound.

The Pentium III processor introduced a new processor instruction set called

Streaming SIMD Extensions (SSE). Single-instruction, Multiple Data (SIMD)

was the instruction set used by the MMX processor to improve multimedia

performance. The Pentium III SSE instruction set was designed to further

enhance multimedia performance.

An embedded serial number to help companies with an inventory of

computers. This feature will also enhance on line security transactions.

Although it also raises some very serious privacy concerns.

Clock speeds in excess of 800 MHz.

Pentium IV

Pentium 4 (P4) is the Intel processor (codenamed Willamette) that was

released in

November 2000. The P4 processor has a viable clock speed that now

exceeds 2 Gigahertz (GHz) - as compared to the 1 GHz of the Pentium 3.

P4 had the first totally new chip architecture since the 1995 Pentium

Pro. The major difference involved structural changes that affected the way

processing takes place within the chip, something Intel calls Net Burst micro

architecture. Aspects of the changes include: a 20-stage pipeline, which boosts

performance by increasing processor frequency; a rapid-execution engine,

which doubles the core frequency and reduces latency by enabling each

instruction to be executed in a half (rather than a whole) clock cycle; a 400

MHz system bus, which enables transfer rates of 3.2 gigabytes per second

(GBps); an execution trace cache, which optimizes cache memory efficiency

and reduces latency by storing decoded sequences of micro operations; and

improved floating point and multimedia unit and advanced dynamic execution,

all of which enable faster processing for especially demanding applications,

such as digital video, voice recognition, and online gaming.

P4's main competition for processor market share is the AMD Athlon

processor.

Celeron

The Celeron is Intel’s entry into the low-end microprocessor market. It

is based on the same architecture as the Pentium II. However, it lacks some of

the performance features of the Pentium II family. The newest of the Celeron

CPUs include an L1 and L2 on-board cache. This configuration means that the

cache is actually accessed at the same clock speed as the processor operates.

When comparing the Celeron’s L2 cache to the Pentium II’s cache you will

find it somewhat smaller (i28 KB) as compared to the Pentium II’s (512 KB)

cache. However, since the Celeron’s cache is built in and the Pentium’s is not,

their effective L2 speeds are roughly the same. The Celeron processor supports

clock speeds up to 466 MHz and can be mounted in a Slot 1 motherboard. Intel

is marketing this chip for the entry level PC, capable of providing performance

solutions geared to the home and light business use.

Itanium Processor

The Itanium processor, formerly known as the Merced IA- 64, is unique

with its Slot M configuration and L3 cache. The L3 cache is small in physical

size and is not located on-board the chip itself but is bundled instead within the

processor package.

Currently there are two flavors: the 800 MHz and 1000MHz versions.

Motorola Chip Family

The Motorola chip set is not quite as well known in the PC market as

Intel. For the most part, it is associated with the Apple computer line.

68000

Introduced in 1979, the 68000 chip is closely associated with the Apple

computer.

The 68000 chip employed a 32- bit design and used a 16-bit data Bus.

The 68000 was far ahead of Intel’s efforts at the time.

68010

In 1982, Motorola introduced the 68010 chip. The major difference

between the68000 and the 68010 was the addition of virtual memory support.

This chip also incorporated internal cache which made the processing of sub-

routines much faster.

This chip did not find widespread use in the computer world but was

used extensively in Motorola’s component division.

68020

This chip was introduced in 1984 as the first full 32-bit chip in the

Motorola line. The 68020 had the ability to access 4 GB of RAM and utilized

floating point processing capabilities. It was used in the Macintosh II and found

widespread use in minicomputers as well.

68030

Introduced to the market in 1987, the 68030 had all the features of the

68020 plus demand page memory management. Other enhancements to the

chip also increased the speed of the chip. It was used most widely used in the

Macintosh II series of computers.

68040

In 1989, Motorola’s answer to Intel’s 486 was the 68040.

However, the 68040 did not gain the market share that Intel’s486

enjoyed.

Power PC

Apple, IBM and Motorola all joined together to develop the PowerPC

family of chips.

PowerPC stands for Performa2 Optimization with Enhanced RISC.

Currently Apple incorporates the chip in its PowerMac series of computers.

This chip can also be used in everything from laptops to computers functioning

as servers.

Other Chips

Cyrix

Cyrix (SYE-rihks) is a family of low-end, low-cost microprocessors

intended for personal computers and personal information devices. Cyrix

competes with Intel in the low-cost, low-end market for PC microprocessors.

Typically, Cyrix has been able to under-price Intel for comparable low-end

microprocessors.

Cyrix began making semiconductors in 1988. Its first product was a

math coprocessor. About 1992, it introduced its first microprocessors that

would handle the instruction set specified by Intel’s 486 microprocessors.

AMD K6

The AMD K6 is AMD’s answer to the Intel Pentium series of

microprocessors.

Although it is considerably less expensive than the Pentium II

processors, according to many industry based benchmarks the K6 has slightly

better performance. The KG has 64K of Li and L2 cache. The K6 processor can

be mounted in a Socket 7 based motherboard.

AMD offers multiple K6 versions which support a 66 MHz bus and

operate at clock speeds starting at 166 MHz. There is also a 266 version,

referred to as the K6+. The K6+ (266) operate at about 2.5 volts of power at a

very low heat output making it an ideal candidate for the laptop computing

market.

K7 (Athlon)

The K7 processor was the first AMD product to support a 200 MHz bus

and to reach a 1 Gigahertz (one billion) clock speed. The K7 classification was

actually the development name for the Athlon processor. Compaq and Gateway

are among companies that manufacture computers that include the 1 GHz

Athlon. As the successor to AMD’s K6 microprocessor the K7 compares

favorably to Intel’s Pentium III. The K7 has a 128 KB Li and L2 cache that is

built into the chip itself, significantly increasing performance.

THE COMPONENTS OF A COMPUTERTHE COMPONENTS OF A COMPUTERTHE COMPONENTS OF A COMPUTERTHE COMPONENTS OF A COMPUTER

A computer consists of a variety of hardware components that work

together with software to perform calculations, organize data, and

communicate with other computers.

These hardware components include input devices, output devices, a

system unit, storage devices, and communications devices.

Input Devices

An input device is any hardware component that allows a user to enter

data and instructions into a computer. Six commonly used input devices are the

keyboard, mouse, microphone, scanner, digital camera, and PC camera.

A computer keyboard contains keys that allow you to type letters of the

alphabet, numbers, spaces, punctuation marks, and other symbols. A computer

keyboard also contains other keys that allow you to enter data and instructions

into the computer.

A mouse is a small handheld device that contains at least one button.

The mouse controls the movement of a symbol on the screen called a pointer.

For example, as you move the mouse across a flat surface, the pointer on the

screen also moves.

With the mouse, you can make choices, initiate a process, and select

objects.

A microphone allows a user to speak to the computer to enter data and

instructions into the computer. A scanner reads printed text and pictures and

then translates the results into a form the computer can use. For example, you

can scan a picture, and then include the picture when creating a brochure.

With a digital camera, you can take pictures and transfer the photo

graphed image to the computer, instead of storing the images on traditional

film. A PC camera is a digital video camera attached to a computer. A PC

camera allows home users to create a movie and take digital still photographs

on their computer. With a PC camera, you also can have a video telephone call

— where someone can see you while communicating with you.

Output Devices

An output device is any hardware component that can convey

information to a user. Three commonly used output devices are a printer, a

monitor, and speakers.

A printer produces text and graphics on a physical medium such as

paper or transparency film. A monitor, which looks like a television screen,

displays text, graphics, and video information. Speakers allow you to hear

music, voice, and other sounds generated by the computer.

System Unit

The system unit, sometimes called a chassis, is a box-like case made

from metal or plastic that protects the internal electronic components of the

computer from damage. The circuitry in the system unit usually is part of or is

connected to a circuit board called the motherboard.

Two main components on the motherboard are the central processing

unit and memory. The central processing unit (CPU), also called a processor, is

the electronic device that interprets and carries out the basic instructions that

operate the computer.

During processing, the processor places instructions to be executed and

data needed by those instructions into memory. Memory is a temporary holding

place for data and instructions.

Both the processor and memory consist of chips. A chip is an electronic

device that contains many microscopic pathways that carry electrical current.

Chips, which usually are no bigger than one-half inch square, are packaged so

they can be attached to a motherboard or other circuit board.

Some computer components, such as the processor, memory, and most

storage devices, are internal and reside inside the system unit. Other

components, such as the key board, mouse, microphone, monitor, printer,

scanner, digital camera, and PC camera, usually are located outside the system

unit. These devices are considered external. A peripheral is any external device

that attaches to the system unit.

Storage Devices

Storage holds data, instructions, and information for future use. Storage

differs from memory, in that it can hold these items permanently. Memory, by

contrast, holds items only temporarily while the processor interprets and

executes instructions.

A storage medium (media is the plural) is the physical material on which

a computer keeps data, instructions, and information. A storage device records

and retrieves items to and from a storage medium. Storage devices often

function as a source of input because they transfer items from storage into

memory.

Common storage devices are a floppy disk drive, a Zip® drive, a hard

disk drive, a CD-ROM drive, a CD-RW drive, a DVD-ROM drive, and a

DVD+RW drive. A drive is a device that reads from and may write on a

storage medium. This media includes floppy disks, Zip® disks, hard disks, and

compact discs.

A floppy disk consists of a thin, circular, flexible disk enclosed in rigid

plastic. A floppy disk stores data, instructions, and information using magnetic

patterns. You insert and remove a floppy disk into and from a floppy disk

drive. A Zip® disk is a higher capacity disk that can store the equivalent of up

to 170 standard floppy disks.

A hard disk provides much greater storage capacity than a floppy disk.

A hard disk usually consists of several circular platters that store items

electronically. These disks are enclosed in an airtight, sealed case, which often

is housed inside the system unit.

Some hard disks are removable, which enables you to insert and remove

the hard disk from a hard disk drive, much like a floppy disk. Removable disks

are enclosed in plastic or metal cartridges so you can remove them from the

drive. The advantage of removable media such as a floppy disk and removable

hard disk is you can take the media out of the computer and transport or secure

it.

A compact disc is a flat, round, portable medium that stores data using

microscopic pits, which are created by a laser light. One type of compact disc is

a CD-ROM, which you can access using a CD-ROM drive. A Picture CD is a

special type of CDROM that stores digital versions of photographs for

consumers.

A variation of the standard CD-ROM is the rewriteable CD, or CD-RW.

In addition to accessing data, you also can erase and store data on a CD-RW.

To use a CD-RW, you need a CD-RW drive. Another type of compact disc is a

DVD-ROM, which has tremendous storage capacities — enough for a full-

length movie. To use a DVDROM, you need a DVD drive. A variation of the

standard DYD-ROM is the rewriteable DYD, or DVD+RW.

PC Cards and memory cards are popular types of miniature storage

media. You then can transfer the items, such as the digital photographs, from

the media to your computer using a device called a card reader.

Communications Devices

Communications devices enable computer users to communicate and to

exchange items such as data, instructions, and information with another

computer.

A modem is a communications device that enables computers to

communicate usually via telephone lines or cable. Modems are available as

both external and internal devices.

Communications devices, such as modems, allow you to establish a

connection between two computers and transmit items over transmission

media, such as cables, telephone lines, or satellites.

INPUT DEVICESINPUT DEVICESINPUT DEVICESINPUT DEVICES

Keyboard devices

Offline Data Preparation Methods

Table 1 below illustrates the Data Preparation Devices with

corresponding input devices and media. These methods need special data

preparation devices. The term “Off linen is used because this activity is done

outside the computer and before input. In Sri Lanka the punch card system was

popular with the computers used from 1969 to the late 1970s. Later, it was

replaced by Key-to-Diskette systems, which are still in use in Sri Lanka at a

few places having high volume batch processing and less time critical

applications such as: Data Processing of Public Examinations, Provident Fund

applications, Census applications, Archival of high volume business documents

etc.

Input Media Input Devices Data Preparation

Devices

Punch Card Card Reader Key Punch & Verifier

Machines

Magnetic Tape Magnetic Tape Drive Key-To-Tape Encoder

or Key-To-Disk System

Magnetic diskette Diskette Reader / Drive Key-To-Diskette System

Table I – The Data Preparation Systems

Key Board Devices - On-line Terminals

The more common types of terminals are:

Visual Display Unit (VDU) or Video Terminal

VDU has ‘a television’ type screen and a keyboard. Here, input is by a

keyboard and output through display on Cathode Ray Tube (CRT). This is the

most common method of input.

General Features of a Video Terminal

01. It is an input/output (dual purpose) device.

02. The keyboard generally resembles a typewriter (QWERTY) keyboard,

but there is a wide range of variations.

03. Display clarity (Resolution) depends on the pixel density. Pixel is the

smallest display element to represent single color. Each character is formed

by combination of pixels.

04. Standard screen display includes 24 rows by 80 column character matrix

totaling 1920 characters.

05. Screen movement is generally; Line by line - Scrolling or page by page -

Paging.

06. Most of Video Terminals are ‘dumb’ terminals. New models appear now

in the market includes microprocessor with various levels of facilities.

Terminals

A terminal is a form of input (and output) device that connects you to a

mainframe or other type of computer called a host computer or server. There

are four types of terminals:

A dumb terminal can be used to input and receive data, but it cannot

process data independently. It is used only to gain access to information from a

computer. Such a terminal may be used by an airline reservations clerk to

access a mainframe computer for flight information

An intelligent terminal includes a processing unit, memory, and

secondary storage such as a magnetic disk. Essentially, an intelligent terminal

is a micro computer with communications software and a telephone hookup

(modem) or other communications link. These connect the terminal to the

larger computer or to the Internet. Microcomputers operating as intelligent

terminals are widely used in organizations.

A network terminal is also known as a thin client or network computer,

is a low-cost alternative to an intelligent terminal. Most network terminals do

not have a hard-disk drive and must rely on the host computer or server for

application and system software. These devices are becoming increasingly

popular in many organizations.

An Internet terminal, also known as a Web terminal, provides access to

the Internet and displays Web pages on a standard television set, these special

purpose terminals have just recently been introduced to offer Internet access to

people without microcomputers. Unlike the other types of terminals, Internet

terminals are used almost exclusively in the home.

A Point-of-Sale (POS) Terminal

A Point-of-Sale (POS) Terminal is a smart terminal used very much like

a cash register, but it also captures sales and inventory’s data at the point of

sale and sends it to the central computer for processing. Many supermarkets

have POS terminals that are connected directly to a central computer so that the

sales data can be immediately recorded. This type of

terminal usually displays the price, the product number,

and possibly the product description. In

addition, this type of terminal is equipped with

a cash-register-type keyboard, a cash drawer, and

a printer to print the receipt. It can operate on standalone basis and data stored

can be transferred to the main computer by using a computer medium such as a

diskette.

Banking / Financial Transaction Terminal

The most common terminals are:

01. Automatic Teller Machine (ATM)

A special intelligent terminal located outside the bank for a customer to

operate on his own to perform a limited number of banking transactions.

e.g.: cash withdrawal, cash transfers, utility bill payment etc.

02. Teller Operator terminal

This is a specialized dumb/smart terminal for the bank teller operators who

work in the front office of a bank to handle customer transactions.

03. Normal Video Terminals

Portable Terminal

It is consists of a Key Board, flat screen monitor and built in

communication software/hardware which can connect from a

remote location through a communication link to a

computer. The portability of the terminal is due to its

light weight. There are a wide range of products available.

(e.g.: Terminal for traveling salesman.)

Non Keyboard Devices

Mouse

The mouse is one of the devices connected to the computer by a small

cable. As the mouse is rolled across the desktop, the cursor moves across the

screen. When the cursor reaches the desired location, the user usually pushes

button on the mouse once or twice to signal a menu selection

or a command to the computer. Mouse technology is

often used with graphics- oriented personal computers. With

special software for graphics, the mouse can be used

like a pen or a Paint Brush to create figures and patterns

directly on the video display screen. e.g.: use with Corel Draw or Howard

Graphics, Desk Top Publishing Applications etc.

Joystick

It is a device which contains lever which can be used to

move objects on the screen.

e.g.: It is normally used to play computer games.

Light Pen

The light pen is a special attachment to a graphics terminal. The pen is

touched on the video display screen at the desired location and

switched on, and then you can draw the image on the screen.

Light pens are frequently used by graphic designers, illustrators,

and drafting engineers. Of course, data may also be entered using

keyboard e.g. Computer Aided Design (CAD), Architectural applications etc.

Touch Screen

Limited amounts of data can be entered via a terminal or a

microcomputer that has a touch screen. The user simply

touches the screen at the desired locations, marked by

labeled boxes, to point out” choices to the computer. e.g.:

Inquiry Terminals for general public such as

Terminals located in the lobby areas of a large building complex. This will

enable users to operate without much technical knowledge & skill.

Scanning Devices

Scanners

A Digital Scanner translates images such as pictures or documents into

digital form. This is one area where substantial research &

development has been taking place in the recent past.

A wide variety of products are now available in the

marketplace. The most common products are:

Hand Held Scanner

Used mostly with small scale publishing (Desk Top

Publishing) systems to input pictures, logos etc.

Flat Bed Scanner

Used to input text based documents with or

without images. Special software packages are now

available to process these text based images such as

editing, merging etc.

Character Scanners

These are hand held devices which can read data printed in special type

fonts (e.g.: OCR) or hand written data based on recommended guidelines. In

addition, there are Optical Character Readers which operate at high speed to

handle high volume batch oriented input like Electricity billing meter readings.

Optical Character Recognition (OCR)

Optical character recognition is a device that is used to scan the text,

which is found on a document, and then the data is converted into electrical

signals for the computer. This device can be used to read a special type of font.

However, the more expensive OCR devices can read a variety of fonts; some

can even read hand written documents.

Optical Mark Recognition (OMR)

The input device is Optical Mark Reader. In some of the foreign

examinations like SAT or TOEFL the candidate application forms as well as

the answer sheets are specially designed (Mark Sense Cards) to record data by

using pencil marks. Open University of Sri Lanka and University of Colombo

BIT program also use a similar method. Data recorded in this form is converted

into computer-usable form by an Optical Mark Reader (OMR). The OMR

device has a high-intensity light inside which is directed in the form of a beam

at the sheet of paper being fed through it. The beam scans the marked forms

and detects the number and location of the pencil marks. The data is then

converted into electrical signals for the computer. OMRs come in a variety of

sizes and shapes that depend on the size of the forms to be read and the

required loading and processing capacity of the reader.

Magnetic-Ink Character Recognition (MICR)

This is specially designed for the input of high volume cheques in the

banking industry. The advantages of the MICR system are that Human

involvement is minimum, thus the potential for errors is small, The codes can

be read by both people and machines, It is fast, automatic, and reliable (2400

checks/mm). The cheque leaf taken into the machine, and magnetize the ferric

particles present in the data printed at the bottom edge of it. At the first read

station it recognizes data based on magnetic induction & converts into

electrical signals. Generally at the second read station it reads again & compare

with the first reading for accuracy. In addition to reading, it sort the cheque

leaves in a bundle according to the bank code & output to respective pigeon

holes. e.g.; Cheque Clearing House of Sri Lanka.

Bar Code Reader

Bar Code is a collection of thick and thin lines and spaces that represent

data in binary.

E.g.:

• Parcel tracking system in courier companies

• File tracking system in an office

• Issue of items in a supermarket.

• Record the movement of books in a library

In courier application the parcel reference number is bar coded &

recorded in all relevant documents & the parcel it. This reference number is

input to the computer system by using a portable barcode scanner or wand

reader. The wand has a scanning device that analyzes light & dark bars for

width & spacing. This wand reader is a special attachment to a video terminal.

Card Reading Devices

Time/Punch Card

IBM made the punch-card technology into the business standard of the

1950's and 1960's. There are manual punch card readers available. But now a

day this technology is not using widely.

Voice and Image Input Devices

Microphone

A microphone wants to take varying

pressure waves in the air and convert them into

varying electrical signals. There are five different

technologies commonly used to accomplish this

conversion:

Carbon microphones

The oldest and simplest microphone uses carbon dust. This is the

technology used in the first telephones and is still used in some telephones

today. The carbon dust has a thin metal or plastic diaphragm on one side. As

sound waves hit the diaphragm, they compress the carbon dust, which changes

its resistance. By running a current through the carbon, the changing resistance

changes the amount of current that flows.

Dynamic microphones

A dynamic microphone takes advantage of electromagnet effects. When

a magnet moves past a wire (or coil of wire), the magnet induces current to

flow in the wire. In a dynamic microphone, the diaphragm moves either a

magnet or a coil when sound waves hit the diaphragm, and the movement

creates a small current. Ribbon microphones - In a ribbon microphone, a thin

ribbon is suspended in a magnetic field. Sound waves move the ribbon which

changes the current flowing through it.

Condenser microphones

A condenser microphone is essentially a capacitor, with one plate of the

capacitor moving in response to sound waves. The movement changes the

capacitance of the capacitor, and these changes are amplified to create a

measurable signal. Condenser microphones usually need a small battery to

provide a voltage across the capacitor.

Crystal microphones

Certain crystals change their electrical properties as they change. By

attaching a diaphragm to a crystal, the crystal will create a signal when sound

waves hit the diaphragm.

Web Camera

A cam, home cam, or Webcam is a video camera, usually attached

directly to a computer, whose current or latest image is request able from a

Web site. A live cam is one that is continually providing new images that are

transmitted in rapid succession or, in some cases, in streaming video. Sites with

live cams sometimes embed them as Java applets in Web pages.

Cams have caught on; there are now (we estimate)

several thousand sites with cams. The first cams

were positioned mainly on fish tanks and coffee

machines. Many of today's live cams are on sex

oriented sites. For travel promotion, traffic information, and the

remote visualization of any ongoing event that's interesting, webcams seem like

an exciting possibility that will become more common as users get access to

more bandwidth.

OUTPUT DEVICESOUTPUT DEVICESOUTPUT DEVICESOUTPUT DEVICES

Monitors

Mono (Monochrome) – Display a single Color.

CGA - Color Graphic Adapter (4 Colors)

EGA – Enhance Graphic Adapter (16 Colors)

VGA – Video Gr. Ad. (16 colors & 256 shading)

SVGA – Super VGA

Printers

Impact Printers

The Print mechanism strikes against the paper.

Non Impact Printers

The Print mechanism does not strike against the ribbon or paper.

Character Printers

Speed in Characters per Second (CPS)

Used for low to medium volume applications

E.g.: Matrix, Ink Jet.

Line Printers

Speed in Lines per Minute (LPM)

Used for high volume medium quality applications.

E.g.: printing of public examination results.

Page Printers

Speed in Pages per Minute (PPM)

Used for medium to high volume, high quality applications.

E.g.: Print a master copy of a magazine by using a Laser Printer.

Color Printers

Color printers use a Color Cartridge. Time to

time you have to place the cartridge when the

cartridge is over.

Black and White Printers

Black and White Printers use a Black and White Cartridge. Time to time

you have to place the cartridge when the cartridge is over. There are printers

which supports both Color and Black and White cartridges.

Text Printers

To print text there are specially text printers. The quality is very low in

these printers.

Graphic Printers

These are very high quality printers. These printers are expensive than

normal printers. You can get very high quality Images printouts by using a

graphic printer.

Graphic designers and the people in studios use Graphic printers.

Dot Matrix Printers

The most widely used printer which prints one

character at a time. The technology has improved

during the recent past to include very high quality &

reasonably fast printers.

Daisy Wheel Printers

A kind of impact printer where the characters are arranged on the ends

of the spokes of a wheel (resembling the petals on a daisy).

The wheel (usually made of plastic) is rotated to select the character to

print and then an electrically operated hammer mechanism bends the selected

spoke forward slightly, sandwiching an ink ribbon between the character and

the paper, as in a typewriter.

One advantage of this arrangement over that of a typewriter is that

different wheels may be inserted to produce different typefaces.

Inkjet Printers

Ink printers work in much the same fashion as dot-matrix printers in that

they form images or characters with little dots. However,

the dots are formed, not by hammer like pins, but by

tiny droplets of ink, and the text these printers produce is of

letter quality. These printers can almost match the speed of dot- matrix printers

- up to about 270 eps-and they produce less noise.

Thermal Printers

Thermal printers use heat to produce an image

on special paper. The print mechanism - rather like a

dot - matrix print head - is designed to heat the

surface of chemically treated paper so that a dot is

produced based on the reaction of the chemical to the

heat. No ribbon or ink is involved. It can print multiple colors.

Laser Printers

Laser printer technology is much less mechanical than

impact printers resulting in much higher speeds and

quieter operation. The process resembles the operation

of a photocopy machine. A laser beam is directed across

the surface of a light-sensitive drum and fixed as needed

to record an image in the form of a pattern of tiny dots.

The image is then transferred to the paper. This printer prints a page at a

time - in the same fashion as a copying machine, using a special toner. When

high-speed laser printers (also called page printers) were introduced, they were

very expensive. However, recent laser printer technology has made desktop

versions available at very reasonable prices.

Plotters

A plotter is a specialized output device designed to produce high-quality

graphics in a variety of colors. Drum plotters and flat bed plotters both use pens

and electrostatic plotters do not.

Drum Plotter

The paper is mounted on the surface of a drum. The drum revolves and

the plotter pens (which are similar to felt-tip pens) are horizontally positioned

over the target area. When the paper has rotated to the correct point, the pens

are dropped to the surface moved left and right under program control across

the paper as the drum revolves. When the image is complete,

the pens are raised from the surface.

Flat Bed Plotter

These are designed so that the paper is placed flat and one or

more pens move horizontally and vertically across the paper.

Electrostatic Plotters

Use electrostatic charges to create images out of very small dots on

specially treated paper. Electrostatic plotters are faster than pen plotters and can

produce images of very high resolution, e.g.: Used by Architects, Surveyors,

and Engineers.

Voice Output Devices

Voice output should be a more

useful medium. This technology has

had to overcome many hurdles. The

most difficult has been that every

individual perceives speech

differently; that is, the voice patterns,

pitches, and reflections we can hear

and understand are different for all of us. It is not always easy to understand an

unfamiliar voice pattern. At this point, two different approaches to voice output

have evolved:

Speech coding

This relies on human speech as a reservoir of sounds to draw from in

building the words and phrases to be output. Sounds are codified and stored on

disk to be retrieved and translated back as sounds. Speech coding has been used

in applications such as automobiles, toys, and games.

Speech synthesis

In this method voice is produced electronically without the use of a

human voice. The largest application to date for the speech synthesis approach

to voice output converting text into “spoken” words has many potential uses,

including providing reading machines for the blind. And, of course, sound

output does not have to be in voice form, it can be music or special-effects

sounds, such as the sound accompaniment for computer animation, in cartoons

etc.

COM Devices

Serial port or "com port". A connector on a computer to which you can

attach a serial line connected to peripherals which communicate using a serial

(bit-stream) protocol.

The most common type of serial port is a 25-pin D-type connector

carrying EIA-232 signals. Smaller connectors (e.g. 9-pin D-type) carrying a

subset of EIA-232 are often used on personal computers. The serial port is

usually connected to an integrated circuit called a UART which handles the

conversion between serial and parallel data.

In the days before bit-mapped displays, and today on multi-user

systems, the serial port was used to connect one or more terminals

(teletypewriters or VDUs), printers, modems and other serial peripherals.

Two computers connected together via their serial ports, possibly via modems,

can communicate using a protocol such as UUCP or CU or SLIP.

CPU (CENTRAL PROCESSING UNIT)CPU (CENTRAL PROCESSING UNIT)CPU (CENTRAL PROCESSING UNIT)CPU (CENTRAL PROCESSING UNIT)

Processor

A processor is the logic circuitry that responds to

and processes the basic instructions that drive a

computer. The term processor has generally replaced

the term central processing unit (CPU). The processor

in a personal computer or embedded in small devices is often called a

microprocessor.

Arithmetic and Logic Unit

An arithmetic-logic unit (ALU) is the part of a computer processor

(CPU) that carries out arithmetic and logic operations on the operands in

computer instruction words. In some processors, the ALU is divided into two

units, an arithmetic unit (AU) and a logic unit (LU). Some processors contain

more than one AU - for example, one for fixed-point operations and another for

floating-point operations. (In personal computers floating point operations are

sometimes done by a floating point unit on a separate chip called a numeric

coprocessor.)

Typically, the ALU has direct input and output access to the processor

controller, main memory (random access memory or RAM in a personal

computer), and input/output devices. Inputs and outputs flow along an

electronic path that is called a bus. The input consists of an instruction word

(sometimes called a machine instruction word) that contains an operation code

(sometimes called an "op code"), one or more operands, and sometimes a

format code. The operation code tells the ALU what operation to perform and

the operands are used in the operation. (For example, two operands might be

added together or compared logically.) The format may be combined with the

op code and tells, for example, whether this is a fixed-point or a floating-point

instruction. The output consists of a result that is placed in a storage register

and settings that indicate whether the operation was performed successfully. (If

it isn't, some sort of status will be stored in a permanent place that is sometimes

called the machine status word.) In general, the ALU includes storage places

for input operands, operands that are being added, the accumulated result

(stored in an accumulator), and shifted results.

The flow of bits and the operations performed on them in the subunits of

the ALU is controlled by gated circuits. The gates in these circuits are

controlled by a sequence logic unit that uses a particular algorithm or sequence

for each operation code. In the arithmetic unit, multiplication and division are

done by a series of adding or subtracting and shifting operations. There are

several ways to represent negative numbers. In the logic unit, one of 16

possible logic operations can be performed - such as comparing two operands

and identifying where bits don't match. The design of the ALU is obviously a

critical part of the processor and new approaches to speeding up instruction

handling are continually being developed.

Control Unit

Control Unit controls every single hardware part attached to the

computer. Its main task is controlling the hardware devices which are attached

to the machine according to the signals of CPU.

LOGICAL STRUCTURE OF A COMPUTERLOGICAL STRUCTURE OF A COMPUTERLOGICAL STRUCTURE OF A COMPUTERLOGICAL STRUCTURE OF A COMPUTER

BACKING STORAGE

INTERNAL STORAGE OUTPUT

CONTROL UNIT

ARITHMETIC &

LOGICAL

UNIT.

INPUT

HOW COMPUTERS WORK?HOW COMPUTERS WORK?HOW COMPUTERS WORK?HOW COMPUTERS WORK?

Computers process information using the instructions from the user to

produce the desired results. The instruction that you feed in the computer,

through software, is the basic input. This input could be fed through a keyboard

or a mouse or a scanner, etc. These instructions are then sent to the processor

know as the central processing unit for processing. By processing, broadly we

mean carrying out of instructions for a task to be completed. After the task or

processing has been performed, the processor send, the result, know as the

output to the screen or the printer, as desired by you want to store the

information for any future use you can very well store it either on the hard disk

or any other storage device like floppy disk etc. the illusion, that follows makes

the whole procedure more clear.

BOOTING PROCESSBOOTING PROCESSBOOTING PROCESSBOOTING PROCESS

Booting the Computer

The PC boot process starts when a small program within the BIOS chip

looks for an active partition and loads the operating system. There are two

methods for booting a computer: cold and warm booting.

Cold Boot

Cold booting occurs when the computer’s power switch is turned on.

The effect of a cold boot is that it brings the system to the very beginning of the

boot process, beginning with the POST. This may become necessary when the

computer stops responding to any commands, including warm boots.

Warm Boot

A warm boot bypasses the first two system tests and goes directly to the

bootstrap loader (the point where DOS loads). A warm boot is triggered by

pressing the Ctrl, Alt, and Del keys at the same time.

CTRL + ALT + DEL

Rebooting the computer should be used only as a last resort. Any

information in open application files could be lost when rebooting takes place.

Creating Boot Disks

Every once in a blue moon your system may refuse to boot. There are

numerous reasons that could cause this. If you are prepared with an emergency

boot disk for such an occasion, you will save yourself a lot of anxious moments

The steps for preparing a boot disk are as follows:

1. Format a floppy disk using the IS switch. Put a blank diskette into your

floppy drive.

2. Type format A: /S

3. Copy the AUTOEXEC.BAT and CONFIG.SYS files to the newly

4. /S-formatted disk.

5. Copy any files and drivers that are essential to the boot process such as

IO.SYS, COMMAND.COM and other files necessary for your particular

system.

Label the disk appropriately and write protect it by flipping the black

switch on the bottom of the diskette. Store the disk in a safe and readily

accessible spot. By default, every time the computer is started, it searches in

drive A for a bootable floppy disk. In the event that the hard drive does not

boot, you are able to access the system from drive A. This allows you the

opportunity to look for the problem.

OPERATING SYSTEMOPERATING SYSTEMOPERATING SYSTEMOPERATING SYSTEM

Operating System Concepts

Many of the first operating systems were device dependent and

proprietary. A device dependent software product is one that runs only on a

specific type or make of computer. Proprietary software is privately owned and

limited to a specific vendor or computer model. When manufacturers

introduced a new computer or model, they

often produced an improved and different

proprietary operating system. Problems

arose, however, when a user wanted to

switch computer models or manufacturers.

The user’s application soft ware often

would not work on the new computer

because the applications were designed to

work with a specific operating system.

Some operating systems still are device dependent. The trend today,

however, is toward device- independent operating systems that run on

computers provided by a variety of manufacturers. The advantage of device-

independent operating systems is you can retain existing application software

and data files even if you change computer models or vendors. This feature

generally represents a sizable savings in time and money. New versions of an

operating system usually are downward compatible. A downward compatible

operating system is one that recognizes and works with application software

written for an earlier version of the operating system. The application software,

by contrast, is said to be upward compatible. An upward- compatible product is

written for an earlier version of the operating system, but also runs with the

new version. The three basic categories of operating systems that exist today

are stand-alone, network, and embedded. The table in Figure 8-18 lists names

of operating systems in each category. The following pages discuss the

operating systems listed in the table.

Stand-Alone Operating Systems

A stand-alone operating system is a complete operating system that works on a

desktop or notebook computer. Some stand-alone operating systems, called

client operating systems, also work in conjunction with a network operating

system. That is, client operating systems can operate with or without a network.

Examples of stand-alone operating systems are DOS, Windows 3.x, Windows

95, Windows NT Workstation, Windows 98, Windows 2000 Professional,

Windows Millennium Edition, Windows XP Home Edition, Windows XP

Professional Edition, Mac, OS X, OS/2 Warp Client, UNIX, and Linux. The

following paragraphs briefly discuss most of these operating systems. The

section that covers network operating systems discusses UNIX and Linux.

Loading an Operating System

The "boot" process comes from the term "boot strap". It is a play on the

concept of pulling one's self up by one's own boot straps. What actually

happens is that when the computer is powered up, the CPU runs the startup

code implanted in the system's ROM BIOS (Read Only Memory Basic Input

Output System). This startup program contains the code that tests the computer

and sets up the hardware for use.

Its last step is to load and run a program stored on the first sector of the first

drive. This is the master boot record (MBR), and the program is the master

boot program (MBP). The MBP looks to see where the primary partitions are

and which one is set as the active partition. The active partition has its own

boot record, and this contains a program designed to start the operating system

located on that partition. A partition boot record is usually referred to as the

partition root super block.

Popular Operating Systems

Stand-alone

� DOS

� Windows 3.x

� Windows 95

� Windows NT Workstation

� Windows 98

� Windows 2000 Professional

� Windows Millennium Edition

� Windows XP Home Edition

� Windows XP Professional Edition

� Mac OS X

� OS/2 Warp Client

� UNIX

� Linux

Network

� Netware

� Windows NT Server

� Windows 2000 Server

� Windows.NET Server

� OS/2 Wrap Server for E-business

� UNIX

� Linux

� Solaris

Embedded

� Windows CE

� Pocket PC 2002

� Palm OS

DOS (Disk Operating System)

The term DOS (Disk Operating System) refers to several single user operating

systems developed in the early 1980s for personal computers. The two more

widely used versions of DOS were PC-DOS and MS-DOS. Microsoft

Corporation developed both PC-DOS and MS-DOS. The functionality of these

two operating systems was essentially the same. The basic difference between

PC-DOS and MS-DOS was the type of computer on which they were installed.

Microsoft developed PC-DOS (Personal Computer DOS) for IBM, which in

turn installed and sold PC-DOS on its computers. At the same time, Microsoft

marketed and sold MS-DOS (Microsoft DOS) to makers of IBM-compatible

PCs.

DOS used a command-line interface when Microsoft first developed it. Later

versions included both command-line and menu-driven user interfaces, as well

as improved memory and disk management. At its peak, DOS was a widely

used operating system, with an estimated 70 million computers running it.

Today, DOS no longer is widely used because it does not offer a graphical user

interface (GUI) and it cannot take full advantage of modern 32-bit personal

computer processors.

Windows 98

Microsoft developed an upgrade to the Windows 95 operating system, called

Windows 98. The Windows 98 operating system was more integrated with the

Internet than Windows 95. For example, Windows 98 included Microsoft

Internet Explorer, a popular Web browser. The Windows 98 file manager,

called Windows Explorer, and also had a Web browser look and feel. With

Windows 98, you could have an Active Desktop interface, which allowed you

to set up Windows so icons on the desktop and file names in Windows

Explorer worked similar to Web Links.

Windows 98 also provided faster system startup and shutdown, better file

management, and support for multimedia technologies such as DVD and

WebTV™ (today known as MSN® TV). Windows 98 supported USB, so you

easily could add and remove devices in your computer.

Windows NT

Windows NT Workstation

Microsoft developed Windows NT Workstation as a client operating system

that could connect to a Windows NT Server. Windows NT, also referred to as

NT, was an operating system designed for client! Server networks. Windows

NT Workstation had a Windows 95 interface. Thus, users familiar with

Windows 95 easily could migrate to Windows NT Workstation. Businesses

most often used Windows NT Workstation.

Windows NT Server

As previously mentioned, Microsoft developed Windows NT as an operating

system for client/server networks. The server in this environment used

Windows NT Server. The client computers used Windows NT Workstation or

some other stand-alone version of Windows.

Start and Login

In order to get your computer to work you need both hardware and software.

An operating system is software that you use in order to communicate with the

computer’s hardware such as the mouse, the keyboard and the computer’s

memory. Your computer must have the operating system software installed

before you can perform any operations. The operating system automatically

starts when you switch on the computer. The startup process is called booting.

Most operating systems provide built-in security, which ensures that only

authenticated users can access the computer. Thus whenever you start your

computer you must provide your valid user name and password. This attempt is

known as “logging on” and the entire process of verification is known as the

“logon process”. This process helps to protect your documents from

unauthorized users.

1. Switch on the computer (The “Welcome to Windows” screen will be

displayed)

2. Press Ctrl+Alt+Delete to open the “Log On to Windows” dialog box

3. In the “User Name” box, enter your user name

4. In the “Password” box, enter your password

5. Click OK

Use Mouse (Buttons)

The mouse is an input device you can use to perform various tasks such as

opening applications, selecting items, copying data, and moving data. The

mouse moves on a flat surface, usually a mouse pad. As you move the mouse, a

mouse pointer moves in the same direction on the screen. By default, the left

mouse button is the primary mouse button. You use the left mouse button for

selecting, moving and opening objects. If you are a left hander you may

configure the right mouse button as the primary mouse button if you need to.

The following table shows the mouse actions and how to perform them with

the left mouse button as the primary button.

Mouse Action How

Point Place the mouse pointer over an object.

Click Press and release the left mouse button.

Double Click Press and release the left mouse button two times in

rapid succession.

Drag While holding down the left mouse button, move the pointer

to your desired location, and then release the button.

Right Click Press and release the right mouse button.

Pointing

Place the mouse pointer over an object

Clicking

Press and release the left mouse button.

Dragging

While holding down the left mouse button, move the pointer to your desired

location, and then release the button.

Use Keyboard (Special Keys for Windows)

The key board is the most often used input device. There are some special keys

on the keyboard that will allow you to perform some frequent tasks.

Some of those are listed below.

1. The windows key: To open the start menu

2. Ctrl+Esc: To open the start menu

3. Ctrl+C: To copy a selected item

4. Ctrl+X: To cut a selected item

5. Ctrl+V: To paste a selected item

6. Ctrl+P: To print

7. The Caps Lock: To change case

8. Alt+F4: To close the current window/ Exit/ Shut Down

Shutting Down Your Computer

1. Click on the Start Button

2. Select Shut Down

3. Select OK

SYSTEM SOFTWARESYSTEM SOFTWARESYSTEM SOFTWARESYSTEM SOFTWARE

Computer Software

Software, also called a computer program or simply a program, is a

series of instructions that tells the hardware of a computer what to do. Some

instructions allow you to input data from the keyboard and direct the computer

to store the data in memory. Other instructions cause data in memory to be

used in calculations such as adding a series of numbers to obtain a total. Some

instructions compare two values in memory and direct the computer to perform

alternative operations based on the results of the comparison. Other instructions

direct the computer to print a report, display information on the monitor, draw

a color picture on the monitor, or store information on a disk.

A computer carries out, or executes, the instructions in a pro gram by

first placing, or loading, the instructions into the memory of the computer.

Usually, the computer loads the instructions from storage into memory. For

example, each time a program executes, it might load from the hard disk into

memory.

When you purchase a program, you typically receive media such as a -

CD-ROM(s) or a DYD-ROM that contains the software. Some programs can

load into memory directly from the media. With other programs, you must

install a part or all of the soft ware on the computer’s hard disk before you can

use the program. Some programs also require you to insert the media, such as a

CD-ROM, into the drive while you use, or run, the program. Others do not.

This program requires a CD-ROM in the CD-ROM drive. When you buy a

computer, it usually has some software pre installed on its hard disk. This

enables you to use the computer as soon as you set it up. Software is the key to

productive use of computers. With the proper software, a computer can become

a valuable tool. The two categories of software are system software and

application software. The following pages describe these categories of

software.

System Software

System software consists of the programs that control the operations of

the computer and its devices. System software serves as the interface between

the user, the application software, and the computer’s hard ware. Two types of

system software are the operating system and utility programs.

Operating System

An operating system (OS) is a set of programs containing instructions

that coordinate all the activities among computer hardware devices. The

operating system also contains instructions that allow you to run application

software. Many of today’s computers use Microsoft’s most recent operating

system, called Windows XP. When you start a computer, the operating system

loads into memory from the computer’s hard disk. It remains in memory while

the computer is running and allows you to communicate with the computer and

other software.

Utility Programs

A utility program is a type of system soft ware that performs a specific

task, usually related to managing a computer, its devices, or its programs. An

example of a utility program is an uninstaller, which removes a program that

has been installed on a computer. Most operating systems include several

utility programs for managing disk drives, printers, and other devices. You also

can buy stand-alone utility programs, which allow you to perform additional

computer management functions.

Language Translators

The programs written by using a computer programming language

should be converted to the machine code in order to run the program correctly

and to get the wanted output. Computer programming languages are in human

understandable for mat and machine code cannot be understood by human.

Converting Human readable format computer programs in to machine readable

format is done by Language Translators.

Translators we can basically divide in to two parts called Compilers and

Interpreters. The main difference between these two is the way that they

convert the Computer programming language to machine language.

Compiler

A compiler is a special program that processes statements written in a

particular programming language and turns them into machine language or

"code" that a computer's processor uses. Typically, a programmer writes

language statements in a language such as Pascal or C one line at a time using

an editor. The file that is created contains what are called the source statements.

The programmer then runs the appropriate language compiler, specifying the

name of the file that contains the source statements.

When executing (running), the compiler first parses (or analyzes) all of

the language statements syntactically one after the other and then, in one or

more successive stages or "passes", builds the output code, making sure that

statements that refer to other statements are referred to correctly in the final

code. Traditionally, the output of the compilation has been called object code

or sometimes an object module. (Note that the term "object" here is not related

to object-oriented programming.) The object code is machine code that the

processor can process or "execute" one instruction at a time. More recently, the

Java programming language, a language used in object-oriented programming,

has introduced the possibility of compiling output (called byte code) that can

run on any computer system platform for which a Java virtual machine or byte

code interpreter is provided to convert the bytecode into instructions that can be

executed by the actual hardware processor. Using this virtual machine, the

bytecode can optionally be recompiled at the execution platform by a just-in-

time compiler. Traditionally in some operating systems, an additional step was

required after compilation - that of resolving the relative location of

instructions and data when more than one object module was to be run at the

same time and they cross-referred to each other's instruction sequences or data.

This process was sometimes called linkage editing and the output known as a

load module.

A compiler works with what are sometimes called 3GL and higher-level

languages . An assembler works on programs written using a processor's

assembler language.

Interpreter

An interpreter is a computer program that executes other programs. This

is in contrast to a compiler which does not execute its input program (the

source code) but translates it into executable machine code (also called object

code) which is output to a file for later execution. It may be possible to execute

the same source code either directly by an interpreter or by compiling it and

then executing the machine code produced.

It takes longer to run a program under an interpreter than to run the

compiled code but it can take less time to interpret it than the total required to

compile and run it. This is especially important when prototyping and testing

code when an editinterpret-debug cycle can often be much shorter than an edit-

compile-run-debug cycle. Interpreting code is slower than running the

compiled code because the interpreter must analyze each statement in the

program each time it is executed and then perform the desired action whereas

the compiled code just performs the action. This run-time analysis is known as

"interpretive overhead". Access to variables is also slower in an interpreter

because the mapping of identifiers to storage locations must be done repeatedly

at run-time rather than at compile time.

DBMS Software

A database is a collection of data organized in a manner that allows

access, retrieval, and use of that data. In a manual database, you might record

data on paper and store it in a filing cabinet. With a computerized database, the

computer stores the data in an electronic format on a storage medium such as a

floppy disk or hard disk. Database software, also called a database management

system (DBMS), is software that allows you to create, access, and manage a

database. Using database software, you can add, change, and delete data in the

database; sort and retrieve data from the database; and create forms and reports

using the data in the database.

APPLICATION SOFTWAREAPPLICATION SOFTWAREAPPLICATION SOFTWAREAPPLICATION SOFTWARE

Application Software

Application software consists of programs that perform specific tasks for

users. Popular application software includes word processing software,

spreadsheet software, data base software, and presentation graphics software.

Word processing software allows you to create documents such as letters,

memorandums, and brochures. Spreadsheet software allows you to calculate

numbers arranged in rows and columns. Users perform financial tasks such as

budgeting and forecasting with spreadsheet software. Database soft ware

allows you to store data in an organized fashion, as well as retrieve,

manipulate, and display that data in a variety of formats. With presentation

graphics software, you create documents called slides that add visual appeal to

presentations. Software vendors often bundle and sell these four applications

together as a single unit. This bundle, called a suite, costs much less than if you

purchased the applications individually. Microsoft’s Office XP is a very

popular suite.

Many other types of application software exist that enable users to

perform a variety of tasks. Some widely used applications include the

following: reference, education, and entertainment; desktop publishing; photo

and video editing; multimedia authoring; network, communications, electronic

mail (e-mail), and Web browsers; accounting; project management; and

personal information management. Application software is available in a

variety of forms: packaged, custom, freeware, public domain, shareware, and

from application service providers.

Word Processing

� Microsoft Word

� Corel WordPerfect

� Lotus Word Pro

� Microsoft Pocket Word

Spread Sheet

� Microsoft Excel

� Corel Quattro Pro

� Lotus 123

� Microsoft Pocket Excel

Database

� Microsoft Access

� Corel Paradox

� Lotus Approach

� Microsoft Visual FoxPro

� Oracle

Presentation Graphics

� Microsoft PowerPoint

� Corel Presentations

� Lotus Freelance Graphics

Personal Information Manager

� Microsoft Outlook

� Corel CENTRAL

� Lotus Organizer

� Palm Multi Mail

Software Suite

� Microsoft Office

� Corel WordPerfect Office

� Lotus SmartSuite

Project Management

� Microsoft Project

� Primavera Sure Track Project Manager

Accounting

� Intuit QuickBooks

� Peachtree Col11plete Accounting

� Tally

Application Packages

Copyrighted application or system software that meets the needs of a

wide variety of users, not just a single user or company, is called packaged

software. You can purchase packaged software from stores that sell computer

products. You also can purchase packaged software from companies on the

Internet.

Custom-Made Software

Sometimes a user or company with unique soft ware requirements

cannot find packaged software that meets all its needs. In this case, the person

or company can opt for custom software. Custom software, written by a

programmer, is a tailor-made application or system program developed at a

user’s request to perform specific functions.

Freeware in Public-Domain

Software and Shareware

Freeware is application or system software provided at no cost to a user

by an individual or a company. Freeware is copyrighted. You cannot resell it as

your own. Public- domain software also is free software, but it has been

donated for public use and has no copyright restrictions. Shareware is

copyrighted software that is distributed free for a trial period. If you want to

use a shareware program beyond that period, you send a payment to the person

or company that developed the program. Companies that develop shareware

rely on the honor system. The company trusts you to send payment if you

continue to use the software beyond the stated trial period. Upon sending this

small fee, the developer registers you to receive service assistance and updates.

Examples of shareware, freeware, and public-domain software include

utility programs, graphics programs, and games. Thousands of these pro grams

are available on the Internet to download, or copy to your computer. You also

can obtain copies of these programs from the developer, a coworker, or a

friend.

Application Service Provider

Storing and maintaining programs can be a costly investment for individuals

and businesses. Some opt to use an application service provider for their

software needs. An application service provider (ASP) is a third-party company

that manages and distributes software and services on the Internet. That is,

instead of installing the software on your computer, you run the programs from

the Internet. Some vendors pro vide access to the software at no cost. Others

charge for use of the program.

INTRODUCTION TO COMPUTER VIRUSESINTRODUCTION TO COMPUTER VIRUSESINTRODUCTION TO COMPUTER VIRUSESINTRODUCTION TO COMPUTER VIRUSES

A virus is a piece of programming code usually disguised as something

else that causes some unexpected and usually undesirable event. A virus is

often designed so that it is automatically spread to other computer users.

Viruses can be transmitted as attachments to an e-mail note, as downloads, or

be present on a diskette or CD. The source of the e-mail note, downloaded file,

or diskette you've received is often unaware of the virus. Some viruses wreak

their effect as soon as their code is executed; other viruses lie dormant until

circumstances cause their code to be executed by the computer. Some viruses

are playful in intent and effect ("Happy Birthday, Ludwig!") and some can be

quite harmful, erasing data or causing your hard disk to require reformatting.

Generally, there are three main classes of viruses:

Boot Sector

These viruses infect executable code found in certain system areas on a

disk. They attach to the DOS boot sector on diskettes or the Master Boot

Record on hard disks.

A typical scenario (familiar to the author) is to receive a diskette from an

innocent source that contains a boot disk virus. When your operating system is

running, files on the diskette can be read without triggering the boot disk virus.

However, if you leave the diskette in the drive, and then turn the computer off

or reload the operating system, the computer will look first in your A drive,

find the diskette with its boot disk virus, load it, and make it temporarily

impossible to use your hard disk. (Allow several days for recovery.) This is

why you should make sure you have a bootable floppy.

File

Some file infector viruses attach themselves to program files, usually

selected .COM or .EXE files. Some can infect any program for which

execution is requested, including .SYS, .OVL, .PRG, and .MNU files. When

the program is loaded, the virus is loaded as well. Other file infector viruses

arrive as wholly-contained programs or scripts sent as an attachment to an e-

mail note.

Trojan Horse

Trojan horse attacks pose one of the most serious threats to computer

security. If you were referred here, you may have not only been attacked but

may also be attacking others unknowingly. This page will teach you how to

avoid falling prey to them, and how to repair the damage if you already did.

According to legend, the Greeks won the Trojan war by hiding in a huge,

hollow wooden horse to sneak into the fortified city of Troy. In today's

computer world, a Trojan horse is defined as a "malicious, security-breaking

program that is disguised as something benign". For example, you download

what appears to be a movie or music file, but when you click on it, you unleash

a dangerous program that erases your disk, sends your credit card numbers and

passwords to a stranger, or lets that stranger hijack your computer to commit

illegal denial of service attacks like those that have virtually crippled the

DALnet IRC network for months on end.

The following general information applies to all operating systems, but

by far most of the damage is done to/with Windows users due to its vast

popularity and many weaknesses.

(Note: Many people use terms like Trojan horse, virus, worm, hacking

and cracking all interchangeably, but they really don't mean the same thing. If

you're curious, here's a quick primer defining and distinguishing them. Let's

just say that once you are "infected", Trojans are just as dangerous as viruses

and can spread to hurt others just as easily!)

Methods of Activation

You can open a file by double clicking on it, but you can’t see the

behind process.

Most of the times these files can be .exe files which are in floppy

diskettes or in Compact Disks.

You might have down load something from the internet which you don’t

trust 100%.

You might open Email attachments without knowing.

Virus Effects

If your computer is running down slowly more than earlier. If the

machine shut downs abnormally. If you can see unknown files or folders have

been saved in to the hard disk. If anything abnormally happens in your machine

than earlier it might be to a virus effect.

Preventive Steps

1. Above all check every data medium you get. Even if it belongs to your best

friend, it does not give you the guarantee of security. It concerns not only

floppy disks, but also CD-ROMs, CD-RWs and ZIPs. Do not even open

floppy disk if you get it from an unknown person. Every data medium

obtained from an anonymous source is potentially infected.

2. Block the possibility of system boot from a floppy disk. Most of the latest

BIOSes have a function, which enables to do it. In that simple way you can

avoid the risk of having your computer infected by boot-sector viruses.

3. Do not open any letter with attached files received from an unknown

sender.

4. Do not run macros in documents of office packages if an anti-virus monitor

is off.

5. Use an anti-virus monitor working constantly at the background. For the

best security the monitor should check the incoming mail and every file

downloaded from the Internet.

6. You should systematically update definitions of viruses used by anti-virus

software. Updating should be done at least once a month (the best once a

week).

7. In a situation when you chat in the Internet (especially using mIRC) you

have to follow the same rules as in case of received e-mails. Do not open

any received files, if you do know who sent it to you and why. Some

viruses are sent automatically, so same information about sender does not

give you guarantee of security.

8. NEVER download blindly from people or sites which you aren't 100% sure

about. In other words, as the old saying goes, don't accept candy from

strangers. If you do a lot of file downloading, it's often just a matter of time

before you fall victim to a Trojan.

9. Even if the file comes from a friend, you still must be sure what the file is

before opening it, because many trojans will automatically try to spread

themselves to friends in an email address book or on an IRC channel. There

is seldom reason for a friend to send you a file that you didn't ask for. When

in doubt, ask them first, and scan the attachment with a fully updated anti-

virus program.

10. Beware of hidden file extensions! Windows by default hides the last

extension of a file, so that innocuous-looking "susie.jpg" might really be

"susie.jpg.exe" - an executable Trojan! To reduce the chances of being

tricked, unhide those pesky extensions.

11. NEVER use features in your programs that automatically get or preview

files. Those features may seem convenient, but they let anybody send you

anything which is extremely reckless. For example, never turn on "auto

DCC get" in mIRC, instead ALWAYS screen every single file you get

manually. Likewise, disable the preview mode in Outlook and other email

programs.

12. Never blindly type commands that others tell you to type, or go to web

addresses mentioned by strangers, or run pre-fabricated programs or scripts

(not even popular ones). If you do so, you potentially trust a stranger with

control over your computer, which can lead to Trojan infection or other

serious harm.

13. Don't be lulled into a false sense of security just because you run anti-virus

programs. Those do not protect perfectly against many viruses and trojans,

even when fully up to date. Anti-virus programs should not be your front

line of security, but instead they serve as a backup in case something sneaks

onto your computer.

14. Finally, don't download an executable program just to "check it out" - if it's

a Trojan, the first time you run it, you're already infected!

Introduction to Anti-virus Software

Antivirus (or "anti-virus") software is a class of program that searches

your hard drive and floppy disks for any known or potential viruses. The

market for this kind of program has expanded because of Internet growth and

the increasing use of the Internet by businesses concerned about protecting

their computer assets.

Following are some URLs where you can find more information about

antivirus software.

International Computer Security Association

http://www.icsa.net

Virus Bulletin

http://www.virusbtn.com

Dr Salomon's page

http://www.drsalomon.com

CERT - Computer Emergency Response Team

http://www.cert.org

McAfee anti-virus

http://vil.mcafee.com

Symantec

http://www.symantec.com/avcenter/

Other pages about virus:

http://www.mks.com.pl

http://www.antywirusy.pl

http://www.wirusy.pl

http://www.wirusy.onet.pl

http://www.viruslist.com

Norton

Antivirus software by Symantec that scans and cleans instant-message

attachments as well as email messages, and removes them automatically. You

can download 15 day trial version freely from the Symantec website.

McAfee

Anti-virus software by MacAfee Co. Scan and restores your PC

immediately. Detects Spy ware, blocks worms/unsafe scripts.

Virus Checking

Once you install the Virus guard it will automatically scan your system.

When you boot up the machine and until you shut down the system it will be

scanning your system behind other processes.

When you insert a unknown floppy diskette its better to scan the diskette

for viruses.

You can right click on the floppy drive and select scan for viruses or

open the anti virus program and select scan and then select floppy diskette.

Then it will remove the infected files from the particular files and if it is

not possible it asks to delete the infected files. It’s better to delete the infected

files permanently if the recovery is not possible.

Disinfection

Computer viruses can be stored on floppy disks, hard disks, and even in

the memory of a computer. Viruses frequently move from one computer to

another on floppy disks or via files attached to email messages.

Most viruses can be detected and removed using virus detection

software such as McAfee VirusScan. In Nebula, we configure this package to

be loaded at startup and watch for any signs of viruses. If Mc Afee VirusScan

detects a virus in a file you're working with, it will notify you and give you

some basic instructions on what to do next. You can also check the list below

for instructions on dealing with some of the more pervasive virus infections. If

you get a virus, you should always notify the person who gave you the file, by

telephone if possible, so they can get rid of it on their computer, too.

What you need to know

• Any email claiming to be a Microsoft update is actually a virus itself; delete

the file and do not click on any attachment(s).

• Any email from another person claiming that you have a virus is most

probably a virus hoax (see the Nebula virus hoax page for more

information).

• Do not delete files from your system based on an email message; check the

hoax page for more information.

• The most reliable source of information about a virus infection will come

from your computer's McAfee program. If this tells you that you have a

virus, do notify Nebula Support.

• Do not open unknown attachments, ever.

Immunization

Viruses remain a significant threat to modern networked computer

systems. Despite the best efforts of those who develop anti-virus systems, new

viruses and new types of virus that are not dealt with by existing protection

schemes appear regularly. In addition, the rate at which a virus can spread has

risen dramatically with the increase in connectivity. Defenses against infections

by known viruses rely at present on immunization yet, for a variety of reasons,

immunization is often only effective on a subset of the nodes in a network and

many nodes remain unprotected. Little is known about either the way in which

a viral infection proceeds in general or the way that immunization affects the

infection process. We present the results of a simulation study of the way in

which virus infections propagate through certain types of network and of the

effect that partial immunization has on the infection. The key result is that

relatively low levels of immunization can slow an infection significantly.

Removing

If you are not sure if your computer is virus-free, try removing a virus

from the hard disk as described below.

1. Shut down your machine, then start it up and log in; this ensures you have

the latest virus update files on your system.

2. Choose Start - Programs - Network Associates - Virus Scan to begin a virus

scan on your computer.

3. In the box labeled "Scan in", make sure the drive you wish to search for

viruses is selected, typically C: If it isn't, click "Browse" and choose the

right drive (and folder, if desired). Do not scan the I:\groups or H: drives;

they are scanned regularly by the engineers.

4. Note that the "Include subfolders" checkbox should be selected, so Virus

Scan looks through all subdirectories of the location you've chosen.

5. Note also that by default only program files are scanned; this includes Word

and Excel document files. If you wish to scan all files, click the "All files"

radio button.

6. Click "Scan Now" to start the search.

7. If a virus is found, click on the file name and choose Clean Infected Files.

8. If Virus Scan reports that it cannot clean a file, close the box and restart

your computer. Then repeat the scan. If Virus Scan repeats the report,

contact Nebula Support. If possible, use the Nebula Support icon on your

desktop; this will include other information about your system that may

help to solve the problem.

9. Remember, don't respond to an email telling you that you have a virus. It's

either a hoax (in which case you just get more spam now that they know

your address is valid), or a response to an infected message that only looks

like it came from you--the latest viruses disguise their "From" addresses.

Creation of a Rescue Disk

We can call rescue disk as a boot disk. Rescue disk or Boot disk can be

used in a situation where the computer does not boot in the normal way. This

abnormal condition is can be due to a virus effect.

You can follow the following instructions to create a boot disk in

Windows XP.

• Insert a 3 ½’ floppy diskette in to your machine.

• Double Click on My Computer Icon on the desktop.

• Right Click on Floppy Diskette Drive.

• Select Format

• Select Create MSDOS Startup Disk

• Click on Start to create the Disk.

Installing Anti-virus Software

To install the antivirus soft ware first you have to buy a CD or download it

from a website. As an example we’ll see how to install Norton Antivirus.

First you select the setup file and double click on it.

Then it will prompt you:

You have to click on Yes and then it will start to scan all the files in your

machine.

It will scan all the files and if there is any virus infected file it will show you.

When the scanning is complete it will show you a report.

Then the setup will continue to install the software.

After clicking Next button you have to read the software license agreement and

accept the agreement to proceed.

If you don’t accept the agreement setup will stop.

Then it will ask for the path of the destination folder where the software files

will be saved.

After selecting the correct path and folder it will show you where the software

will be installed. To proceed and install the software to your system you have

to click on the Next button.

Then you can see the progress of the installation.

After coping the installation files in to your hard drive it will show you the

Read me text file. The Readme.txt file contains the details about the product.

Click Next to proceed.

You will get this message if the setup has been successfully installed.

Click on Finish to finish installing the software.

After you install the software you have to register the product.

We are going to use the trial version. If you want you can purchase the product

online, or if you have already purchased you have to enter the product key

which you will receive after purchasing the original product.

Then it will display you a summary of tasks which the software will operate on.

You can do wanted modifications.

Click on Finish to finish the configuration.

Upgrading Anti-virus Software

Once you install the antivirus software it’s a must that you upgrade the

software frequently. You can do it online.

If your antivirus is not up to date then it will show you the following message.

After upgrading the automatic System Scan will run.

If you want you can stop the scan now and do it later.

After the scan it will give you a summary.

You can see whether the system scan is running in the background and its

configuration.

Uninstalling Anti-virus Software

If you feel that you need better antivirus software you can uninstall the current

antivirus software and install a new one.

We’ll see how to uninstall the current antivirus software.

You can go to the control panel and select Add/Remove Programs.

Then select Norton antivirus 2004 and click on Remove.

Then it will display:

You can click on Remove All.

Then it will warn you that this will remove antivirus software from your

system. You have to click on Next to proceed.

Then you can see the uninstallation progress.

After finishing the uninstallation it will ask to restart the machine.

You can select any option and click on Finish to finish the uninstallation.

PRIMARY STORAGEPRIMARY STORAGEPRIMARY STORAGEPRIMARY STORAGE

RAM

RAM (random access memory) is the place in a computer where the

operating system, application programs, and data in current use are kept so that

they can be quickly reached by the computer's processor. RAM is much faster

to read from and write to than the other kinds of storage in a computer, the hard

disk, floppy disk, and CD-ROM. However, the data in RAM stays

there only as long as your computer is running. When you

turn the computer off, RAM loses its data. When you

turn your computer on again, your operating system

and other files are once again loaded into RAM,

usually from your hard disk.

RAM can be compared to a person's short-term

memory and the hard disk to the long-term memory. The

short-term memory focuses on work at hand, but can

only keep so many facts in view at one time. If short-term memory fills up,

your brain sometimes is able to refresh it from facts stored in long-term

memory. A computer also works this way. If RAM fills up, the processor needs

to continually go to the hard disk to overlay old data in RAM with new,

slowing down the computer's operation. Unlike the hard disk which can

become completely full of data so that it won’t accept any more, RAM ever

runs out of memory. It keeps operating, but much more slowly than you may

want it to.

How Big is RAM?

RAM is small, both in physical size (it's stored in microchips) and in the

amount of data it can hold. It's much smaller than your hard disk. A typical

computer may come with 256 million bytes of RAM and a hard disk that can

hold 40 billion bytes. RAM

comes in the form of "discrete"

(meaning separate)

microchips and also in the form

of modules that plug into holes

in the computer's motherboard.

These holes connect through a bus or

set of electrical paths to the processor. The hard drive,

on the other hand, stores data on a magnetized

surface that looks like a phonograph record.

Most personal computers are designed to allow you to add additional

RAM modules up to a certain limit. Having more RAM in your computer

reduces the number of times that the computer processor has to read data in

from your hard disk, an operation that takes much longer than reading data

from RAM. (RAM access time is in nanoseconds; hard disk access time is in

milliseconds.)

Why Random Access?

RAM is called "random access" because any storage location can be

accessed directly. Originally, the term distinguished regular core memory from

offline memory, usually on magnetic tape in which an item of data could only

be accessed by starting from the beginning of the tape and finding an address

sequentially. Perhaps it should have been called "inconsequential memory"

because RAM access is hardly random.

RAM is organized and controlled in a way that enables data to be stored

and retrieved directly to specific locations. A term IBM has preferred is direct

access storage or memory. Note that other forms of storage such as the hard

disk and CDROM are also accessed directly (or "randomly") but the term

random access is not applied to these forms of storage.

In addition to disk, floppy disk, and CD-ROM storage, another

important form of storage is read-only memory (ROM), a more expensive kind

of memory that retains data even when the computer is turned off. Every

computer comes with a small amount of ROM that holds just enough

programming so that the operating system can be loaded into RAM each time

the computer is turned on.

ROM

ROM is "built-in" computer memory containing data that normally can

only be read, not written to. ROM contains the programming that allows your

computer to be "booted up" or regenerated each time you turn it on. Unlike a

computer's random access memory (RAM), the data in ROM is not lost when

the computer power is turned off. The ROM is sustained by a small long-life

battery in your computer. If you ever do the hardware setup procedure with

your computer, you effectively will be writing to ROM.

PROM

Programmable read-only memory (PROM) is read-only memory (ROM)

that can be modified once by a user. PROM is a way of allowing a user to tailor

a microcode program using a special machine called a PROM programmer.

This machine supplies an electrical current to specific cells in the ROM that

effectively blows a fuse in them. The process is known as burning the PROM.

Since this process leaves no margin for error, most ROM chips designed to be

modified by users use erasable programmable read-only memory (EPROM) or

electrically erasable programmable read-only memory (EEPROM).

EPROM

EPROM (erasable programmable read-only memory) is programmable

read-only memory (programmable ROM) that can be erased and re-used.

Erasure is caused by shining an intense ultraviolet light through a window that

is designed into the memory chip. (Although ordinary room lighting does not

contain enough ultraviolet light to cause erasure, bright sunlight can cause

erasure. For this reason, the window is usually covered with a label when not

installed in the computer.)

A different approach to a modifiable ROM is electrically erasable

programmable read-only memory (EEPROM).

EEPROM

EEPROM (electrically erasable programmable read-only memory) is

user-modifiable read-only memory (ROM) that can be erased and

reprogrammed (written to) repeatedly through the application of higher than

normal electrical voltage. Unlike EPROM chips, EEPROMs do not need to be

removed from the computer to be modified. However, an EEPROM chip has to

be erased and reprogrammed in its entirety, not selectively. It also has a limited

life - that is, the number of times it can be reprogrammed is limited to tens or

hundreds of thousands of times. In an EEPROM that is frequently

reprogrammed while the computer is in use, the life of the EEPROM can be an

important design consideration. A special form of EEPROM is flash memory,

which uses normal PC voltages for erasure and reprogramming.

Cache

A cache (pronounced CASH) is a place to store something temporarily.

The files you automatically request by looking at a Web page are stored on

your hard disk in a cache subdirectory under the directory for your browser (for

example, Internet Explorer). When you return to a page you've recently looked

at, the browser can get it from the cache rather than the original server, saving

you time and the network the burden of some additional traffic. You can

usually vary the size of your cache, depending on your particular browser.

Computers include caches at several levels of operation, including cache

memory and a disk cache. Caching can also be implemented for Internet

content by distributing it to multiple servers that are periodically refreshed.

(The use of the term in this context is closely related to the general concept of a

distributed information base.)

Altogether, we are aware of these types of caches:

• International, national, regional, organizational and other "macro"

caches to which highly popular information can be distributed and

periodically updated and from which most users would obtain

information.

• Local server caches (for example, corporate LAN servers or access

provider servers that cache frequently accessed files). This is similar to

the previous idea, except that the decision of what data to cache may be

entirely local.

• Your Web browser's cache, which contains the most recent Web files

that you have downloaded and which is physically located on your hard

disk (and possibly some of the following caches at any moment in time)

• A disk cache (either a reserved area of RAM or a special hard disk

cache) where a copy of the most recently accessed data and adjacent

(most likely to be accessed) data is stored for fast access.

• RAM itself, which can be viewed as a cache for data that is initially

loaded in from the hard disk (or other I/O storage systems).

• L2 cache memory, which is on a separate chip from the microprocessor

but faster to access than regular RAM.

• L1 cache memory on the same chip as the microprocessor.

SECONDARY STORAGESECONDARY STORAGESECONDARY STORAGESECONDARY STORAGE

Secondary storage is all addressable data storage that is not currently in

the computer's main storage or memory. Synonyms are external storage and

auxiliary storage.

Floppy Disks

A diskette is a random access, removable data storage medium that can

be used with personal computers. The term usually refers to the magnetic

medium housed in a rigid plastic cartridge measuring 3.5 inches square

and about 2 millimeters thick. Also called a

"3.5-inch diskette," it can store up to 1.44

megabytes (MB) of data. Although many

personal computers today come with a 3.5-

inch diskette drive preinstalled, some

notebook computers and centrally-

administered desktop computers omit them.

Some older computers provide drives for magnetic diskettes

that are 5.25 inches square, about 1 millimeter thick, and capable of holding 1.2

megabytes of data. These were sometimes called "floppy disks" or "floppies"

because their housings are flexible. In recent years, 5.25-inch diskettes have

been largely replaced by 3.5-inch diskettes, which are physically more rugged.

Many people also call the newer hard cased diskette a "floppy." Magnetic

diskettes are convenient for storing individual files and small programs.

However, the magneto-optical (MO) disk is more popular for mass storage,

backup, and archiving. An MO diskette is only a little larger, physically, than a

conventional 3.5-inch magnetic diskette. But because of the sophisticated

read/write technology, the MO diskette can store many times more data.

Disk Drives

Hard Disks

A hard disk is part of a unit, often called a "disk drive," "hard drive," or

"hard disk drive," that store and provides relatively quick access to large

amounts of data on an electromagnetically charged surface or set of surfaces.

Today's computers typically come with a hard disk that contains several billion

bytes (gigabytes) of storage.

A hard disk is really a set of stacked "disks," each of which, like

phonograph records, has data recorded electromagnetically in concentric circles

or "tracks" on the disk. A "head" (something like a phonograph arm but in a

relatively fixed position) records (writes) or reads the information on the tracks.

Two heads, one on each side of a disk, read or write the data as the disk spins.

Each read or write operation requires that data be located, which is an operation

called a "seek." (Data already in a disk cache, however, will be located more

quickly.)

A hard disk/drive unit comes with a set rotation speed varying from

4500 to 7200 rpm. Disk access time is measured in milliseconds. Although the

physical location can be identified with cylinder, track, and sector locations,

these are actually mapped to a logical block address (LBA) that works with the

larger address range on today's hard disks.

Top view of a 36 GB, 10,000 RPM, IBM SCSI server hard disk, with its top

cover removed. Note the height of the drive and the 10 stacked platters. (The

IBM Ultra star 36ZX.)

Optical Disks

An optical disc is an electronic data storage medium that can be written

to and read using a low-powered laser beam. Originally developed in the late

1960s, the first optical disc, created by James T. Russell,

stored data as micron-wide dots of light and dark.

A laser read the dots, and the data was converted to

an electrical signal, and finally to audio or visual

output. However, the technology didn't appear in

the marketplace until Philips and Sony came out with the compact

disc (CD) in 1982. Since then, there has been a constant succession of optical

disc formats, first in CD formats, followed by a number of DVD formats.

Optical disc offers a number of advantages over magnetic storage media.

An optical disc holds much more data. The greater control and focus possible

with laser beams (in comparison to tiny magnetic

heads) means that more data can be written into a

smaller space. Storage capacity increases with

each new generation of optical media.

Emerging standards, such as Blu-ray, offer up

to 27 gigabytes (GB) on a single-sided 12-

centimeter disc. In comparison, a diskette, for

example, can hold 1.44 megabytes (MB). Optical discs are inexpensive to

manufacture and data stored on them is relatively impervious to most

environmental threats, such as power surges, or magnetic disturbances.

CD-ROM

CD-ROM (Compact Disc, read-only-memory) is an adaptation of the

CD that is designed to store computer data in the form of text and graphics, as

well as hi-fi stereo sound. The original data format standard

was defined by Philips and Sony in the 1983 Yellow

Book. Other standards are used in conjunction

with it to define directory and file

structures, including ISO 9660, HFS

(Hierarchal File System, for Macintosh

computers), and Hybrid HFS-ISO. Format of the

CD-ROM is the same as for audio CDs: a standard CD is 120 mm

(4.75 inches) in diameter and 1.2 mm (0.05 inches) thick and is composed of a

polycarbonate plastic substrate (under layer – this is the main body of the disc),

one or more thin reflective metal (usually aluminum) layers, and a lacquer

coating.

The Yellow Book specifications were so general that there was some

fear in the industry that multiple incompatible and proprietary formats would

be created. In order to prevent such an occurrence, representatives from

industry leaders met at the High Sierra Hotel in Lake Tahoe to collaborate on a

common standard. Nicknamed the High Sierra Format, this version was later

modified to become ISO 9660. Today, CD-ROMs are standardized and will

work in any standard CD-ROM drive. CD-ROM drives can also read audio

compact discs for music, although CD players cannot read CD-ROM discs.

CD-ROM Data Storage

Although the disc media and the drives of the CD and CD-ROM are, in

principle, the same, there is a difference in the way data storage is organized.

Two new sectors were defined, Mode 1 for storing computer data and Mode 2

for compressed audio or video/graphic data.

CD-ROM Mode 1

CD-ROM Mode 1 is the mode used for CD-ROMs that carry data and

applications only. In order to access the thousands of data files that may be

present on this type of CD, precise addressing is necessary. Data is laid out in

nearly the same way as it is on audio disks: data is stored in sectors (the

smallest separately addressable block of information), which each hold 2,352

bytes of data, with an additional number of bytes used for error detection and

correction, as well as control structures. For mode 1 CD-ROM data storage, the

sectors are further broken down, and 2,048 used for the expected data, while

the other 304 bytes are devoted to extra error detection and correction code,

because CD-ROMs are not as fault tolerant as audio CDs. There are 75 sectors

per second on the disk, which yields a disc capacity of 681,984,000 bytes

(650MB) and a single speed transfer rate of 150 kbps, with higher rates for

faster CD-ROM drives. Drive speed is expressed as multiples of the single

speed transfer rate, as 2X, 4X, 6X, and so on. Most drives support CD-ROM

XA (Extended Architecture) and Photo-CD (including multiple session discs).

CD-ROM Mode 2

CD-ROM Mode 2 is used for compressed audio/video information and uses

only two layers of error detection and correction, the same as the CD-DA.

Therefore, all 2,336 bytes of data behind the sync and header bytes are for user

data. Although the sectors of CD-DA, CD-ROM Mode 1 and Mode 2 are the

same size, the amount of data that can be stored varies considerably because of

the use of sync and header bytes, error correction and detection. The Mode 2

format offers a flexible method for storing graphics and video. It allows

different kinds of data to be mixed together, and became the basis for CD-

ROM XA. Mode 2 can be read by normal CD-ROM drives, in conjunction with

the appropriate drivers.

Data Encoding and Reading

The CD-ROM, like other CD adaptations, has data encoded in a spiral track

beginning at the center and ending at the outermost edge of the disc. The spiral

track holds approximately 650 MB of data. That's about 5.5 billion bits. The

distance between two rows of pits, measured from the center of one track to the

center of the next track is referred to as track pitch. The track pitch can range

from 1.5 to 1.7 microns, but in most cases is 1.6 microns.

Constant Linear Velocity (CLV) is the principle by which data is read from a

CDROM. This principal states that the read head must interact with the data

track at a constant rate, whether it is accessing data from the inner or outermost

portions of the disc. This is affected by varying the rotation speed of the disc,

from 500 rpm at the center, to 200 rpm at the outside. In a music CD, data is

read sequentially, so rotation speed is not an issue. The CD-ROM, on the other

hand, must read in random patterns, which necessitates constantly shifting

rotation speeds. Pauses in the read function are audible, and some of the faster

drives can be quite noisy because of it.

Magnetic Tape

The use of magnetic media to record and store numeric and textual

information, sound, motion, and still images has presented librarians and

archivists with opportunities and challenges. On the one hand, magnetic media

increase the kinds of artifacts and events we can capture and store. On the other

hand, their special long-term storage needs are different from traditional library

materials, confusing to those in charge of their care, and demanding of

resources not always available to libraries and archives. Audio and video

collections require specific care and handling to ensure that the recorded

information will be preserved. Special storage environments may be required if

the recorded information is to be preserved for longer than ten years. For

information that must be preserved indefinitely, periodic transcription from old

media to new media will be necessary, not only because the media are unstable,

but because the recording technology will become obsolete. As an information

storage medium, magnetic tape is not as stable as film or paper. Properly cared

for, film and nonacid paper can last for centuries, whereas magnetic tape will

only last a few decades. Use of magnetic media for storage is further

confounded by the prevalence of several formats (e.g., U-mastic, VHS, S-VHS,

8mm, and Beta Cam for video), media types (iron oxide, chromium dioxide,

barium ferrite, metal particulate, and metal evaporated), and by rapid advances

in media technology. On the other hand, books have virtually maintained the

same format for centuries, have almost exclusively used ink on paper as the

information storage medium, and require no special technology to access the

recorded information. Likewise, newer microfilm, microfiche, and movie film

are known for their stability when kept in proper environments, and viewing

formats have not changed significantly over the years. (The breakdown of

acetate backing that plagues older film materials is discussed in Section 2.3:

Substrate Deformation.) This report will compare care and handling procedures

for tapes with procedures for paper and film whenever possible.

Zip Drives

A Zip drive is a small, portable disk drive used primarily for backing up and

archiving personal computer files. The trademarked Zip drive was developed

and is sold by Iomega Corporation. Zip drives and disks come in two sizes. The

100 megabyte size actually holds 100,431,872 bytes of data or the equivalent of

70 floppy diskettes. There is also a 250 megabyte drive and disk. The Iomega

Zip drive comes with a software utility that lets you copy the entire contents of

your hard drive to one or more Zip disks.

In addition to data backup, Iomega suggests these additional uses:

• Archiving old e-mail or other files you don't use any more but may want

to access someday

• Storing unusually large files, such as graphic images that you need

infrequently

• Exchanging large files with someone

• Putting your system on another computer, perhaps a portable computer

• Keeping certain files separate from files on your hard disk (for example,

personal finance files)

The Zip drive can be purchased in either a parallel or a Small Computer System

Interface (SCSI) version. In the parallel version, a printer can be chained off

the Zip drive so that both can be plugged into your computer's parallel port.

DVD

DVD (digital versatile disc) is an optical disc technology that is expected to

rapidly replace the CD-ROM disc (as well as the audio compact disc) over the

next few years. The digital versatile disc (DVD) holds 4.7 gigabyte of

information on one of its two sides, or enough for a 133-minute movie. With

two layers on each of its two sides, it will hold up to 17 gigabytes of video,

audio, or other information. (Compare this to the current CD-ROM disc of the

same physical size, holding 600 megabyte. The DVD can hold more than 28

times as much information!) DVD-Video is the usual name for the DVD format

designed for full-length movies and is a box that will work with your television

set. DVD-ROM is the name of the player that will (sooner or later) replace

your computer's CD-ROM. It will play regular CDROM discs as well as DVD-

ROM discs. DVD-RAM is the writeable version. DVD Audio is a player

designed to replace your compact disc player. DVD uses the MPEG-2 file and

compression standard. MPEG-2 images have four times the resolution of

MPEG-1 images and can be delivered at 60 interlaced fields per second where

two fields constitute one image frame. (MPEG-1 can deliver 30 nonintegrated

frames per second.) Audio quality on DVD is comparable to that of current

audio compact discs.

NETWORKNETWORKNETWORKNETWORKSSSS

Introduction

After learning the section you will be able to describe Communication,

Data Communications, Data Transmission, Networks, and different Hardware

and software used to communicate between computers effectively.

Computer Network and Usage

A network is a collection of computers and devices connected by

communications channels that facilitates communications among users and

allows users to share resources with other users. Some examples of resources

are data, information, hard ware, and software. The following paragraphs

explain the advantages of using a network.

Facilitating Communications

Using a network, people can communicate efficiently and easily via e-

mail, instant messaging, chat rooms, telephony, video telephone calls, and

videoconferencing. Sometimes these communications occur within a business’s

network. Other times, they occur globally through the Internet. As discussed

earlier in this chapter, users have a multitude of devices available to send and

receive communications.

Sharing Hardware

In a networked environment, each computer on a network can access

and use hardware on the network. Suppose several personal computers on a

network each require the use of a laser printer. If the personal computers and a

laser printer are connected to a network, the personal computer users each can

access the laser printer on the network, as they need it. Business and home

users network their hardware for one main reason. That is, it may be too costly

to provide each user with the same piece of hardware such as a printer.

Sharing Data and Information

In a networked environment, any authorized computer user can access

data and information stored on other computers on the network. A large

company, for example, might have a database of customer information. Any

authorized per son, including a mobile user using a handheld computer to

connect to the network, can access this database. The capability of providing

access to and storage of data and information on shared storage devices is an

important feature of many networks.

Sharing Software

Users connected to a network can access software (programs) on the

network. To support multiple user access of software, most software vendors

sell network versions of their software. In this case, software vendors issue a

site license. A site license is a legal agreement that allows multiple users to run

the software package simultaneously. The site license fee usually is based on

the number of users or the number of computers attached to the network.

Sharing software via a network usually costs less than buying individual copies

of the software package for each computer.

Many mobile users today access their company networks through a

virtual private network. When a mobile user connects to a main office using the

Internet, a virtual private network (VPN) provides the mobile user with a

secure connection to the company network server, as if the user had a private

line. VPNs help to ensure that transmitted data is safe from being intercepted

by unauthorized people.

Problems Associated with Standalone Computers

� Sharing Hardware devices such as printers, scanners and Hard Disks.

� Difficulties in sharing software.

� Difficulties in sharing data and Information.

� Storage problems.

� Difficulties of communication between computers.

Introduction

Computers were stand-alone devices when first introduced. As they

became more widely used, manufacturers designed hardware and software so

one computer could communicate with another. Computer communications

describes a process in which one computer transfers data, instructions, and

information to another computer(s). Originally, only large computers had

communications capabilities. Today, even the smallest computers and devices

can communicate with one another. The Internet provides a means for

worldwide communications.

What is a Communication?

The following picture shows a sample communications system. As

illustrated in this figure, communications systems contain all types of devices.

An example of a communications system. Some devices that can serve

as sending and receiving devices are

a) Personal computers

b) Notebook computers

c) Web enabled cellular telephones

d) Web-enabled handheld computers

e) MSN TV

f) GPS receivers

The communications channel consists of telephone lines, underground

cables, microwave stations, and satellites. The primary function of a

communications device, such as a modem, is to convert or format signals so

they are suitable for the communications channel or a receiving device. When

using a telephone line as the communications channel, you need a modem to

convert between analog and digital signals. An analog signal consists of a

continuous electrical wave. Computers, however, process data as digital

signals. A digital signal consists of individual electrical pulses that represent

the bits grouped together into bytes.

For instance, a modem connected to a sending computer converts the

computer’s digital signals into analog signals. The analog signals then travel

over a communications channel, such as a standard telephone line. At the

receiving end, another modem converts the analog signals back into digital

signals that a receiving computer can recognize.

Sending and Receiving Devices

Sending and receiving devices initiate or accept transmission of data,

instructions, and information. Notebook computers, desktop computers, mid-

range servers, and main frame computers all can serve as sending and receiving

devices. These computers can communicate directly with another computer,

with hundreds of computers on a company network, or with millions of other

computers on the Internet.

A modem converts the individual electrical pulses of a digital signal into

analog signals for data transmission over some telephone lines. At the receiving

computer, another modem converts the analog signals back into digital signals

that the computer can process.

Basic Requirements for Successful Communications

For successful communications, you need the following:

� A sending device that initiates an instruction to transmit data,

instructions, or information.

� A communications device that converts or formats the data, instructions,

or information from the sending device into signals carried by a

communications channel.

� A communications channel, or path, on which the signals travel.

� A communications device that receives the signals from the

communications channel and converts or formats them so the receiving

device can recognize the signals.

� A receiving device that accepts the transmission of data, instructions, or

information.

Communication Types

Simplex Communication

Simplex data communication specifies that communication on a given

channel can only flow in one direction. In this environment, only one entity is

allowed to transmit and all others act as receivers. It should be noted that the

sending device cannot receive data and the receiving entity cannot transmit

data. Perhaps a good analogy of this type of communication would be your

local radio station. The radio station broadcasts a message (the transmitting

device) and you receive the message on your radio (the receiving device). This

represents a one-way communication stream. Simplex Communication Data

transfer in one direction only.

Half-Duplex Communication

Unlike simplex communication, half-duplex communication allows each

device to send and receive data, but only one device at a time can transmit. A

key point is that when you are transmitting the entire channel is being used for

that purpose. You cannot receive and transmit at the same time. The best

example of this would be a child’s walkie-talkie. You push a button to talk and

release it to receive. It can best be stated by saying half- duplex provides for bi-

directional communication, but only in one direction at a time.

Half-Duplex Communication Data transfer both directions but only one

direction at a time.

Full-Duplex Communication

Full-duplex communication provides for two-way communicate at the

same time. An everyday example of full-duplex communication would be your

basic telephone system. Unlike the walkie-talkies (half duplex), full-duplex

communication allows both parties to transmit and receive at the same time.

Full-Duplex Communication Data transfer both directions at the same

time.

Data Communication

Analog Signal

In telecommunications, an analog signal is one in which a base carrier's

alternating current frequency is modified in some way, such as by amplifying

the strength of the signal or varying the frequency, in order to add information

to the signal. Broadcast and telephone transmission have conventionally used

analog technology.

An analog signal can be represented as a series of sine waves. The term

originated because the modulation of the carrier wave is analogous to the

fluctuations of the human voice or other sound that is being transmitted.

Analog describes any fluctuating, evolving, or continually changing

process.

Digital Signal

Digital describes electronic technology that generates, stores, and

processes data in terms of two states: positive and non-positive. Positive is

expressed or represented by the number 1 and non-positive by the number 0.

Thus, data transmitted or stored with digital technology is expressed as a string

of 0's and 1's. Each of these state digits is referred to as a bit (and a string of

bits that a computer can address individually as a group is a byte).

Prior to digital technology, electronic transmission was limited to analog

technology, which conveys data as electronic signals of varying frequency or

amplitude that are added to carrier waves of a given frequency. Broadcast and

phone transmission has conventionally used analog technology.

Digital technology is primarily used with new physical communications

media, such as satellite and fiber optic transmission. A modem is used to

convert the digital information in your computer to analog signals for your

phone line and to convert analog phone signals to digital information for your

computer.

Types of Transmission Media

Transmission Media, Network Cables and Connectors

Perhaps the most important network components are the media and

connectors used to attach computers to the system. The word “media” simply

refers to the physical pathway on which network data travels. In most cases,

this media is some type of cable. We refer to these cables as bounded media.

Within the networking environment, many different types of bounded media

are used. Each of these has very different characteristics such as speed,

maximum length and connection types. The following is a list of the most

common type of cables:

Cable media

Coaxial cable, Unshielded twisted pair cable, Shielded twisted pair

cable, Fiber optic cable.

Wireless media

Radio Frequency, Infrared, Microwave.

Twisted Pair

Twisted pair cable consists of at least two insulated wires twisted

together to reduce the effects of crosstalk. There are two broad categories of

twisted pair cables. They are UTP (unshielded twisted pair cable) and STP

(shielded twisted pair cable).

STP (Shielded Twisted Pair) cable is very resistant to environmental

factors like EMI because of the added layer of shielding that surrounds the

twisted wires. STP cable tends to be more expensive than UTP and is also

harder to work with than the thinner unshielded variety. The most common

implementation of STP is for IBM Token ring cables.

UTP (Shielded Twisted Pair), as the name would imply, does not have

an added layer of shielding and is therefore thinner and cheaper to

manufacture. UTP cable is rated in categories: Category 3 and 5 are the most

common for data grade transmissions. The CAT 3 cable was dominant in the

early years of networking but has been replaced by CAT 5 wiring because.

CAT 5 is better able to create a stable platform for data transmissions greater

than 10 Mbps. The CAT 5 twisted pair cable can support speeds of 100 Mbps.

The main physical difference between CAT 3 and CAT 5 cable is the number

of twists per inch. The CAT 5 cable has many more twists than CAT 3,

eliminating most crosstalk. UTP cable closely resembles the cable used by

telephones in your home.

Coaxial Cable

Coaxial cable, typically called coax cable, uses a center core conductor

that is insulated and surrounded by either a braided or solid thin foil aluminum

shield. Coax cable is very similar in appearance to the type used by television

cable companies in your home.

However, it should be noted that these are not the same and can not be

interchanged. Due to the amount of shielding, coax cable is very resistant to

crosstalk (interference from adjacent wires) and EMI (electromagnetic

interference). The graphic below shows that a coax cable is composed of an

outer jacket, an outer shield, an insulator and the center conductor.

Fiber Optic

Fiber optic cable uses a small strand of glass or plastic, instead of

copper, as the core of the cable. It consists of a glass center core surrounded by

a plastic sheath and a layer of gel or wire stands. Fiber optic cable offers a

major advantage over copper wire. It is almost completely immune to EMI and

does not suffer from attenuation (loss of signal strength over distance) like

copper cable. Fiber cable tends to be very expensive as compared to copper

wire. However, this cost variance should decrease as more companies choose

to implement this technology.

Advantages over copper-based media:

� Supports greater distances (up to 4 kilometers)

� Immune to EMI (Electromagnetic Interference)

� Immune to RFI (Radio Frequency Interference)

� Disadvantages of Fiber-Optic Cable:

� More expensive than copper-based media

� Difficult to install and support.

Wireless Media

After discussing coaxial, twisted pair and fiber optic cable, one might

get the impression that these are the only media options available. Copper and

fiber optic cabling are by far the most prevalent implementations. However,

there is another option that is gaining more acceptances in the networking

world. This option is wireless media. Wireless technology is not new. In fact,

the technology has been around for many years. This technology allows

computers fitted with special wireless adapters (NICs) to communicate with

other network devices, computers, printers, etc. without the use of cables.

To date, wireless networks have been limited mostly to smaller

workgroup environments supporting only a limited number of computers and

peripheral devices. These wireless networks can also become part of a larger

cabled network using special wireless ports called access points. The access

point is actually a device that converts the wireless signal to a signal that can be

placed on a cabled network. These devices can be dedicated access points or

simply a computer equipped with both a wireless adapter and a conventional

NIC, which is connected to the larger network via copper or fiber optic cable.

There are basically two different types of technology used in wireless

communications, RF (Radio Frequencies) and infrared technology. Of the two,

infrared technology is the one most often implemented in workgroup

environments. Whether using RF or infrared technologies, environmental

conditions and distance factors will have a significant influence on the

performance expectations of the network. The typical wireless access point can

normally support up to about twenty computers within a 30 to 60 meter radius.

This is would be under ideal conditions. Other factors, such as

intervening walls and environmental conditions, may reduce performance and

distance even further.

Radio frequency

Radio frequency (abbreviated RF, rf, or r.f.) is a term that refers to

alternating current (AC) having characteristics such that, if the current is input

to an antenna, an electromagnetic (EM) field is generated suitable for wireless

broadcasting and/or communications. These frequencies cover a significant

portion of the electromagnetic radiation spectrum, extending from nine

kilohertz (9 kHz), the lowest allocated wireless communications frequency (it's

within the range of human hearing), to thousands of gigahertz (GHz).

Transmission of Digital Data

A modem modulates outgoing digital signals from a computer or other

digital device to analog signals for a conventional copper twisted pair

telephone line and demodulates the incoming analog signal and converts it to a

digital signal for the digital device.

In recent years, the 2400 bits per second modem that could carry e-mail

has become obsolete. 14.4 Kbps and 28.8 Kbps modems were temporary

landing places on the way to the much higher bandwidth devices and carriers of

tomorrow. From early 1998, most new personal computers came with 56 Kbps

modems. By comparison, using a digital Integrated Services Digital Network

adapter instead of a conventional modem, the same telephone wire can now

carry up to 128 Kbps. With Digital Subscriber Line (DSL) systems, now being

deployed in a number of communities, bandwidth on twisted-pair can be in the

megabit range.

Information Networks

LAN

A local area network (LAN) is a group of computers and associated

devices that share a common communications line or wireless link and

typically share the resources of a single processor or server within a small

geographic area (for example, within an office building). Usually, the server

has applications and data storage that are shared in common by multiple

computer users. A local area network may serve as few as two or three users

(for example, in a home network) or as many as thousands of users (for

example, in an FDDI network).

MAN

A metropolitan area network (MAN) is a network that interconnects

users with computer resources in a geographic area or region larger than that

covered by even a large local area network (LAN) but smaller than the area

covered by a wide area network (WAN).

The term is applied to the interconnection of networks in a city into a

single larger network (which may then also offer efficient connection to a wide

area network). It is also used to mean the interconnection of several local area

networks by bridging them with backbone lines. The latter usage is also

sometimes referred to as a campus network.

Examples of metropolitan area networks of various sizes can be found in

the metropolitan areas of London, England; Lodz, Poland; and Geneva,

Switzerland. Large universities also sometimes use the term to describe their

networks. A recent trend is the installation of wireless MANs.

WAN

A wide area network (WAN) is a geographically dispersed

telecommunications network. The term distinguishes a broader

telecommunication structure from a local area network. A wide area network

may be privately owned or rented, but the term usually connotes the inclusion

of public (shared user) networks. An intermediate form of network in terms of

geography is a metropolitan area network (MAN).

Network Topology

Network topology refers to how your network is wired (the physical

configuration). Choosing the right configuration (topology) for a given

situation can directly affect a network’s speed, its flexibility to expand and just

how robust or fault- tolerant it is. There are many choices for designing a

network topology. The most common choices are:

1. Bus

2. Star

3. Ring

4. Mesh

5. Hybrid

It should be noted that there are many variations and hybrids of the

above topologies. These topologies can exist separately or in a mixed

environment. It should be stressed that a mixture of topologies is much harder

to administrate and more difficult to troubleshoot.

Bus

The basic bus topology is relatively easy to install and requires the least

amount of media (cable) as compared to the other topologies. Every computer

or device is connected to the next in a daisy-chain fashion. The first and last

device on the chain must be terminated with a resistor that matches the

impedance of cable that you are using. While the bus topology is fairly easy to

install, it can be one of the most difficult to troubleshoot. Another major

limitation of a bus topology is that a cable fault or break anywhere down the

length of the cable will affect all computers on that segment. The graphic

below depicts an example of a bus topology. One very common

implementation of the bus topology is Apple’s Local Talk, which is a

proprietary Data Link layer implementation developed by Apple Computer for

its AppleTalk protocol suite. Local Talk was designed as a cost-effective

network solution for connecting local workgroups. Local Talk hardware

typically is built into Apple products, which are easily connected by using

inexpensive twisted-pair cabling. Local Talk networks are almost always

organized in a bus topology.

A Diagram of a Bus Topology

Star

The most important distinction between the bus topology and the star

topology is that a star topology offers a much higher degree of redundancy.

Unlike the bus topology where one fault could bring Dow n the entire network,

the star connects each computer with its own dedicated cable. A failure of one

cable will affect only that machine. A star topology also tends to be much more

flexible if you have to move or reconfigure computers. The cost of this

topology is somewhat higher with the added expense of using a hub or

concentrator. However this cost is more than justified if you ever have the need

to troubleshoot the cable plant. The example below depicts a star topology.

A Diagram of a Star Topology

Ring

A ring topology is made up of computers that are connected in a circular

configuration. Each computer or device in the ring is connected to two others.

Data in this configuration travels around the ring in one direction and each

device in the ring can also act as repeater to boost the signal if necessary. A

ring topology generally uses more cable than either the bus or the star. A ring

topology is shown below.

A Diagram of a Ring Topology

Hybrid

A combination of any two or more network topologies. Note 1:

Instances can occur where two basic network topologies, when connected

together, can still retain the basic network character, and therefore not be a

hybrid network. For example, a tree network connected to a tree network is still

a tree network. Therefore, a hybrid network accrues only when two basic

networks are connected and the resulting network topology fails to meet one of

the basic topology definitions. For example, two star networks connected

together exhibit hybrid network topologies. Note 2: A hybrid topology always

accrues when two different basic network topologies are connected.

A Diagram of a Hybrid Topology

Mesh

The mesh topology is by far the most redundant of all of the topologies

mention so far. However, this does come with an added expense. The mesh

topology requires much more cable than any of the other topologies. In a true

mesh topology, every device is directly connected to every other device. It is

this configuration that makes it so redundant. However, if there ever is a

problem, it can be very difficult to locate the offending cable. The example

below depicts a mesh topology.

A Diagram of a Mesh Topology

Network Operating Systems

A Network Operating System (NOS) is a specific kind of program

designed to allow users to share resources over a computer network. These

resources may include other programs and files as well as printers and other

hardware. The Network Operating System sets the rules for this sharing of

resources and allows a variety of kinds of computers and components to

communicate. The most significant Network Operating Systems today are

Microsoft’s Windows NT and Windows 2000, Novell NetWare and the

different versions of UNIX and Linux.

Client/Server Networking

One concept that is important in our discussion of Operating Systems is

the concept of client/server networking. In this section, we will focus on the

server side of networking. In an o future section we will turn our focus to the

client side.

Servers

In a client/server networking environment, certain systems are set up as

servers, which means that they serve resources to other systems. Servers can

provide various functions. For example, a server might be set up as a print

server in order to manage the printing on a network. Or a server might play the

role of a file server, hosting files on a network so that users can share and

access files were the network. Servers may also act as application servers to

host applications that are used on the network. Another important role that is

frequently performed by servers is to control security on the network to ensure

that only authorized users are able to access network resources. It is important

to note that typically servers are the bigger, faster machines on the network and

are often dedicated servers that perform very specific functions. There are

instances, however, when a server may act as both a server and a client.

Clients

Very simply, clients are the systems on the network that request and

access information from the servers. These are the systems that end users sit at

to perform their work. Another term that is used almost interchangeably with

client is workstation.

OSI Model

In response to the need for networking standards, various industry

organizations attempted to create models. Most of these models dealt with the

issues of moving information or data from one location to another. The work of

these various industry organizations laid the groundwork for what was to

become the most widely accepted model for networking, the OSI (Open

Systems Interconnection) model. In about 1977, the ISO (International

Organization for Standards) adopted a mandate to develop a set of standards

that would address the issues of interoperability in a multivendor environment.

The fruits of their labor became the OSI model.

The OSI model subdivides the intricacies of networking into seven

separate parts:

1. Application

2. Presentation

3. Session

4. Transport

5. Network

6. Data link

7. Physical

It is important to keep in mind that the OSI model is a design or

blueprint for how communication should occur. It attempts to divide the

otherwise complicated task of communication between devices into logical sub

groups called layers. This process is somewhat akin to the task of building a

house. Viewing this process as a whole can be quite overwhelming. However,

most houses are built by subcontractors, each specializing in a particular area.

This is exactly what the OSI model does for networking, creating individual

layers at which software and hardware vendors can function. This means, for

example, that a manufacturer of network interface cards needs only to be

familiar with standards set by the lower layers of the OSI model, while a

software vendor of a terminal emulation program might be concerned only with

the upper few layers of the model.

What is a Protocol?

When data is being transmitted between two or more devices something

needs to govern the controls that keep this data intact. A formal description of

message formats and the rules two computers must follow to exchange those

messages. Protocols can describe low-level details of machine-to-machine

interfaces (e.g., the order in which hits and bytes are sent across wire) or high-

level exchanges between application programs (e.g., the way in which two

programs transfer a file across the Internet)

TCP/IP

TCP

The main function of TCP is to establish and monitor connections

between the sending and receiving devices. TCP is responsible for providing

reliable connection-oriented data delivery. TCP functions at the Transport layer

of the OSI model. When you are using TCP, you basically have an

acknowledgement between sender and receiver that is maintained the entire

length of the data transmission.

IP

Internet Protocol provides the mechanism for Internet addressing. IP

functions at the Network layer of the OSI model. There are basically two parts

to an IP address; the first part defines the network a device is attached to, and

the second portion identifies the actual device itself. An IP address can be

assigned by the network administrator or assigned by a DHCP (Dynamic Host

Configuration Protocol) server.

NetBEUI

NetBEUI (NetBIOS Extended User Interface) is a new, extended

version of NetBIOS, the program that lets computers communicates within a

local area network. NetBEUI (pronounced net-BOO-ee) formalizes the frame

format (or arrangement of information in a data transmission) that was not

specified as part of NetBIOS. NetBEUI was developed by IBM for its LAN

Manager product and has been adopted by Microsoft for its Windows NT,

LAN Manager, and Windows for Workgroups products. Hewlett-Packard and

DEC use it in comparable products. NetBEUI is the best performance choice

for communication within a single LAN. Because, like NetBIOS, it does not

support the routing of messages to other networks, its interface must be adapted

to other protocols such as Internet work Packet Exchange or TCP/IP. A

recommended method is to install both NetBEUI and TCP/IP in each computer

and set the server up to use NetBEUI for communication within the LAN and

TCP/IP for communication beyond the LAN.

IPX/SPX

IPX (Internet work Packet Exchange) is a networking protocol from

Novell that interconnects networks that use Novell's NetWare clients and

servers. IPX is a datagram or packet protocol. IPX works at the Network layer

of communication protocols and is connectionless (that is, it doesn't require that

a connection be maintained during an exchange of packets as, for example, a

regular voice phone call does).

Packet acknowledgment is managed by another Novell protocol, the

Sequenced Packet Exchange (SPX). Other related Novell NetWare protocols

are: the Routing Information Protocol (RIP), the Service Advertising Protocol

(SAP), and the NetWare Link Services Protocol (NLSP).

CHARACTERISTICS OF AN IPX/SPX NUMBER

A datagram passed in an IPX internet work contains the following information:

1. A 30-byte IPX header (includes network, node, and socket number of

both source and destination addresses)

2. Data section: includes SPX header (or some other type, but often SPX)

Since IPX is connectionless, the minimum packet size is only 30-bytes

(excluding MAC header). Since SPX provides reliable connections (but is not

mandatory) it may not be included. IPX has a maximum packet size of 65,535

bytes (includes data obviously). The MAC header comes before the IPX header

and the data. Now, the IPX network number is 4-bytes, hexadecimal. This is

the basis for packet routing. Each destination in internet work has their own

number. The network number may contain up to eight digits, wile leading

zeroes are often not displayed. Novell Server can automatically detect network

numbers on the internet work. Routers send a RIP request packet to determine

network numbers and frame types to use. The Node number is 6 bytes,

hexadecimal. This number uniquely identifies a device on the internet work and

is akin to the interface connected to that device. This number need only be

unique in the IPX network to which it is a member.

HTTP

HTTP (Hypertext Transfer Protocol) is in widespread use today. HTTP

is used to transfer Web pages from a Web server to a local Web browser. Those

Web pages are created as HTML (Hypertext Markup Language) documents.

HTTP also has a sister protocol called HTTP(S), which allows for secure

transfer of documents. While HTTPS is slower due to the overhead generated

by encryption methods, most would agree that it is essential for e-commerce

and on-line banking transactions.

FTP

FTP (File Transfer Protocol) is somewhat unique in that it is both a

protocol and a program. It is usually associated most closely with the UNIX

environment. As the name would indicate, it is used to transfer files. It is very

powerful and flexible in its use. It can be configured to let users take files but

not transmit them. This could be very advantageous in the case of limiting the

transfer of files that may contain a virus.

There is also a stripped down version of FTP called TFTP (Trivial File

Transfer Protocol) which lacks some of the functionality of FTP in particular

the ability to browse for files. Most FTP access is granted using the

“anonymous” user account. FTP can be very useful when troubleshooting or

servicing an IP-based network. It can be used to download fixes, patches and

standard ASCII read me files. The FTP utility is actually a collection of

separate FTP commands. The list below displays some of the most popular

commands along with their use.

� Help Displays Help screen for commands

� CD Changes the directory on a remote disk

� LCD Changes the directory on a local disk

� DIR Displays a descriptive list of files on remote computers

� BINARY Transfers a binary file format

� ASCII Transfers an ASCII file format

� PUT Transmits files to remote computers

� GET Retrieves files from remote computers

� QUIT/BYE Ends and exits an FTP session

SMTP

SMTP (Simple Mail Transfer Protocol) provides a mechanism to send

email between dissimilar operating systems. It is SMTP’s ability to send email

between different operating systems that makes it so useful on the Internet. An

example of this would be composing an email message from a Windows 98

client, forwarding that to a local Microsoft Exchange Server which could then

send it via the Internet to a server running the UNIX operating system.

NNTP

NNTP (Network News Transfer Protocol) is the predominant protocol

used by computer clients and servers for managing the notes posted on Usenet

newsgroups. NNTP replaced the original Usenet protocol, UNIX-to-UNIX

Copy Protocol (UUCP) some time ago. NNTP servers manage the global

network of collected Usenet newsgroups and include the server at your Internet

access provider. An NNTP client is included as part of a Netscape, Internet

Explorer, Opera, or other Web browser or you may use a separate client

program called a newsreader.

P0P3

The POP3 (Post Office Protocol) version 3 is used to download email

from various servers to an email client. Microsoft’s Outlook Express is an

example of client-side software that uses POP3 technology. Most ISPs (Internet

Service Providers) that provide home service also use the POP3 protocol. This

enables the ISP to download messages to the individual user’s computer rather

than having to store them on the ISP’s servers.

Network Components

Network Interface Card

The NIC is perhaps the most common component in the network. At

least one NIC must be installed in every system attached to the network. The

NIC is an expansion board that allows the workstation or server to attach to a

common cabling system. Most network interface cards provide for more than

just one cable type. The most common connection types are twisted pair

(RJ45), coax (BNC) connectors and fiber optic connections.

Cables and Connectors

Coaxial Cable

Coaxial cable is the kind of copper cable used by cable TV companies

between the community antenna and user homes and businesses. Coaxial cable

is sometimes used by telephone companies from their central office to the

telephone poles near users. It is also widely installed for use in business and

corporation Ethernet and other types of local area network. Coaxial cable is

called “coaxial” because it includes one physical channel that carries the signal

surrounded (after a layer of insulation) by another concentric physical channel,

both running along the same axis. The outer channel serves as a ground. Many

of these cables or pairs of coaxial tubes can be placed in a single outer

sheathing and, with repeaters, can carry information for a great distance.

Coaxial cable was invented in 1929 and first used commercially in 1941.

AT&T established its first cross-continental coaxial transmission system in

1940. Depending on the carrier technology used and other factors, twisted pair

copper wire and optical fiber are alternatives to coaxial cable.

BNC Connector used with Coaxial Cable

A BNC (Bayonet Neil-Concelman, or sometimes British Naval

Connector) connector is used to connect a computer to a coaxial cable in a

10BASE-2 Ethernet network.

10BASE-2 is a 10 MHz base band network on a cable extending up to

185 meters - the 2 is a rounding up to 200 meters - without a repeater cable.

10BASE-2 Ethernets are also known as “Thin net”, “thin Ethernet”, or

“cheaper nets”. The wiring in this type of Ethernet is thin, 50 ohm, base band

coaxial cable. The BNC connector in particular is generally easier to install and

less expensive than other coaxial connectors.

A BNC male connector has a pin that connects to the primary

conducting wire and then is locked in place with an outer ring that turns into

locked position. Different sources offer different meanings for the letters BNC.

However, our most knowledgeable source indicates that the B stands for a

bayonet-type connection (as in the way a bayonet attaches to a rifle) and the

NC for the inventors of the connector, Neil and Concelman.

Twisted Pair

Twisted pair is the ordinary copper wire that connects home and many

business computers to the telephone company. To reduce crosstalk or

electromagnetic induction between pairs of wires, two insulated copper wires

are twisted around each other. Each connection on twisted pair requires both

wires. Since some telephone sets or desktop locations require multiple

connections, twisted pair is sometimes installed in two or more pairs, all within

a single cable. For some business locations, twisted pair is enclosed in a shield

that functions as a ground. This is known as shielded twisted pair (STP).

Ordinary wire to the home is unshielded twisted pair (UTP). Twisted pair is

now frequently installed with two pairs to the home, with the extra pair making

it possible for you to add another line (perhaps for modem use) when you need

it. Twisted pair comes with each pair uniquely color coded when it is packaged

in multiple pairs. Different uses such as analog, digital, and Ethernet require

different pair multiples. Although twisted pair is often associated with home

use, a higher grade of twisted pair is often used for horizontal wiring in LAN

installations because it is less expensive than coaxial cable. The wire you buy

at a local hardware store for extensions from your phone or computer modem

to a wall jack is not twisted pair. It is a side-by-side wire known as silver satin.

The wall jack can have as many five kinds of hole arrangements or pin outs,

depending on the kinds of wire the installation expects will be plugged in (for

example, digital, analog, or LAN) . (That’s why you may sometimes find when

you carry your notebook RJ45 Connectors are used with Twisted pair cables.

In the U. S., telephone jacks are also known as registered jacks,

sometimes described as RJ-XX, and are a series of telephone connection

interfaces (receptacle and plug) that are registered with the U.S. Federal

Communications Commission (FCC). They derive from interfaces that were

part of AT&T’s Universal Service Order Codes (USOC) and were adopted as

part of FCC regulations (specifically Part 68, Subpart F. Section 68.502). The

term jack sometimes means both receptacle and plug and sometimes just the

receptacle.

RJ-45

The RJ-45 is a single-line jack for digital transmission over ordinary

phone wire, either untwisted or twisted. The interface has eight pins or

positions. For connecting a modem, printer, or a data PBX at a data rate up to

19.2 Kbps, you can use untwisted wire. For faster transmissions in which

you’re connecting to an Ethernet 10BASET network, you need to use twisted

pair wire. (Untwisted is usually a flat wire like common household phone

extension wire. Twisted is often round.) There are two varieties of RJ-45:

keyed and unkeyed. Keyed has a small bump on its end and the female

complements it. Both jack and plug must match.

Fiber Optic Cable

Fiber optic (or “optical fiber”) refers to the medium and the technology

associated with the transmission of information as light impulses along a glass

or plastic wire or fiber. Fiber optic wire carries much more information than

conventional copper wire and is far less subject to electromagnetic interference.

Most telephone company long-distance lines are now fiber optic. Transmission

on fiber optic wire requires repeating at distance intervals. The glass fiber

requires more protection within an outer cable than copper. For these reasons

and because the installation of any new wiring is labor-intensive, few

communities yet have fiber optic wires or cables from the phone company’s

branch office to local customers (known as local loop).

A Fiber Optic Cable Different kinds of Fiber Optic Connectors

Hubs and Switches

Hub

In general, a hub is the central part of a wheel where the spokes come

together. The term is familiar to frequent fliers who travel through airport

“hubs” to make connecting flights from one point to another. In data

communications, a hub is a place of convergence where data arrives from one

or more directions and is forwarded out in one or more other directions. A hub

usually includes a switch of some kind. (And a product that is called a “switch”

could usually be considered a hub as well.) The distinction seems to be that the

hub is the place where data comes together and the switch is what determines

how and where data is forwarded from the place where data comes together.

Regarded in its switching aspects, a hub can also include a router.

1. In describing network topologies, a hub topology consists of a backbone

(main circuit) to which a number of outgoing lines can be attached

(“dropped”), each providing one or more connection port for device to

attach to. For Internet users not connected to a local area network, this is

the general topology used by your access provider. Other common

network topologies are the bus network and the ring network. (Either of

these could possibly feed into a hub network, using a bridge.)

2. As a network product, a hub may include a group of modem cards for

dial-in users, a gateway card for connections to a local area network (for

example, an Ethernet or a Token Ring), and a connection to a line.

Switch

In a telecommunications network, a switch is a device that channels

incoming data from any of multiple input ports to the specific output port that

will take the data toward its intended destination. In the traditional circuit-

switched telephone network, one or more switches are used to set up a

dedicated though temporary connection or circuit for an exchange between two

or more parties. On an Ethernet local area network (LAN), a switch determines

from the physical device (Media Access Control or MAC) address in each

incoming message frame which output port to forward it to and out of. In a

wide area packet-switched network such as the Internet, a switch determines

from the IP address in each packet which output port to use for the next part of

its trip to the intended destination. In the Open Systems Interconnection (OSI)

communications model, a switch performs the layer 2 or Data-Link layer

function. That is, it simply looks at each packet or data unit and determines

from a physical address (the “MAC address”) which device a data unit is

intended for and switches it out toward that device. However, in wide area

networks such as the Internet, the destination address requires a look-up in a

routing table by a device known as a router. Some newer switches also perform

routing functions (layer 3 or the Network layer functions in OSI) and are

sometimes called IP switches. On larger networks, the trip from one switch

point to another in the network is called a hop. The time a switch takes to

figure out where to forward a data unit is called its latency. The price paid for

having the flexibility that switches provide in a network is this latency.

Switches are found at the backbone and gateway levels of a network where one

network connects with another and at the sub network level where data is being

forwarded close to its destination or origin. The former are often known as core

switches and the latter as desktop switches. In the simplest networks, a switch

is not required for messages that are sent and received within the network. For

example, a local area network may be organized in a Token Ring or bus

arrangement in which each possible destination inspects each message and

reads any message with its address.

Repeaters

A repeater is a signal amplification device. As an electronic signal

travels down a wire it weakens in strength. In electronic jargon this is known as

attenuation. It’s much like a marathon runner getting tired and weakening as

the race progresses. Repeaters are place at predetermined points along the cable

and act to boost and retransmit the signal. This is like giving a runner a power

bar or drink at crucial points in a race.

Bridges

A bridge is a hardware device that segments a single network into two or

more logical pieces for the purpose of isolating network traffic. The operative

word here is a single network. A bridge does NOT create another new network,

because the segments still appear as one single network. Like a drawbridge that

allows or prohibits traffic from passing from one side of the bridge to the other,

a network bridge performs the same function in a network environment. The

bridge will either pass network traffic or deny network traffic based on the

destination address. If the intended address for a piece of data is located on the

“local” segment, the bridge will block the traffic from passing beyond it onto

other segments. On the other hand, if the destination address is on another

segment, the bridge will allow the traffic to pass through in order to reach its

destination. Let’s look at a simple example of why a bridge is used in a

network environment. Let’s say that, within a single network, there is a small

group of computer users that constantly exchange information and access

network resources. On this same network, there is a larger group of users that

do not use the network as much. If this network were not segmented, the first

group would actually impact the performance of the second group in a negative

way. However, if a bridge were used to segment the two groups, the first group

of more intense network users would be isolated. The bridge would identify the

traffic that belonged to the users on this local segment, and would prohibit it

from passing out onto the rest of the network. Only the traffic intended for a

computer located on the other side of the bridge will be allowed to pass. All

other network traffic would remain on the local segment.

Routers

The router is considered to be an intelligent networking device. It

performs basically two functions. First, it provides the physical connection

between two or more different networks. The second and major function is to

route packets of network information between different networks, hence the

name “router.” The router also has the intelligence built in to dynamically

adapt to changes in the network configuration and to route traffic around

downed links. By implementing a number of routers to connect several smaller

networks together, a larger entity known as an inter network is created. When a

computer located on one network wants to send data to a device located on a

remote network, the data is passed to a router located on the local segment (the

default gateway).

Brouters

The brouter is a hybrid device that, as its name would imply, combines

the functionality of both a bridge and a router into one device. It will function

as a router in most cases. However, if it cannot locate the necessary routing

information, it will perform a simple bridging function, either passing or

denying network traffic based on the MAC destination address.

Gateways

If a router is considered an intelligent networking device, the gateway

would be considered the device with a PhD. The gateway basically provides all

the functionality of a router and acts as a translator as well. The router is a

protocol- independent device, meaning it doesn’t really care what language a

computer speaks. It is just interested in getting the message from one machine

to another. The gateway performs the routing function as well as translating

between different computer languages (protocols). An example of this could be

the connection between a Windows NT/2 000 network and an IBM mainframe

environment. The word default gateway refers to a router on the network that

sends all TCP/IP packets to remote networks. The key point here is any or all

packets are sent which are not destined for the local network! Because of the

translation and other overhead involved, the gateway is the least rapid (slowest)

of the Internet work Connection Devices.

Firewalls

A firewall is a set of related programs, located at a network gateway

server that protects the resources of a private network from users from other

networks. (The term also implies the security policy that is used with the

programs.) An enterprise with an intranet that allows its workers access to the

wider Internet installs a firewall to prevent outsiders from accessing its own

private data resources and for controlling what outside resources its own users

have access to.

INTERNET & WWWINTERNET & WWWINTERNET & WWWINTERNET & WWW

Basic Concepts of Internet

The Internet

The Internet is a computer network made up of thousands of networks

worldwide. No one knows exactly how many computers are connected to the

Internet. It is certain, however, that these number in the millions.

No one is in charge of the Internet. There are organizations which

develop technical aspects of this network and set standards for creating

applications on it, but no governing body is in control. The Internet backbone,

through which Internet traffic flows, is owned by private companies.

All computers on the Internet communicate with one another using the

Transmission Control Protocol/Internet Protocol suite, abbreviated to TCP/IP.

Computers on the Internet use client/server architecture. This means that the

remote server machine provides files and services to the user’s local client

machine. Software can be installed on a client computer to take advantage of

the latest access technology.

An Internet user has access to a wide variety of services: electronic mail,

file transfer, vast information resources, interest group membership, interactive

collaboration, multimedia displays, real-time broadcasting, shopping

opportunities, breaking news, and much more.

The Internet consists primarily of a variety of access protocols. Many of

these protocols feature programs that allow users to search for and retrieve

material made available by the protocol.

Brief history

The Internet (which most people know today as the World Wide Web or

WWW) began in the United States in the 1960’s as a military project. It linked

computers and people together so that if one military base was destroyed,

information could still reach its destination simply by taking an alternative

route. This approach to linking or networking computers is still the basis of the

Internet.

Academic institutions adopted this technology to allow co-operative

work between universities, and the internet grew from there, although when the

Internet first started, people could only share text-based documents.

In 1990, the World Wide Web was developed. This made the internet

very popular, because the WWW allowed people to access information through

a graphical (picture based) interface such as the well-known browser, Netscape.

Components of the Internet

World Wide Web (WWW)

The World Wide Web (abbreviated as the Web or WWW) is a system of

Internet servers that supports hypertext to access several Internet protocols on a

single interface. Almost every protocol type available on the Internet is

accessible on the Web. This includes email, FTP, Telnet, and Usenet News. In

addition to these, the World Wide Web has its own protocol: Hypertext

Transfer Protocol, or HTTP. These protocols will be explained later in this

document.

The World Wide Web provides a single interface for accessing all these

protocols. This creates a convenient and user-friendly environment. It is no

longer necessary to be conversant in these protocols within separate, command-

level environments. The Web gathers together these protocols into a single

system. Because of this feature, and because of the Web’s ability to work with

multimedia and advanced programming languages, the Web is the fastest-

growing component of the Internet.

The operation of the Web relies primarily on hypertext as its means of

information retrieval. Hypertext is a document containing words that connect to

other documents. These words are called links and are selectable by the user. A

single hypertext document can contain links to many documents. In the context

of the Web, words or graphics may serve as links to other documents, images,

video, and sound. Links may or may not follow a logical path, as each

connection is programmed by the creator of the source document. Overall, the

Web contains a complex virtual web of connections among a vast number of

documents, graphics, videos, and sounds.

Producing hypertext for the Web is accomplished by creating documents

with a language called Hypertext Markup Language, or HTML. With HTML,

tags are placed within the text to accomplish document formatting, visual

features such as font size, italics and bold, and the creation of hypertext links.

Graphics and multimedia may also be incorporated into an HTML document.

HTML is an evolving language, with new tags being added as each upgrade of

the language is developed and released. The World Wide Web Consortium

(W3C), led by Web founder Tim Berners -Lee, coordinates the efforts of

standardizing HTML. The W3C now calls the language XHTML and considers

it to be an application of the XML language standard.

The World Wide Web consists of files, called pages or home pages,

containing links to documents and resources throughout the Internet.

E-mail

Electronic mail, or e-mail, allows computer users locally and worldwide

to exchange messages. Each user of e-mail has a mailbox address to which

messages are sent.

Messages sent through e-mail can arrive within a matter of seconds. A

powerful aspect of e-mail is the option to send electronic files to a person’s e-

mail address. Non-ASCII files, known as binary files, may be attached to e-

mail messages. These files are referred to as MIME attachments. MIME stands

for Multimedia Internet Mail Extension, and was developed to help e-mail

software handle a variety of file types. For example, a document created in

Microsoft Word can be attached to an e-mail message and retrieved by the

recipient with the appropriate e-mail program. Many email programs, including

Eudora, Netscape Messenger, and Microsoft Outlook, offer the ability to read

files written in HTML, which is itself a MIME type.

Telnet

Telnet is a program that allows you to log into computers on the Internet

and use online databases, library catalogs, chat services, and more. There are

no graphics in Telnet sessions, just text. To Telnet to a computer, you must

know its address.

This can consist of words (locis.loc.gov) or numbers (140.147.254.3).

Some services require you to connect to a specific port on the remote computer.

In this case, type the port number after the Internet address. Example: telnet

nri.reston.va.us 185. Telnet is available on the World Wide Web. Probably the

most common Web-based resources available through Telnet have been library

catalogs, though most catalogs have since migrated to the Web. A link to a

Telnet resource may look like any other link, but it will launch a Telnet session

to make the connection. A Telnet program must be installed on your local

computer and configured to your Web browser in order to work. With the

increasing popularity of the Web, Telnet has become less frequently used as a

means of access to information on the Internet.

FTP

FTP stands for File Transfer Protocol. This is both a program and the

method used to transfer files between computers. Anonymous FTP is an option

that allows users to transfer files from thousands of host computers on the

Internet to their personal computer account. FTP sites contain books, articles,

software, games, images, sounds, multimedia, course work, data sets, and

more. If your computer is directly connected to the Internet via an Ethernet

cable, you can use one of several PC software programs, such as WS_FTP for

Windows, to conduct a file transfer.

Mail Discussion Groups

One of the benefits of the Internet is the opportunity it offers to people

worldwide to communicate via e-mail. The Internet is home to a large

community of individuals who carry out active discussions organized around

topic-oriented forums distributed by email. These are administered by software

programs. Probably the most common program is the listserv. A great variety

of topics are covered by listserv, many of them academic in nature. When you

subscribe to a listserv, messages from other subscribers are automatically sent

to your electronic mailbox. You subscribe to a listserv by sending an e-mail

message to a computer program called a list server. List servers are located on

computer networks throughout the world. This program handles subscription

information and distributes messages to and from subscribers. You must have

an e-mail account to participate in a listserv discussion group. Visit Tile.net at

http://tile.net/ to see an example of a site that offers a searchable collection of

e-mail discussion groups.

UseNet News

Usenet News is a global electronic bulletin board system in which

millions of computer users exchange information on a vast range of topics. The

major difference between Usenet News and e-mail discussion groups is the fact

that Usenet messages are stored on central computers, and users must connect

to these computers to read or download the messages posted to these groups.

This is distinct from e-mail distribution, in which messages arrive in the

electronic mailboxes of each list member.

Usenet itself is a set of machines that exchanges messages, or articles,

from Usenet discussion forums, called newsgroups. Usenet administrators

control their own sites, and decide which (if any) newsgroups to sponsor and

which remote newsgroups to allow into the system. There are thousands of

Usenet newsgroups in existence. While many are academic in nature, numerous

newsgroups are organized around recreational topics. Much serious computer-

related work takes place in Usenet discussions. A small number of e-mail

discussion groups also exist as Usenet newsgroups. The Usenet news feed can

be read by a variety of newsreader software programs. For example, the

Netscape suite comes with a newsreader program called Messenger.

Newsreaders are also available as standalone products.

Chat and Instant Massaging

Chat programs allow users on the Internet to communicate with each

other by typing in real time. They are sometimes included as a feature of a Web

site, where users can log into the “chat room” to exchange comments and

information about the topics addressed on the site. Chat may take other, more

wide-ranging forms. For example, America Online is well known for

sponsoring a number of topical chat rooms. Internet Relay Chat (IRC) is a

service through which participants can communicate to each other on hundreds

of channels. These channels are usually based on specific topics. While many

topics are frivolous, substantive conversations are also taking place. To access

IRC, you must use an IRC software program.

A variation of chat is the phenomenon of instant messaging. With

instant messaging, a user on the Web can contact another user currently logged

in and type a conversation. Most famous is America Online’s Instant

Messenger. ICQ, MSN and Yahoo are other commonly-used chat programs.

Evolution of Internet

The history of the Internet begins at the height of the cold war in the

1960’s. People at the Rand Corporation, America’s foremost military think

tank, were trying to figure out an important strategic problem: how could US

authorities talk to each other in the aftermath of a nuclear attack?

Communication networks of the day were chained point-to-point, with each

place on the network dependent on the link before it. If one point in the

network was blown up, the whole network would become useless. Paul Baran,

one of the Rand thinkers on the project, conceived the idea for a new kind of

communications network; one that wasn’t organized point-to-point, but instead

was set up more like a fishnet. He believed this structure could allow

information to find its own path through the network even if a section had been

destroyed. His eleven volume report for the Pentagon was eventually shelved;

but younger engineers realized that he had hit on an essential idea. Baran’s

Cold War musings later influenced the design used to create a small,

decentralized network connecting computers at four university campuses

around the United States. This tiny seed eventually grew into the Internet; a

huge network-of networks, millions of nodes strong, which today covers the

entire globe. The Internet has come a long way from its military beginnings.

Touching almost every aspect of society, it is now more likely to be used to

plan a family vacation than to transmit military secrets. Following are

highlights of the 30 year history of the Internet; how it grew, what technologies

grew with it, and the impact of success on the Internet itself.

1962 - 1969

The Internet is first conceived in the early ’60s. Under the leadership of

the Department of Defense’s Advanced Research Project Agency (ARPA), it

grows from a paper architecture into a small network (ARPANET) intended to

promote the sharing of supercomputers amongst researchers in the United

States.

� 1962 – The RAND Corporation begins research into robust, distributed

communication networks for military command and control.

� 1965 - ARPA sponsors research into a “cooperative network of time-

sharing computers.”

� 1967 - Delegates at a symposium for the Association for Computing

Machinery in Gatlinburg, TN discuss the first plans for the ARPANET.

� 1969 - Researchers at four US campuses create the first hosts of the

ARPANET, connecting Stanford Research Institute, UCLA, UC Santa

Barbara, and the University of Utah.

1970 - 1973

The ARPANET is a success from the very beginning. Although

originally designed to allow scientists to share data and access remote

computers, email quickly becomes the most popular application. The

ARPANET becomes a high-speed digital post office as people use it to

collaborate on research projects and discuss topics of various interests.

� 1971 - The ARPANET grows to 23 hosts connecting universities and

government research centers around the country.

� 1972 - The Inter Networking Working Group becomes the first of

several standards-setting entities to govern the growing network. Vinton

Cerf is elected the first chairman of the INWG, and later becomes

known as a “Father of the Internet.”

� 1973 - The ARPANET goes international with connections to

University College in London, England and the Royal Radar

Establishment in Norway.

1974 - 1981

The general public gets its first vague hint of how networked computers

can be used in daily life as the commercial version of the ARPANET goes

online. The ARPANET starts to move away from its military/research roots. ·

1974 - Bolt, Beranek & Newman opens Telnet, the first commercial version of

the ARPANET.

� 1976 - Queen Elizabeth goes online with the first royal email message.

� 1979 - Tom Truscott and Jim Ellis, two graduate students at Duke

University, and Steve Bellovin at the University of North Carolina

establish the first USENET newsgroups. Users from all over the world

join these discussion groups to talk about the net, politics, religion and

thousands of other subjects.

� 1981 - ARPANET has 213 hosts. A new host is added approximately

once every 20days.

1982 - 1987

Bob Kahn and Vinton Cerf are key members of a team which creates

TCP/IP (Transmission Control Protocol/Internet Protocol: TCP makes sure data

arrives correctly and in the proper order. IP specifies the way in which data will

be communicated between two computers on a network), the common

language of all Internet computers. For the first time the loose collection of

networks which made up the ARPANET is seen as an “Internet”, and the

Internet as we know it today is born. The mid-80s marks a boom in the

personal computer and super-minicomputer industries. The combination of

inexpensive desktop machines and powerful, network-ready servers allows

many companies to join the Internet for the first time. Corporations begin to

use the Internet to communicate with each other and with their customers.

� 1982 - The term “Internet” is used for the first time.

� 1984 - William Gibson coins the term “cyberspace” in his novel

“Necromancer.” The number of Internet hosts exceeds 1,000.

� 1986 - Case Western Reserve University in Cleveland, Ohio creates the

first “Free net” for the Society for Public Access Computing.

� 1987-The number of Internet hosts exceeds 10,000.

1988 – 1990

By 1988 the Internet is an essential tool for communications; however it

also begins to create concerns about privacy and security in the digital world.

New words, such as “hacker,” “cracker” and” electronic break-in”, are created.

These new worries are dramatically demonstrated on Nov. 1, 1988 when a

malicious program called the “Internet Worm” temporarily disables

approximately 6,000 of the 60,000 Internet hosts.

� 1988 - The Computer Emergency Response Team (CERT) is formed to

address security concerns raised by the Worm.

� 1989 - System administrator turned author, Clifford Stoll, catches a

group of Cyber spies, and writes the best-seller “The Cuckoo’s Egg.”

The number of Internet hosts exceeds 100,000.

� 1990 - A happy victim of its own unplanned, unexpected success, the

ARPANET is decommissioned, leaving only the vast network-of-

networks called the Internet. The number of hosts exceeds 300,000.

1991 - 1993

Corporations wishing to use the Internet face a serious problem:

commercial network traffic is banned from the National Science Foundation’s

NSFNET, the backbone of the Internet. In 1991 the NSF lifts the restriction on

commercial use, clearing the way for the age of electronic commerce. At the

University of Minnesota, a team led by computer programmer Mark

MaCahillreleases “gopher,” the first point-and-click way of navigating the files

of the Internet in 1991. Originally designed to ease campus communications,

gopher is freely distributed on the Internet. MaCahill calls it “the first Internet

application my mom can use.” 1991 is also the year in which Tim Berners-Lee,

working at CERN in Switzerland, posts the first computer code of the World

Wide Web in a relatively innocuous newsgroup, “alt.hypertext.” The ability to

combine words, pictures, and sounds on Web pages excites many computer

programmers who see the potential for publishing information on the Internet

in a way that can be as easy as using a word processor. Marc Andreessen and a

group of student programmers at NCSA (the National Center for

Supercomputing Applications located on the campus of University of Illinois at

Urbana Champaign) will eventually develop a graphical browser for the World

Wide Web called Mosaic.

� 1991 - Traffic on the NSF backbone network exceeds 1 trillion bytes per

month.

� 1992 - The first audio and video broadcasts take place over a portion of

the Internet known as the “MBONE.” More than 1,000,000 hosts are

part of the Internet.

� 1993 - Mosaic, the first graphics-based Web browser, becomes

available. Traffic on the Internet expands at a 341,634% annual growth

rate.

1994 - 1996

As the Internet celebrates its 25th anniversary, the military strategies that

influenced its birth become historical footnotes. Approximately40 million

people are connected to the Internet. More than $1 billion per year changes

hands at Internet shopping malls, and Internet related companies like Netscape

are the darlings of high-tech investors. The Age of the Internet has arrived. ·

1994 - The Rolling Stones broadcast the Voodoo Lounge tour over the M-

Bone. Marc Andresen and Jim Clark form Netscape Communications Corp.

Pizza Hut accepts orders for a mushroom, pepperoni with extra cheese over the

net, and Japan’s Prime Minister goes online at www.kantei.go.jp. Backbone

traffic exceeds 10 trillion bytes per month. · 1995 - NSFNET reverts back to a

research project, leaving the Internet in commercial hands. The Web now

comprises the bulk of Internet traffic. The Vatican launches www.vatican.va.

James Gosling and a team of programmers at Sun Microsystems release an

Internet programming language called Java, which radically alters the way

applications and information can be retrieved, displayed, and used over the

Internet.

� 1996 - Users in almost 150 countries around the world are now

connected to the Internet. The number of computer hosts approaches 10

million.

Within 40 years, the Internet has grown from a Cold War concept for

controlling the tattered remains of a post-nuclear society to the Information

Superhighway. Just as the railroads of the 19th century enabled the Machine

Age, and revolutionized the society of the time, the Internet takes us into the

Information Age, and profoundly affects the world in which we live. Today

some people telecommute over the Internet, allowing them to choose where to

live based on quality of life, not proximity to work. Many cities view the

Internet as a solution to their clogged highways and fouled air. Schools use the

Internet as a vast electronic library, with untold possibilities. Doctors use the

Internet to consult with colleagues half a world away. And even as the Internet

offers a single Global Village, it threatens to create a 2nd class citizenship

mongo those without access. As a new generation grows up as accustomed to

communicating through a keyboard as in person, life on the Internet will

become an increasingly important part of life on Earth. The evolution of the

Internet can at best be described as a phenomenon. It had gone from near

invisibility to near ubiquity in only a short period. The sad conclusions that

many people may draw lead them to believe that since the Internet became

popular overnight, it was created overnight. The ignorance of the common

citizen unfortunately does no justice to the hard work and efforts of the many

scientists, students, and intellectuals who collaborated and created this

technological masterpiece covering the world called the Internet.

Internet Working

How the Internet Works

The Internet is the world’s largest distributed system; it was designed

and engineered for redundancy (it has an abundance of routes and connections)

and resilience (it easily recovers from a mishap). The Internet is not a single

company or a group of companies, nor even a single network. It is a worldwide

mesh or matrix of hundreds of thousands of networks, owned and operated by

hundreds of thousands of people in hundreds of countries, all interconnected by

about 8,000 ISPs (Internet Service Providers). No single organization controls

the Internet; not the U.N.; not the biggest ISPs; and the Internet has long since

outgrown control by the U.S. government.

The Internet is different from other major services. Electricity tends to

be provided by a single company in each geographical area. The “last mile” of

telephone service to the customer is usually owned by a single company. But in

general there is more than one Internet provider in any locale, and there are

usually many paths from a local provider in one area to a provider in another

area.

When you, the user, look at a web page through the Internet, many

things happen along the way. There are various ways to get from your house or

office through the “last mile” to the Internet: modem dialup, ISDN, DSL, cable

modem, wireless, leased line, etc. These various technical methods may

provide speeds anywhere from very slow (a few hundred bits per second) to

very fast (billions of bits per second). All these access methods are onramps to

the information superhighway.

In order to transmit text or pictures, your data is chopped up into small

packets which are routed through the Internet. But first they have to go from

you to your local ISP, or the equivalent piece of the Internet inside your

organization (an intranet). This local ISP is a possible point of failure. If

something goes wrong at your local ISP, it may look to you like the Internet is

broken. It’s not. Only one small piece of it is broken. The rest of the Internet,

with its portals and stock portfolios and shops and reams of scientific data and

plethora of information and people on it will not break because one ISP does.

To reach a web server, your local ISP sends your packets of data to another

ISP, which may send them to another ISP, or through an Exchange Point (IX)

or a National Access Point (NAP) or Local Access Point (LAP) to get to

another ISP. Thus your packets pass through a chain of ISPs through nodal

points to reach their destination. Your packets may pass through fiber optic

cables in the ground, satellites in the sky, undersea cables, or radio links. They

may travel at speeds including T-1 (1.544 Mbps), T-3 (45Mbps), or faster (or

slower). The Internet Protocol (IP) ties all of those links together, enabling your

packets travel through the Internet.

Eventually your packets arrive at the web server, and the web server

sends responses back along a similar path (almost definitely not the same one).

Any of these Internet providers can have problems (congestion, broken link,

power outage, broken computer, etc.), which may cause the web server to seem

slow or unresponsive to you. But the web server is broken only if the web

server is actually broken. Problems in intervening parts of the Internet do not

break the web server, which may well be accessible to other people, and may

become accessible to you as soon as the various Internet providers route your

traffic around problems. Much rerouting in the Internet is dynamic, and

happens automatically. (Imagine you are driving up the California coast and

come to a sign that says that there has been a mudslide. You drive inland, north

on another road, perhaps rejoining the coastal highway again. You have

changed your route dynamically.) Some rerouting isn’t automatic. In particular,

the biggest ISPs, frequently called backbones, cover vast geographical areas

and carry large proportions of the Internet’s traffic. A failure in a backbone or

in one of the major interconnection points between them can affect many

Internet users. And such a problem may take some time to be resolved, as the

biggest ISPs often prefer to manually examine changes in major routes before

implementing them. But longstanding observation of the Internet indicates that

“some time” is normally at most few hours, even in the face of the biggest

problems.

Internet providers use the same methods for routing packets for

electronic mail or file transfers or remote login or voice or video. People tend

to be quicker to notice slowness in accessing web pages, so we have used

accessing a web server as an example. There are other key pieces of the

Internet, most notably the root name servers. Name servers translate domain

names, such as www.ripe.net, into the IP addresses, such as 193.0.0.195, that

are used by the Internet protocols in carrying your packets through the Internet.

The root name servers handle the most basic part of that translation, which is

finding name servers for the top level domains (TLDs), such as NET, COM,

ORG, EDU, GOV, FR (France), JP (Japan), AU (Australia), or PE (Peru). The

root name servers are widely spaced in both geography and in Internet

topology, so that a failure in one cannot readily affect another. The root name

server operators have also cooperated in extensively testing their software,

hardware, and capacities, and they all know how to reach each other in case

they perceive problems. The rest of the Domain Name Service (DNS) is

distributed among hundreds of thousands of name servers for the various

domains. For example, there are name servers for ORG, and then there are

name servers for MIDS.ORG. Every domain is supposed to have at least two

independent name servers, and most do (another instance of redundancy). In

any case, a failure in a single name server may make a particular domain

temporarily inaccessible, but it will not affect the Internet at large.

The decentralization of the Internet is one of its biggest advantages and

one of its most basic features, designed into its protocols from the beginning

and tested in practice over many years. If one piece breaks, that doesn’t mean

the Internet is broken. And decentralization requires cooperation, so the various

ISPs and IXes and the like are accustomed to cooperating with one another to

fix and prevent problems. It is this decentralization and cooperation that has

permitted the Internet to grow faster for longer than any other technological

phenomenon in history. It is important for you, the user, to understand how

decentralization makes the Internet work, so that you will know that the

Internet is actually very hard to break.

Internet Services

Some of the most popular Internet services include electronic mail (e-

mail), the World Wide Web (WWW), Chat, Internet News, File Transfer

Protocol (FTP), and Telnet.

Electronic mail (e-mail)

E-mail is the most popular service on the Internet. You can use it to send

messages to any user connected to the Internet.

World Wide Web (WWW)

The World Wide Web, or the Web, is a term used to describe the

interlinked collection of hypertext documents and multimedia content available

on the Internet. Hypertext documents are files that have been formatted for use

on the Internet. You use a Web browser, such as Microsoft Internet Explorer, to

search for, locate, view, and download information from the Internet.

Chat

Chat programs allow you to participate in a real-time conversation with

two or more people on the Internet.

Internet News

Internet News is a service that hosts electronic discussion groups

through which participants can share information and opinions. A news client,

such as Microsoft Outlook® Express, can then be used to access these groups.

File Transfer Protocol (FTP)

FTP is a service that includes a server for transferring files from the

server to a client computer. Users can download files from the FTP server by

using an FTP client utility.

Telnet

Telnet offers a way to remotely log on to a computer and work on that

computer. By logging on to this computer remotely, users can access services

or resources that they may not have on their own workstation.

Internet Access Methods

Connections to the Internet can be described in four basic categories:

dialup, proxy, direct and leased.

A dialup connection

A dialup connection is attained through a modem or similar device. The

connection typically provides between 2400 bps (bits per second) and 28,800

bps throughputs, which is usually more than adequate for e-mail and for

running processes on the remote host. While this type of connection is usually

adequate for line-oriented access, it is not suitable for full-screen programs. For

instance, utilities such as Mosaic expect to be able to address the full screen of

a machine that is directly connected to the internet. To make full use of many

of the current Internet resources, then, a more advanced connection is

required—at minimum, a proxy connection.

A proxy connection

A proxy connection is also typically made through a modem, but it has

special provisions that enable full Internet access. SLIP (Serial Line IP) and

PPP (Point-to-Point Protocol) are two examples of such provisions (both

discussed later in this chapter). Tools such as FTP, Gopher and Mosaic are

thereby available for use just as if the connection were directly on the Internet.

Direct connections

Direct connections are obtained when the machine being used has a

dedicated circuit to the Internet. This can still be a remote connection, but it has

the full functionality of a directly connected machine. A good example is ISDN

(Integrated Services Digital Network), which is discussed later in this chapter.

Leased line

Lastly, the leased line is a circuit leased from the local telephone

company that provides a permanent address on the Internet. The advantage of a

permanent address is that it that enables services such as FTP or Gopher to be

set up. The leased line varies in throughput from 9600 bps to 45,000,000 bps

(45 Mbps).

Internet Service Provider

ISP definition

An Internet Service Provider, or ISP, is a company that provides its

customers with access to the Internet. Customers may connect to their ISP

through dialup (telephone), broadband (including DSL, ISDN and cable

modem services), or wireless connections. There are countless national and

regional ISPs, and a great many websites exist to help you locate the best one

for you. There are many different ISP’s which provide a broad variety of

services at a broad variety of prices. An ISP has the equipment and the

telecommunication line access required to have a point-of-presence on the

Internet for the geographic area served.

The larger ISPs have their own high-speed leased lines so that they are

less dependent on the telecommunication providers and can provide better

service to their customers. Among the largest national and regional ISPs are

AT&T WorldNet, IBM Global Network, MCI, Netcom, UUNet, and PSINet.

ISPs also include regional providers such as New England’s NEAR Net and the

San Francisco Bay area BAR Net. They also include thousands of local

providers. In addition, Internet users can also get access through online service

providers (OSP) such as America Online and CompuServe. The larger ISPs

interconnect with each other through MAE (ISP switching centers run by MCI

WorldCom) or similar centers. The arrangements they make to exchange traffic

are known as peering agreements. There are several very comprehensive lists

of ISPs world-wide available on the Web. An ISP is also sometimes referred to

as an IAP (Internet access provider).

ISP is sometimes used as an abbreviation for independent service

provider to distinguish a service provider that is an independent, separate

company from a telephone company.

The Types and Functions of Modems

The Origin of Modems

The word “modem” is a contraction of the words modulator-

demodulator. A modem is typically used to send digital data over a phone line.

The sending modem modulates the data into a signal that is compatible with the

phone line, and the receiving modem demodulates the signal back into digital

data. Wireless modems convert digital data into radio signals and back.

Modems came into existence in the 1960s as a way to allow terminals to

connect to computers over the phone lines. A typical arrangement is shown

below:

In a configuration like this, a dumb terminal at an off-site office or store

could “dial in” to a large, central computer. The 1960s were the age of time -

shared computers, so a business would often buy computer time from a time-

share facility and connect to it via a 300-bit-per-second (bps) modem. A dumb

terminal is simply a keyboard and a screen. A very common dumb terminal at

the time was called the DEC VT-100, and it became a standard of the day (now

memorialized in terminal emulators worldwide). The VT-100 could display 25

lines of 80 characters each. When the user typed a character on the terminal,

the modem sent the ASCII code for the character to the computer. The

computer then sent the character back to the computer so it would appear on

the screen. When personal computers started appearing in the late 1970s,

bulletin board systems (BBS) became the rage. A person would set up a

computer with a modem or two and some BBS software, and other people

would dial in to connect to the bulletin board. The users would run terminal

emulators on their computers to emulate a dumb terminal.

IP Addressing

What Is an IP Address?

Each TCP/IP host is identified by a logical IP address. A unique IP

address is required for each host and network component that communicates by

using TCP/IP. The IP address identifies a system’s location on the network in

the same way that a street address identifies a house on a city block. Just as a

street address must identify a unique residence, an IP address must be globally

unique and have a uniform format.

Network ID

Each IP address defines the network ID and host ID. The network ID

identifies the systems that are located on the same physical segment. All

systems on the same physical segment must have the same network ID. The

network ID must be unique to the internet work.

Host ID

The host ID identifies a workstation, server, router, or other TCP/IP host

within a segment. The address for each host must be unique to the network ID.

Network ID and Host ID

Each IP address is 32 bits long and is composed of four 8-bit fields,

called octets. Octets are separated by periods. The octet represents a decimal

number in the range 0–255. This format is called dotted decimal notation. The

following is an example of an IP address in binary and dotted decimal formats.

Internet Domains

In the old days, where the Internet barely had 200 hosts, every host

knew the address of every other host on the Internet. Every host also associated

a human-readable name with every other host’s IP address so that the user

didn’t have to remember all those numbers. Now the Internet has millions of

hosts connected to it, however, so keeping track of every host on every

computer isn’t just impractical, it’s impossible. You certainly can access a host

by its IP address. For example, to access my host, you’d use 206.50.127.46. To

access Macmillan’s host, you’d use 206.246.150.10. Why use an IP address,

however, when you can use a domain name instead? A domain name is a

unique, human- readable name for a host on the Internet. Domain names are

case sensitive, by the way. For example, honeycutt.com, mcp.com, and

microsoft.com are examples of domain names.

Domain names are divided into parts with a period, just like an IP

addresses. Whereas an IP address gets more specific as you look from left to

right, domain names get more specific as you look from right to left. In general,

domain names follow this format: hostname. Second-level. first-level

First-level. The first-level domain is the least specific. You’ll see first-

level domains like com and uk, which represent the type of organization or

country in which the host belongs. Table 2.1 describes some of the first-level

domains that are typical on the Internet. First-level domains are also called

zones or top-level domains. Second-level The second-level domain identifies

the organization that owns or operates the network to which the host is

attached. Every organization that has a network attached to the Internet has

registered their second-level domain. The name usually represents the

company’s name or trade. For example: microsoft.com, honeycutt.net, and

whitehouse.gov. Host-name The host-name identifies the host on the network

represented by the first- and second-level domains. The host-name isn’t

registered because the network on which the host resides worries about routing

traffic to the host based upon its name. That is, the only information that the

Internet’s routers need to route traffic to the host is the first- and second-level

domains. The host’s network worries about routing traffic to the host given its

host-name.

First-Level Domain Names

Name Description

.com Commercial and for-profit organizations

.edu Universities & Education Organization

.gov Federal government agencies

.mil U.S. military sites

.net Internet infrastructure and service providers

.org Miscellaneous and non-profit organizations

TCP/IP Protocol

TCP/IP (Transmission Control Protocol/Internet Protocol) is the basic

communication language or protocol of the Internet. It can also be used as a

communications protocol in a private network (either an intranet or an

extranet). When you are set up with direct access to the Internet, your computer

is provided with a copy of the TCP/IP program just as every other computer

that you may send messages to or get information from also has a copy of

TCP/IP. TCP/IP is a two-layer program. The higher layer, Transmission

Control Protocol, manages the assembling of a message or file into smaller

packets that are transmitted over the Internet and received by a TCP layer that

reassembles the packets into the original message. The lower layer, Internet

Protocol, handles the address part of each packet so that it gets to the right

destination. Each gateway computer on the network checks this address to see

where to forward the message. Even though some packets from the same

message are routed differently than others, they’ll be reassembled at the

destination. TCP/IP uses the client/server model of communication in which a

computer user (a client) requests and is provided a service (such as sending a

Web page) by another computer (a server) in the network. TCP/IP

communication is primarily point-to-point, meaning each communication is

from one point (or host computer) in the network to another point or host

computer. TCP/IP and the higher-level applications that use it are collectively

said to be “stateless” because each client request is considered a new request

unrelated to any previous one (unlike ordinary phone conversations that require

a dedicated connection for the call duration). Being stateless frees network

paths so that everyone can use them continuously. (Note that the TCP layer

itself is not stateless as far as any one message is concerned. Its connection

remains in place until all packets in a message have been received.)

Many Internet users are familiar with the even higher layer application

protocols that use TCP/IP to get to the Internet. These include the World Wide

Web’s Hypertext Transfer Protocol (HTTP), the File Transfer Protocol (FTP),

Telnet (Telnet) which lets you logon to remote computers, and the Simple Mail

Transfer Protocol (SMTP). These and other protocols are often packaged

together with TCP/IP as a “suite.” Personal computer users usually get to the

Internet through the Serial Line Internet Protocol (SLIP) or the Point-to-Point

Protocol (PPP). These protocols encapsulate the IP packets so that they can be

sent over a dial-up phone connection to an access provider’s modem. Protocols

related to TCP/IP include the User Datagram Protocol (UDP), which is used

instead of TCP for special purposes. Other protocols are used by network host

computers for exchanging router information. These include the Internet

Control Message Protocol (ICMP), the Interior Gateway Protocol (IGP), the

Exterior Gateway Protocol (EGP), and the Border Gateway Protocol (BGP).

The Intranet

An intranet shares most of the characteristics of the Internet, but in at

least one way, it’s fundamentally different. And just as the Internet has had

profound effect on how we communicate, intranets have transformed the

business world as well. Both Fortune 500 companies and small businesses have

implemented this infrastructure, improving productivity while reducing costs.

Just what is an intranet? Think of it as a mini-Internet designed to be used

within the confines of a company, university or organization. What

distinguishes an intranet from the freely accessible Internet is that intranets are

private.

Evolution of WWW

Ever since the Internet merged as an emblem in our mind, the World

Wide Web (WWW) has been exploding into all the aspects of our work, studies

and leisure life. Within the employment market, jobs requiring knowledge of

the Web, Internet and e-Commerce have been most in demand from both

employer and employee’s perspectives. As an employer or employee coping

with the ever changing IT work environment, you should have a fair

understanding of the history, development, capabilities and the future of

WWW. In a series of informative articles, I will introduce all issues associated

with the World Wide Web from the employment perspective. Here I begin with

the 30-year evolution of WWW to preface the series.

Client/Server computing

Increasing numbers of users have to share data. Programs are divided

into two parts: client and server.

1. Client applications that run on local machines allow users to manipulate

centralized data.

2. Server applications that run on centralized machines coordinate sharing

of the data amongst many users.

Middleware software provides transparency between servers and clients

in three-tier client/server systems.

The Internet

The attempts to connect all private and public networks are successful

with the appearance of the Internet. Internet Protocol (IP) becomes a de-facto

standard network protocol of exchanging data between various networks.

Transport Control Protocol (TCP) becomes a de-facto standard transport

protocol on top of IP. Their combination is referred to as the TCP/IP standard.

The World Wide Web

WWW originated as a framework for electronic publishing of hypertext.

1. HTML – Hypertext Markup Language.

2. HTTP – Hypertext Transfer Protocol.

The scope of content published on the Web pages expands daily and

includes text, graphics, sound and video. A Web browser is becoming a new

operating system for many users. Other traditional network applications like

email, file transfer, telnet/remote login have been incorporated under the same

browser roof with the Universal Resource Locator (URL). New business

opportunities have emerged in electronic publishing and commerce. New

technologies like search engines, agents, etc., mix with not-so-new ones like

data mining to address arising challenges. Any user can access any computer

anywhere in the world using the Internet.

Connecting to Internet

How to Connect to the Internet

Before you can connect to the Internet and access the World Wide Web,

you need to have certain equipment. In brief, you must have a computer

(preferably running an up to- date operating system); a modem and access to a

telephone line or a local area network (LAN) that is in turn connected to the

Internet; and connection software that will allow you to establish an account

with a service provider and access the Internet. A modem is not needed when

accessing the Internet through a LAN

The Right Hardware

To operate most of the current Web browsers and on-line services, you

should have an IBM PC/PC equivalent, UNIX workstation, or Apple

Macintosh computer with at least 8 megabytes (MB) of random access

memory (RAM) and 10 MB of free disk space. If you are unsure of how much

RAM and disk space your computer has, consult your user’s manual. For best

results, use a PC with a 486 or Pentium microprocessor; or a Macintosh with a

030, 040 or PowerPC microprocessor. It is possible to connect to the Internet

using a computer other than an IBM PC, Macintosh or UNIX workstation,

though the access software available for such machines is limited. If you are

accessing the Internet outside of a LAN environment, you will need a modem

that will connect you with other computers and interpret the data being sent

back and forth. Most any modem that is compatible with your computer will

do, though the higher the kilobits per second (kbps) rate of your modem, the

faster it will transmit data. Modem speed is an important consideration when

accessing sites on the Web that contain lots of digitized data. In general, your

modem should transmit data at 14.4 kbps or faster to give you optimum

performance on the Web. If you are looking to purchase a modem, buy the

fastest model you can afford. You must also have access to a live telephone

line. Most modems accept the same jacks as do ordinary household telephones,

allowing you to connect your modem to a wall jack using standard phone cord.

Some cable TV providers have begun offering Internet connections via cable.

Such connections provide much faster transmission speeds than standard phone

lines, though you will need a special modem that allows you to link your

computer with the cable. If you are interested in a cable Internet connection,

contact your local cable operator to see if the service is available in your area.

You can also connect to the Internet through a LAN with Internet access. If

you are unsure as to the capacities of your LAN to do this, contact your site’s

systems administrator

The Right Software

For best results, make sure that your computer is running the most up-

to-date operating system that it can handle. If you have an IBM PC/PC

compatible computer, it should be running Microsoft Windows version 3.1,

Windows NT, Windows 95 or OS/2. If you have a Macintosh, it should be

running System 7 or higher. To make your connection complete, you will need

connection software that allows your computer to dial into an Internet access

provider, establish an account, and work with the data in a straightforward

manner. Many access providers will give you software that will allow you to

access their systems using an all-in-one custom interface. Others may give you

a collection of separate software packages that can be used together. But

whatever software they provide, be sure that it is compatible with your

computer and operating system before attempting to use it.

Some Internet access providers may allow you to establish a serial line

interface protocol (SLIP) or point-to-point protocol (PPP) connection, either of

which essentially makes your computer a part of the Internet. Unlike many

standard dial-up software packages, a SLIP/PPP connection allows you to run

independent software packages such as Web browsers, either one at a time or

simultaneously.

The Browser

As you surf the Web, you will come across sites that state, “This site is

best viewed with…” and then name a particular browser. Many will even

provide a link to a site where you can download the specified browser. Sites

make these recommendations because some browsers use special protocols,

allowing site creators to offer extra features beyond the standard capabilities of

hypertext markup language (HTML). Chief among these browsers are Netscape

Navigator and Microsoft Internet Explorer. Your Internet service provider will

most likely give you a choice of browsers so try out a couple, and use the

browser that best suits your needs.

Connection Options

Until recently, the two primary methods of accessing the Internet were

through a network connection, allowing users of local area networks (LANs)

to go online through their school or workplace systems, and dial-up

connections through a modem and phone line. However, new connection

options allow for greater speeds and flexibility, while keeping costs to a

minimum. The following are some of the newer connection options that you

might want to investigate: · Cable Internet—these systems allow your

computer to connect to the Internet through the same cable that carries your TV

signal. Monthly service charges are usually not much more than standard

modem connection costs, but you have to rent or purchase a “cable modem.”

Additionally, your computer will need an Ethernet card (a special circuit board

that allows for network connections). Not all cable service operators offer this

service; call your local operator for more information.

Web Browsers

The World Wide Web (WWW), or Web, is the portion of the Internet

that provides links to graphical content. The Web has developed into a network

of interactive documents that you can easily locate and read using various Web

browsers, such as Internet Explorer. A Web browser is a client application that

enables the client com putter to gain access to a Web server or other server,

such as an FTP server, running on the Internet. Web browsers can display text

files and various graphic and multimedia format files. A browser also interprets

and displays documents.

Web Servers

Web server is a program that, using the client/server model and the

World Wide Web’s Hypertext Transfer Protocol (HTTP), serves the files that

form Web pages to Web users (whose computers contain HTTP clients that

forward their requests).

Every computer on the Internet that contains a Web site must have a

Web server program. Two leading Web servers are Apache, the most widely-

installed Web server, and Microsoft’s Internet Information Server (IIS). Other

Web servers include Novell’s Web Server for users of its NetWare operating

system and IBM’s family of Lotus Domino servers, primarily for IBM’s

OS/390 and AS/400 customers.

A client computer connects to the Internet or an intranet by using a Web

browser to find information stored and organized on a Web server. A Web

server is a computer that uses TCP/IP to send Web page content to client

computers over a network. A Web server communicates with clients by using

an appropriate protocol, such as HTTP or HTTPS. The terms Web server and

HTTP server are synonymous, because URLs identifying data on a Web server

begin with http. For example, the Microsoft Web site is

http://example.microsoft.com/. Every Web server has an IP address and

perhaps a domain name. For example, when you enter the URL

http://example.microsoft.com/webpage.htm in your Web browser, it sends a

request to the Web server with the domain name microsoft.com. Then the Web

server locates and retrieves the page ms.htm, and sends it to your browser. Web

servers often come as part of a larger package of Internet- and intranet-related

programs for serving e-mail, downloading requests for File Transfer Protocol

(FTP) files, and building and publishing Web pages. Considerations in

choosing a Web server include how well it works with the operating system

and other servers, its ability to handle server-side programming, security

characteristics, and publishing, search engine, and site building tools that may

come with it.

Proxy Servers

Most home and small office networks use a dial-up or modem network

connection to an ISP, which in turn connects them to the Internet. The ISP

assigns a single IP address to each network for connecting to the Internet. In

addition, each computer in a network requires an IP address for Internet

connection. Rather than using separate IP addresses for each computer, it is

more cost-effective to use a single IP address for multiple computers. A proxy

server is a firewall component that enables you to connect multiple computers

in a network to the Internet by using a single IP address. Proxy servers have

two main functions: to improve network performance and filter client requests.

Domain Name Server

The Domain Name System (DNS) is a global network of servers that

translate host names like www.internic.net into dotted numerical IP (Internet

Protocol) addresses, like 198.41.0.6 A DNS server is just a computer that’s

running DNS software. DNS software has two parts:

1. The actual name server

2. A resolver.

The name server responds to browser requests by supplying name-to-

address conversions. When it doesn’t know the answer, the resolver will ask

another name server for the information. When you type in a URL, your

browser sends a request to the closest name server. If that server has recently

had a request for the same host name, it will locate the information in its cache

and reply. If the name server is unfamiliar with the domain name, the resolver

will ask another nameserver. If that doesn’t work, the second server will ask

yet another - until it finds one that knows.

Once the information is located, it’s passed back to your browser, and

you are sent to the web site for the URL you entered. Usually this process

occurs quickly, but sometimes it takes several seconds. Occasionally, you will

get a dialog box that says the domain name doesn’t exist, even though you

know it does. This happens because of delays in one name server replying to

another, and your computer times out, dropping the connection. Often, if you

try again, you will get to the web site you are looking for on the second try.

This is because the nameserver with the information has had enough time to

reply, and your name server has now stored the information in its cache.

Hypertext

Hypertext is a text which contains links to other texts. The term was

invented by Ted Nelson around 1965. Hypertext is therefore usually non-linear

(as indicated below). Hypertext allows movement through a document in a

non-linear fashion. As such, it is a departure from a book and other “written”

material. The user can “navigate” through the use of links. These links may be

selected through a keyboard, a mouse, a touch screen or some other input

device. In all cases, a microprocessor is used. Hypertext documents are

prepared using an authoring tool. The most common authoring tool is probably

Hypertext Markup Language (HTML) However; there are other well known

authoring tools such as Author ware and Toolbox. Standard General Markup

Language that can also be used.

Technically speaking hypertext is a link you click on to get from one

page to another when surfing the internet (or an intranet). The pictures and

phrases that make up the links are called hypertext links. Any time you click on

something on a web site you are actively using hypertext. The hypertext we

want to look at here is a type of electronic genre for writing. We want to give

you some ideas of how you can use hypertext in the classroom and as a

publishing medium.

Hyperlinks

A hyperlink is a reference to another location within the existing HTML

document or in a new HTML document. The data of the HTML document or

object can be stored in file system file server on the Internet (referred to by

URLs), or any arbitrary location that can be referenced How a hyperlink is

presented to the user is up to the hyperlink container and the context of the

hyperlink. It is common for hyperlinks to be presented as colored, underlined

text, as hotspot regions on an image, or as pushbuttons. However, there are no

user interface requirements limiting the presentation of hyperlinks, although

guidelines suggest that they should be made obvious-via coloring, underlining,

or by changing the cursor or displaying tool tips when mouse over occurs. A

hyperlink is the same thing as a link. A link can be a picture or text or just

about anything on a web page. When something is a link, it simply means that

left clicking on it will lead you to a different place on the internet. This might

mean that you will be transferred to another page on the same web site. Or, it

might mean that you are transferred to a different site altogether. When a link is

embedded in text, the words composing the link are usually a different color

from the majority of text and most of the time, they are underlined.

URL (Universal Resource Locator)

Although a domain name provides a convenient way of referring to a

specific computer on the Internet, you rarely want to just connect to a

computer. More often, you want to retrieve information from a file on the

computer. To access a file on a computer connected to the Internet, you must

know the path to that file, known as its address. The addressing system

developed for this purpose is called a Uniform Resource Locator (URL).

What is a Domain Name?

Domains are the data that the Internet uses to identify specific “lots”

within the network. In their raw form, domains are numeric. I’m sure you’ve

seen this reflected in numeric URLs. Domain names are alphanumeric overlays

to the numeric component of a given domain. Essentially, they are the name of

the server on which the information resides. Systems Administrators get the

names from the Interknit how a name will be implemented are going to be up

to you and the server situation you are involved with. But, to some, having a

domain name is as much a part of their marketing strategy as other forms of

advertisement.

Domain Name Parts

Domains have two primary parts: the name and the suffix. Names can be

almost anything you want, although there are some character restrictions.

Typically, any combination of letters and numbers can be used to create the

name. This is followed by a suffix, which determines the type of organization

under which you register. General suffixes include

.com—Commercial organization (very common on the Web these days!)

.edu—Educational organization

.gov—Government institution

.mil—Military institution

.net—Network

.org—Organization

There are also country codes that fall into the suffix section of a domain.

Some examples include

.jp—Japan

.uk—Great Britain

.mx—Mexico

Search Engines

What are Search Engines?

Search engines are huge databases of web page files that have been

assembled automatically by machine. There are two types of search engines: ·

Individual. Individual search engines compile their own searchable databases

on the web. · Meta. Met searchers do not compile databases. Instead, they

search the databases of multiple sets of individual engines simultaneously It is

a program that searches documents for specified keywords and returns a list of

the documents where the keywords were found. Although search engine is

really a general class of programs, the term is often used to specifically

describe systems like Alta Vista and Excite that enable users to search for

documents on the World Wide Web and USENET newsgroups

Home Page

What is a Home Page?

For a Web user, the home page is the first Web page that is displayed

after starting a Web browser like Netscape’s Navigator or Microsoft’s Internet

Explorer. The browser is usually preset so that the home page is the first page

of the browser manufacturer. However, you can set it to open to any Web site.

For example, you can specify that “http://w.yahoo.com” or

“http://myweb.com” be your home page. You can also specify that there be no

home page (a blank space will be displayed) in which case you choose the first

page from your bookmark list or enter a Web address. For a Web site

developer, a home page is the first page presented when a user selects a site or

presence on the World Wide Web. The usual address for a Web site is the

home page address, although you can enter the address (Uniform Resource

Locator) of any page and have that page sent to you.

Web page images

Unless you are using a very new version of Internet Explorer as your

browser, saving a Web page will not include any images or animations that are

on the page - they are separate files. If the images on the Web page are an

important part of the content you wish to save to use offline, you must save the

images independently. To do so, right click the image (PC) or hold the mouse

down on the image (Mac) and select Save Picture as or Save Image As from

the pop-up menu. (If this option is not present in the pop-up menu, it is not a

standard image file that you can use offline - you are out of luck.) You will be

prompted with the Save dialog box as usual. It would be best to save the file

with the name and file type that is presented.

If you have saved the image file in the same location as the Web page

HTML file, there is a chance that you will see the image when you open the

Web page in your browser from your hard drive. If you do not see the image,

the Web page’s author must have used a different file hierarchy - you will have

to view the image separately from the Web page. Internet Explorer 5.0 will

give you an option to save the “Web page complete”, which means it will save

the page’s images with the HTML file for offline viewing.

E-mail

Electronic mail, or e-mail as it is more commonly known, is a paperless

method of sending letters, notes and messages from you to someone else or

even many people at the same time via the Internet. Electronic mail is very fast

compared to the post office. Your messages usually only take seconds to arrive

at their destination. You can send messages anytime and the message will be

available whenever the other person wants to look at it - even in the middle of

the night. But perhaps the biggest advantage to using e-mail is that it is cheap,

especially when sending messages to other states or countries. Today, it costs

the same to send e-mail to someone around the corner as it does to send the

message to a friend in a foreign country.

Advantages of Electronic Mail System

There are many remarkable features that make electronic email far

ahead of other telecommunication technologies. Back in 1992, there were only

2% of Americans use electronic mail systems in the United States. The

percentage went up to 15% today. It went up seven times within 5 years,

according to a survey by consultants Forrester. Forrester also estimated that

within the next five years more than half of the American population will be

using e-mail. The lists below are few major advantages that encourage people

to use electronic mail over other similar communication tools. · It can send

pictures, sounds, spreadsheet, and long document.

It costs users nothing - probably just the cost of a local phone call. · It is

fast. It can be arrived anywhere in the world within a few minutes. · It makes

clear and concise communication, avoids the risk of verbal misunderstanding.

Electronic mail is actually a wonderful tool that helps individuals and

companies work faster and smarter when productivity and efficiency is the key.

All of these advantages have helped employers to choose electronic mail

system as their major communication tool for internal and external use.

Protocols used

Common Internet protocols that enable you to access the Internet are

Hypertext Transfer Protocol (HTTP), HTTP Secure (HTTPS), File Transfer

Protocol (FTP), Simple Mail Transfer Protocol (SMTP), and Network News

Transfer Protocol (NNTP). In addition, Hypertext Markup Language (HTML)

and Dynamic HTML (DHTML) specify the formats of pages displayed on the

Web.

· HTTP

HTTP is a convention for sending messages from a server to a client by

using TCP/IP. HTTP communications are in plain text and not encrypted.

· HTTPS

HTTPS enables you to make a secure Web server connection by using

Secure Sockets Layer (SSL). SSL is an encryption technology that enables a

secure connection between a server and a client. The URLs for Web pages that

require an SSL connection start with https://.

· FTP

FTP enables you to transfer files between two computers on a network.

· SMTP

SMTP enables you to send e-mail over the Internet.

· NNTP

NNTP enables you to post, distribute, and retrieve messages on Internet

and intranet newsgroups.

· HTML

HTML is the standard language for creating and formatting Web pages.

HTML defines how text appears when viewed in a Web browser.

Mail Server

A mail server is a computer, or a software package, that provides a mail

service to client software running on other computers. There are main two

types of mail servers.

POP3 (Incoming) E-mail Server

Post Office Protocol 3 is the most recent version of a standard protocol

for receiving email. POP3 is a client/server protocol in which e-mail is received

and held for you by your Internet server. Periodically, you (or your client e-

mail receiver) check your mail-box on the server and download any mail.

POP3 is built into the Netscape and Microsoft Internet Explorer browsers.

POP3 accounts allow clients to have a private e-mail address where they can

exchange email with anyone they wish at anytime. Each POP3 email account

comes with its own login and password. The login is set by the characters

preceding the at sign “@” in the e-mail address. The password is determined by

the client when the POP3 account is setup.

SMTP (Outgoing) E-mail Servers

The ability to provide Email services to clients includes two critical

functions: SMTP and POP3. Together, they provide the means for clients to

send out-going mails and check for new incoming mail, respectively. SMTP

service is the side of Email that allows clients to send out-going E-mail

messages to any valid Email address. The SMTP server performs two basic but

important functions. First, it verifies that anyone attempting to send outgoing

E-mails through the SMTP server has the right to do so. Secondly, it sends the

out-going mails and if undeliverable, sends the message back to the sender.

You need to configure your Email client so that it knows what SMTP server to

use for sending outgoing E-mail messages. In order to send mails through the

proper SMTP servers, configure your e-mail client to access the SMTP (Out-

going Mails) Server: yourdomain.com.

Mail Addresses

Definition of Email Address and ID Terms

University Email Address

Address appearing in any public paper or electronic directories. This

address is used to protect the User ID from public view. Default format of this

address is ‘first name’.’ last name’@uky.edu. The portion of this address

before the ‘@’ may be modified by the owner.

Mailbox

Email system address to which email is redirected from the University

Email Address, stored and read by a user. Default format of this address is

‘User ID or other’@’email system identifier’.uky.edu. The ‘email system

identifier’ is not included in U-Connect accounts.

User ID:

This ID is used in conjunction with a password to permit a user to log

into an email system and access email in their mailbox.

Common Features in Netscape Communicator and Internet

Explorer

Internet Explorer and Netscape Communicator

Internet Explorer has migrated to the forefront as the preferred browser

because of the various applications used across the Internet by the University

System. Such programs as the PeopleSoft applications and various medical

programs used in the hospital enterprise require that Internet Explorer be used.

One thing to note is that Internet Explorer is installed by an automated process

that is established by ITS. For that reason, some functions are not accessible.

For example, endeavoring to change some the Options in Internet Explorer will

be impossible because the fields are grayed-out. The centralized installation

will also force some characteristics onto your workstation that have proven to

be an inconvenience to users. The only resolution is to make Internet Explorer

your default browser. The instructions for doing this are provided below.

Unfortunately, Internet Explorer is essentially a proprietary Microsoft product

and is not fully compliant with many of the international programming

standards used at many web sites. Netscape is often required to access some of

the features used at web sites. Until the compatibility issues are resolved, both

browsers will need to be supported and provided to users upon request.

The discussions presented below are frequent issues for users and

support personnel.

IT support will usually provide any assistance that is needed to resolve

compatibility issues between Internet Explorer and Netscape, but if help is not

immediately available the information below may prove useful.

Internet Explorer

How to Make Internet Explorer Your Default Browser

Follow these steps:

� Click on the Start button

� Select Settings

� Select Control Panel

� Select Internet Options

� Select the Program tab

� Check the box at the base of them window labeled “Internet Explorer

should check to see whether ....”

This usually does the trick. The next time Internet Explorer is activated,

it should present a query of whether you wish it to be your default browser.

Testing, however, has shown that this does not always work.

Conflicts between Internet Explorer and Netscape

Communicator

A recent update to Internet Explorer apparently generated a rash of lock-

ups whenever users attempted to open Netscape Communicator. Regardless of

what Microsoft says under oath, Internet Explorer is installed and updated by

Microsoft in a manner that seizes control of the Internet browser functions.

This causes considerable confusion for users and generates considerable cost in

supporting Netscape. As a consequence, the best solution is to let Internet

Explorer be your default browser and to install Netscape only if it is necessary

to utilize specific web pages.

Step#1, making Internet Explorer your default browser, is discussed

above. This usually works but there are cases where it does not work. If it fails,

proceed to Step #2.

Step #2 is to uninstall the Netscape program. This will clear out all

remnants of the Netscape program. To do so, follow these steps:

� Make certain all Internet browsers are closed.

� Go to the Department Applications/Setups/Applications menu.

� Click on the item titled “Netscape Communicator 4.75 Pre-Install.”

Running this program will backup your personal settings for Netscape

and clean out all Netscape program files and registry settings.

� Re-start your PC.

� After logging back onto the network, open Internet Explorer. If it asks

for you to make it the default browser, click “Yes.”

� To test how Internet Explorer will work, you may wish to bring up an e-

mail message that listed a website, click on that web site and see if

Internet Explorer is presented automatically.

Step #3 is necessary only if you wish to have Netscape re-installed.

� Make certain that all Internet browsers are closed.

� Return to the Department Applications/Setups/Applications menu.

� Run the item titled “Netscape Communicator 4.75”. This should re-load

a clean set of files for Netscape and refresh the registry.

� Open Netscape. A “profile manager” will be presented.

� Select “Default” and then press the “Start Communicator” button.

“Default” is the standard settings used by Netscape that accesses your

personal settings located in your personal directory on the server.

Importing Netscape Bookmarks

A common problem with moving to Internet Explorer is incorporating

the bookmarks you use in Netscape. This is fairly easy to do. Follow these

steps:

� Open Internet Explorer

� Select the “File” menu.

� Select “Import and Export”

� A window will be presented explaining what you can do with this

utility. Click the “Next” key.

� Select “Import Favorites.”

� Click the dot that says to Import from File or Address.

� File in the blank with the following: J:\Netscape\bookmark.htm

� For the destination, select the folder that has your login ID on it.

� Once the installation is complete your bookmarks will be imported into

the folder under your login ID.

Managing the Favorites Folder

The Favorites Folder in Internet Explorer is, unfortunately, a hodge-

podge of functions that could prove somewhat confusing. The oddity about

Internet Explorer is that it is the only program where personal settings do not

“roam.” In other words, the Favorites folder does not automatically copy to

your personal directory on our server and if you move to a different computer

your bookmarks will be missing. The following solutions have been employed

to solve that riddle. · First, some of the folders are imported automatically from

ITS. Most of these folders will pertain to commonly used University Hospital

web sites. Special attention should be provided to the folder titled “University

of Missouri Healthcare — Resources.” In it you will find several websites that

will provide useful services · The Department supplies an additional folder with

your login ID. This is where you should install your personal bookmarks.

� On a daily basis a program is executed that will endeavor to update your

personal bookmarks to your personal directory. The only bookmarks

updated, however, are those which reside under your ID.

� Feel free to remove folders that belong to other people. Their bookmarks

should be backed up into their personal directories.

� Research has been completed and testing will commence in late October

that will integrate the Favorites list into your personal profile. If tests

prove successful, management of Favorites should be much easier and

more intuitive.

Web Design Concerns

File Names

Web page editors are rather familiar with creating “hotlinks” to other

documents. You may wish to note, however, that Microsoft’s intuitive

“features” that are often included with Internet Explorer and other web design

tools can often create some problems with your final web document. One

particular area is file naming. The Internet is based on UNIX, a network

operating system. From UNIX, an internationally agreed standard of

programming was devised to make it possible to read documents, tables, and

images on any computer in the world. That standard was called HTML. That

standard does not permit spaces in file names. For example, if you create a

document in Microsoft Word and title it “Goals for 2001”, the only thing that

HTML or UNIX will read is “Goals”. The result is a failed hotlink. To correct

that problem, you must label the file as “Goals_for_2001”, replacing the space

with an underscore.

Writing effective Mail Messages

E-mail is a prized tool for the small entrepreneur. It allows you to

communicate quickly and frequently with your customer. It doesn’t matter that

your competitor can afford a fancy logo and expensive stationery. E-mail puts

you on an even footing. Without graphics or engraving to enhance your

message, what you say and how you say it matters even more than in print

communication. But because e-mail is so easy to send, and because as a harried

owner of a small business you feel pressured to respond immediately, you often

dash off a response on the fly. How many times have you clicked on “send”

and then remembered a couple of points you forgot to mention? Or did you

send a rambling message, giving your client the task of sorting it out? Did you

think your spelling didn’t matter? After all, “it’s only e-mail!” It matters a lot.

Your well-heeled competitor has the stature of his organization to back him up.

His misspellings will be chalked up to “too busy to spell check.” Your

misspellings and unorganized messages will call your competence into

question. Does your inattention to spelling reflect a similar disregard for

customer service? If your message is ill-conceived, can your product be any

better? When you write e-mail messages, remember your client will judge you

by what you say and how you say it. Don’t let your writing give your

customers a reason to turn to your competitor. Here are some guidelines to

enable you to write e-mail like the Fortune 500 pros.

THE NUMBTHE NUMBTHE NUMBTHE NUMBER SYSTEMSER SYSTEMSER SYSTEMSER SYSTEMS

The reason that "hex" and octal are popular in computing is that it's easy to

translate to and from the binary system that computers really use. People use

decimal primarily because they have ten fingers, but it's just not that convenient

to switch back and forth from 10011010010 to 1234. It IS convenient to

convert to 4D2 (hex) or 2322 (octal).

The numbers from decimal 0 through 15 in decimal, binary, octal, and

hexadecimal form are listed below.

DECIMAL BINARY OCTAL HEXA -DECIMAL

0 0 0 0

1 1 1 1

2 10 2 2

3 11 3 3

4 100 4 4

5 101 5 5

6 110 6 6

7 111 7 7

8 1000 10 8

9 1001 11 9

10 1010 12 A

11 1011 13 B

12 1100 14 C

13 1101 15 D

14 1110 16 E

15 1111 17 F

Binary

Binary describes a numbering scheme in which there are only two possible

values for each digit: 0 and 1. The term also refers to any digital

encoding/decoding system in which there are exactly two possible states. In

digital data memory, storage, processing, and communications, the 0 and 1

values are sometimes called "low" and "high," respectively.

Binary numbers look strange when they are written out directly. This is

because the digits' weight increases by powers of 2, rather than by powers of

10. In a digital numeral, the digit furthest to the right is the "ones" digit; the

next digit to the left is the "twos" digit; next comes the "fours" digit, then the

"eights" digit, then the "16s" digit, then the "32s" digit, and so on. The decimal

equivalent of a binary number can be found by summing all the digits.

For example, the binary 10101 is equivalent to the decimal 1 + 4 + 16 = 21

DECIMAL = 21 64 32 16 8 4 2 1

BINARY = 10101 0 0 1 0 1 0 1

Hexadecimal

Hexadecimal describes a base-16 number system. That is, it describes a

numbering system containing 16 sequential numbers as base units (including 0)

before adding a new position for the next number. (Note that we're using "16"

here as a decimal number to explain a number that would be "10" in

hexadecimal.) The hexadecimal numbers are 0-9 and then use the letters A-F.

We show the equivalence of binary, decimal, and hexadecimal numbers in the

table below.

Hexadecimal is a convenient way to express binary numbers in modern

computers in which a byte is almost always defined as containing eight binary

digits. When showing the contents of computer storage (for example, when

getting a core dump of storage in order to debug a new computer program or

when expressing a string of text characters or a string of binary values in

coding a program or HT ML page), one hexadecimal digit can represent the

arrangement of four binary digits. Two hexadecimal digits can represent eight

binary digits, or a byte.

Octal

Octal (pronounced AHK-tuhl, from Latin octo or "eight") is a term that

describes a base-8 number system. An octal number system consists of eight

single-digit numbers: 0, 1, 2, 3, 4, 5, 6, and 7. the number after 7 is 10. The

number after 17 is 20 and so forth.

In computer programming, the octal equivalent of a binary number is

sometimes used to represent it because it is shorter.

CHARACTERS AND DECIMAL, BINARY, ASCII, CHARACTERS AND DECIMAL, BINARY, ASCII, CHARACTERS AND DECIMAL, BINARY, ASCII, CHARACTERS AND DECIMAL, BINARY, ASCII,

EBCDIC VALUEEBCDIC VALUEEBCDIC VALUEEBCDIC VALUE

Capital Letters

Characters Decimal Binary ASCII EBCDIC

A 65 1000001 1000001 01000001

B 66 1000010 1000010 01000010

C 67 1000011 1000011 01000011

D 68 1000100 1000100 01000100

E 69 1000101 1000101 01000101

F 70 1000110 1000110 01000110

G 71 1000111 1000111 01000111

H 72 1001000 1001000 01001000

I 73 1001001 1001001 01001001

J 74 1001010 1001010 01001010

K 75 1001011 1001011 01001011

L 76 1001100 1001100 01001100

M 77 1001101 1001101 01001101

N 78 1001110 1001110 01001110

O 79 1001111 1001111 01001111

P 80 1010000 1010000 01010000

Q 81 1010001 1010001 01010001

R 82 1010010 1010010 01010010

S 83 1010011 1010011 01010011

T 84 1010100 1010100 01010100

U 85 1010101 1010101 01010101

V 86 1010110 1010110 01010110

W 87 1010111 1010111 01010111

X 88 1011000 1011000 01011000

Y 89 1011001 1011001 01011001

Z 90 1011010 1011010 01011010

CHARACTERS AND DECIMAL, BINARY, ASCII, CHARACTERS AND DECIMAL, BINARY, ASCII, CHARACTERS AND DECIMAL, BINARY, ASCII, CHARACTERS AND DECIMAL, BINARY, ASCII,

EBCDIC VALUEEBCDIC VALUEEBCDIC VALUEEBCDIC VALUE

Small Letters

Characters Decimal Binary ASCII EBCDIC

a 97 1100001 1100001 01100001

b 98 1100010 1100010 01100010

c 99 1100011 1100011 01100011

d 100 1100100 1100100 01100100

e 101 1100101 1100101 01100101

f 102 1100110 1100110 01100110

g 103 1100111 1100111 01100111

h 104 1101000 1101000 01101000

i 105 1101001 1101001 01101001

j 106 1101010 1101010 01101010

k 107 1101011 1101011 01101011

l 108 1101100 1101100 01101100

m 109 1101101 1101101 01101101

n 110 1101110 1101110 01101110

o 111 1101111 1101111 01101111

p 112 1110000 1110000 01110000

q 113 1110001 1110001 01110001

r 114 1110010 1110010 01110010

s 115 1110011 1110011 01110011

t 116 1110100 1110100 01110100

u 117 1110101 1110101 01110101

v 118 1110110 1110110 01110110

w 119 1110111 1110111 01110111

x 120 1111000 1111000 01111000

y 121 1111001 1111001 01111001

z 122 1111010 1111010 01111010

SHORTCUT KEYSSHORTCUT KEYSSHORTCUT KEYSSHORTCUT KEYS

General keyboard shortcuts

Press To ALT+ENTER View properties for the selected item.

ALT+Enter Displays the properties of the selected object.

ALT+ESC Cycle through items in the order they were opened.

ALT+F4 Close the active item, or quit the active program.

ALT+SPACEBAR Opens the shortcut menu for the active window.

ALT+SPACEBAR Display the System menu for the active window.

ALT+TAB Switch between open items.

ALT+Underlined letter in a menu name

Display the corresponding menu.

BACKSPACE View the folder one level up in My Computer or Windows Explorer.

CTRL while dragging an item

Copy selected item.

CTRL+A Select all.

CTRL+C Copy.

CTRL+DOWN ARROW Move the insertion point to the beginning of the next paragraph.

CTRL+ESC Display the Start menu.

CTRL+F4 Close the active document in programs that allow you to have multiple documents open simultaneously.

CTRL+LEFT ARROW Move the insertion point to the beginning of the previous word.

CTRL+RIGHT ARROW Move the insertion point to the beginning of the next word.

CTRL+SHIFT while dragging an item

Create shortcut to selected item.

CTRL+SHIFT with any of the arrow keys

Highlight a block of text.

CTRL+UP ARROW Move the insertion point to the beginning of the previous paragraph.

CTRL+V Paste.

CTRL+X Cut.

CTRL+Z Undo.

DELETE Delete.

ESC Cancel the current task.

F10 Activate the menu bar in the active program.

F2 Rename selected item.

F3 Search for a file or folder.

F4 Display the Address bar list in My Computer or Windows Explorer.

F5 Refresh the active window.

F6 Cycle through screen elements in a window or on the desktop.

LEFT ARROW Open the next menu to the left, or close a submenu.

RIGHT ARROW Open the next menu to the right, or open a submenu.

SHIFT when you insert a CD into the CD-ROM drive

Prevent the CD from automatically playing.

SHIFT with any of the arrow keys

Select more than one item in a window or on the desktop, or select text within a document.

SHIFT+DELETE Delete selected item permanently without placing the item in the Recycle Bin.

SHIFT+F10 Display the shortcut menu for the selected item.

Underlined letter in a command name on an open menu

Carry out the corresponding command.

Dialog box keyboard shortcuts

Press To CTRL+TAB Move forward through tabs.

CTRL+SHIFT+TAB Move backward through tabs.

TAB Move forward through options.

SHIFT+TAB Move backward through options.

ALT+Underlined letter

Carry out the corresponding command or select the corresponding option.

ENTER Carry out the command for the active option or button.

SPACEBAR Select or clear the check box if the active option is a check box.

Arrow keys Select a button if the active option is a group of option buttons.

F1 Display Help.

F4 Display the items in the active list.

BACKSPACE Open a folder one level up if a folder is selected in the Save As or Open dialog box.

Natural keyboard shortcuts You can use the following keyboard shortcuts with a Microsoft Natural Keyboard or any other compatible keyboard that includes the Windows logo

key ( ) and the Application key ( ).

Press To Display or hide the Start menu.

+BREAK Display the System Properties dialog box.

+D Show the desktop.

+M Minimize all windows.

+Shift+M Restores minimized windows.

+E Open My Computer.

+F Search for a file or folder.

CTRL+ +F Search for computers.

+F1 Display Windows Help.

+ L Lock your computer if you are connected to a network domain, or switch users if you are not connected to a network domain.

+R Open the Run dialog box.

Display the shortcut menu for the selected item.

+U Open Utility Manager.

Accessibility keyboard shortcuts

Press To Right SHIFT for eight seconds Switch Filter Keys on and off.

Left ALT +left SHIFT +PRINT SCREEN

Switch High Contrast on and off.

Left ALT +left SHIFT +NUM LOCK

Switch MouseKeys on and off.

SHIFT five times Switch Sticky Keys on and off.

NUM LOCK for five seconds Switch Toggle Keys on and off.

+U Open Utility Manager.

Windows Explorer keyboard shortcuts

Press To END Display the bottom of the active window.

HOME Display the top of the active window.

NUM LOCK+ASTERISK on numeric keypad (*)

Display all subfolders under the selected folder.

NUM LOCK+PLUS SIGN on Display the contents of the selected

numeric keypad (+) folder.

NUM LOCK+MINUS SIGN on numeric keypad (-)

Collapse the selected folder.

LEFT ARROW Collapse current selection if it's expanded or select parent folder.

RIGHT ARROW Display current selection if it's collapsed, or select first subfolder.

WHAT IS DOS?WHAT IS DOS?WHAT IS DOS?WHAT IS DOS?

Microsoft DOS (Disk Operating System) is a command line user

interface. MS-DOS 1.0 was released in 1981 for IBM computers and the latest

version of MS -DOS is MS-DOS 6.22, which was released in 1994. While MS

-DOS is not commonly used by itself today, it still can be accessed from every

version of Microsoft Windows by clicking Start / Run and typing "command"

or by typing "CMD" in Windows NT, Windows 2000 or Windows XP.

Differences between DOS Internal and External

Commands

Internal commands

A command that is stored in the system memory and loaded from the

command.com. Below are examples of internal MS -DOS commands currently

listed in the Computer dos database.

ASSOC BREAK CALL

CD CHDIR CLS

COLOR COPY CTTY

DATE DEL DIR

DRIVPARM ECHO ERASE

EXIT FOR LH

LOADHIGH LOCK MD

MKDIR MOVE PATH

PAUSE PROMPT RD

REN RENAME RMDIR

SET SWITCHES TIME

TYPE

External command

A MS-DOS command that is not included in command.com. External

commands are commonly external either because it requires large requirements

and/or are not commonly used commands. Below are examples of MS-DOS

external commands currently listed in the Computer dos database.

APPEND ARP ASSIGN

AT ATTRIB CACLS

CHCP CHKDSK CHKNTFS

CHOICE COMP COMPACT

CONVERT DEBUG DEFRAG

DELTREE DISKCOMP DISKCOPY

DOSKEY DOSSHELL EDIT

EDLIN EXPAND EXTRACT

FASTHELP FC FDISK

FIND FORMAT GRAFTABL

HELP IPCONFIG LABEL

LOADFIX MEM MODE

MORE MSAV MSCDEX

MSCDEXNT MSD NBTSTAT

NET NETSTAT NLSFUNC

NSLOOKUP PATHPING PING

POWER PRINT ROUTE

SCANDISK SCANREG SETVER

SHARE SHUTDOWN SMARTDRV

SORT SUBST SYS

TRACERT TREE UNDELETE

UNFORMAT

DOS COMMANDS AND EXPLANATIONDOS COMMANDS AND EXPLANATIONDOS COMMANDS AND EXPLANATIONDOS COMMANDS AND EXPLANATION

No Command Name Explanation

01. ASSOC Displays or modifies file extension associations.

02. AT Schedules commands and programs to run on a

computer.

03. ATTRIB Displays or changes file attributes.

04. BREAK Sets or clears extended CTRL+C checking.

05. CACLS Displays or modifies access control lists (ACLs) of

files.

06. CALL Calls one batch program from another.

07. CD Displays the name of or changes the current

directory.

08. CHCP Displays or sets the active code page number.

09. CHDIR Displays the name of or changes the current

directory.

10. CHKDSK Checks a disk and displays a status report.

11. CHKNTFS Displays or modifies the checking of disk at boot

time.

12. CLS Clears the screen.

13. CMD Starts a new instance of the Windows command

interpreter.

14. COLOR Sets the default console foreground and background

colors.

15. COMP Compares the contents of two files or sets of files.

16. COMPACT Displays or alters the compression of files on NTFS

partitions.

17. CONVERT Converts FAT volumes to NTFS. You cannot

convert the current drive.

18. COPY Copies one or more files to another location.

19. DATE Displays or sets the date.

20. DEL Deletes one or more files.

21. DIR Displays a list of files and subdirectories in a

directory.

22. DISKCOMP Compares the contents of two floppy disks.

23. DISKCOPY Copies the contents of one floppy disk to another.

24. DOSKEY Edits command lines, recalls Windows commands,

and creates macros.

25. ECHO Displays messages, or turns command echoing on or

off.

26. ENDLOCAL Ends localization of environment changes in a batch

file.

27. ERASE Deletes one or more files.

28. EXIT Quits the CMD.EXE program (command

interpreter).

29. FC Compares two files or sets of files, and displays the

differences between them.

30. FIND Searches for a text string in a file or files.

31. FINDSTR Searches for strings in files.

32. FOR Runs a specified command for each file in a set of

files.

33. FORMAT Formats a disk for use with Windows.

34. FTYPE Displays or modifies file types used in file extension

associations.

35. GOTO Directs the Windows command interpreter to a

labeled line in a batch program.

36. GRAFTABL Enables Windows to display an extended character

set in graphics mode.

37. HELP Provides Help information for Windows commands.

38. IF Performs conditional processing in batch programs.

39. LABEL Creates, changes, or deletes the volume label of a

disk.

40. MD Creates a directory.

41. MKDIR Creates a directory.

42. MODE Configures a system device.

43. MORE Displays output one screen at a time.

44. MOVE Moves one or more files from one directory to

another directory.

45. PATH Displays or sets a search path for executable files.

46. PAUSE Suspends processing of a batch file and displays a

message.

47. POPD Restores the previous value of the current directory

saved by PUSHD.

48. PRINT Prints a text file.

49. PROMPT Changes the Windows command prompt.

50. PUSHD Saves the current directory then changes it.

51. RD Removes a directory.

52. RECOVER Recovers readable information from a bad or

defective disk.

53. REM Records comments (remarks) in batch files or

CONFIG.SYS.

54. REN Renames a file or files.

55. RENAME Renames a file or files.

56. REPLACE Replaces files.

57. RMDIR Removes a directory.

58. SET Displays, sets, or removes Windows environment

variables.

59. SETLOCAL Begins localization of environment changes in a

batch file.

60. SHIFT Shifts the position of replaceable parameters in

batch files.

61. SORT Sorts input.

62. START Starts a separate window to run a specified program

or command.

63. SUBST Associates a path with a drive letter.

64. TIME Displays or sets the system time.

65. TITLE Sets the window title for a CMD.EXE session.

66. TREE Graphically displays the directory structure of a

drive or path.

67. TYPE Displays the contents of a text file.

68. VER Displays the Windows version.

69. VERIFY Tells Windows whether to verify that your files are

written correctly to a disk.

70. VOL Displays a disk volume label and serial number.

71. XCOPY Copies files and directory trees.

MODEM ERROR MESSAGESMODEM ERROR MESSAGESMODEM ERROR MESSAGESMODEM ERROR MESSAGES

No Error Messages

600 An operation is pending.

601 An invalid port handle was detected.

602 The specified port is already open.

603 The caller's buffer is too small.

604 Incorrect information was specified.

605 The port information cannot be set.

606 The specified port is not connected.

607 An invalid event is detected.

608 A device was specified that does not exist.

609 The device type was specified that does not exist.

610 An invalid buffer was specified.

611 A route was specified that is not available.

612 A route was specified that is not allocated.

613 An invalid compression was specified.

614 There were insufficient buffers available.

615 The specified port was not found.

616 An asynchronous request is pending.

617 The modem is already disconnecting.

618 The specified port is not open.

619 The specified port is not connected.

620 No endpoints could be determined.

621 The system could not open the phonebook.

622 The system could not load the phonebook.

623 The system could not find the phonebook entry for this connection.

624 The system could not update the phonebook file.

No Error Messages

625 The system found invalid information in the phonebook.

626 A string could not be loaded.

627 A key could not be found.

628 The connection was closed.

629 The connection was closed by the remote computer.

630 The modem was disconnected due to hardware failure.

631 The user disconnected the modem.

632 An incorrect structure size was detected.

633 The modem is already in use or is not configured for dialing out.

634 Your computer could not be registered on the remote network.

635 There was an unknown error.

636 The device attached to the port is not the one expected.

637 A string was detected that could not be converted.

638 The request has timed out.

639 No asynchronous net is available.

640 An error has occurred involving NetBIOS.

641 The server cannot allocate NetBIOS resources needed to support the

client.

642 One of your computer's NetBIOS names is already registered on the

remote network.

643 A network adapter at the server failed.

644 You will not receive network message popups.

645 There was an internal authentication error.

646 The account is not permitted to log on at this time of day.

647 The account is disabled.

648 The password for this account has expired.

649 The account does not have permission to dial in.

650 The remote access server is not responding.

651 The modem has reported an error.

No Error Messages

652 There was an unrecognized response from the modem.

653 A macro required by the modem was not found in the device .INF file

section.

654 A command or response in the device .INF file section refers to an

undefined macro.

655 The <MESSAGE> macro was not found in the device .INF file section.

656 The <DEFAULTOFF> macro in the device .INF file section contains an undefined macro.

657 The device .INF file could not be opened.

658 The device name in the device .INF or media .INI file is too long.

659 The media .INI file refers to an unknown device name.

660 The device .INF file contains no responses for the command.

661 The device .INF file is missing a command.

662 There was an attempt to set a macro not listed in the device .INF file

section.

663 The media .INI file refers to an unknown device type.

664 The system has run out of memory.

665 The modem is not properly configured.

666 The modem is not functioning.

667 The system was unable to read the media .INI file.

668 The connection was terminated.

669 The usage parameter in the media .INI file is invalid.

670 The system was unable to read the section name from the media .INI

file.

671 The system was unable to read the device type from the media .INI file.

672 The system was unable to read the device name from the media .INI file.

673 The system was unable to read the usage from the media .INI file.

674 The system was unable to read the maximum connection BPS rate from

the media .INI file.

No Error Messages

675 The system was unable to read the maximum carrier connection speed

from the media .INI file.

676 The phone line is busy.

677 A person answered instead of a modem.

678 There was no answer.

679 The system could not detect the carrier.

680 There was no dial tone.

681 The modem reported a general error.

691 Access was denied because the user name and/or password was invalid

on the domain.

692 There was a hardware failure in the modem.

695 The state machines are not started.

696 The state machines are already started.

697 The response looping did not complete.

699 The modem response caused a buffer overflow.

700 The expanded command in the device .INF file is too long.

701 The modem moved to a connection speed not supported by the COM

driver.

703 The connection needs information from you, but the application does not

allow user interaction.

704 The callback number is invalid.

705 The authorization state is invalid.

707 There was an error related to the X.25 protocol.

708 The account has expired.

709 There was an error changing the password on the domain. The password

might have been too short or might have matched a previously used

password.

710 Serial overrun errors were detected while communicating with the

modem.

No Error Messages

711 The Remote Access Service Manager could not start. Additional

information is provided in the event log.

712 The two-way port is initializing. Wait a few seconds and redial.

713 No active ISDN lines are available.

714 No ISDN channels are available to make the call.

715 Too many errors occurred because of poor phone line quality.

716 The remote access service IP configuration is unusable.

717 No IP addresses are available in the static pool of remote access service

IP addresses.

718 The connection timed out waiting for a valid response from the remote

computer.

719 The connection was terminated by the remote computer.

721 The remote computer is not responding.

722 Invalid data was received from the remote computer. This data was

ignored.

723 The phone number, including prefix and suffix, is too long.

726 The IPX protocol cannot be used for dial-out on more than one modem

at a time.

728 The system cannot find an IP adapter.

729 SLIP cannot be used unless the IP protocol is installed.

731 The protocol is not configured.

732 Your computer and the remote computer could not agree on PPP control

protocols.

733 Your computer and the remote computer could not agree on PPP control

protocols.

734 The PPP link control protocol was terminated.

735 The requested address was rejected by the server.

736 The remote computer terminated the control protocol.

737 Loop back detected.

No Error Messages

738 The server did not assign an address.

739 The authentication protocol required by the remote server cannot use the

stored password. Redial, entering the password explicitly.

740 An invalid dialing rule was detected.

741 The local computer does not support the required data encryption type.

742 The remote computer does not support the required data encryption type.

743 The remote server requires data encryption.

751 The callback number contains an invalid character. Only the following

characters are allowed: 0 to 9, T, P, W, (,), -, @, and space.

752 A syntax error was encountered while processing a script.

753 The connection could not be disconnected because it was created by the

multi-protocol router.

754 The system could not find the multi-link bundle.

755 The system cannot perform automated dial because this entry has a

custom dialer specified.

756 This connection is already being dialed.

757 Remote access services could not be started automatically. Additional

information is provided in the event log.

758 Internet Connection Sharing is already enabled on the connection.

760 An error occurred while routing capabilities were being enabled.

761 An error occurred while Internet Connection Sharing was being enabled

for the connection.

763 Internet Connection Sharing cannot be enabled. There are two or more

LAN connections in addition to the connection to be shared.

764 No smart card reader is installed.

765 Internet Connection Sharing cannot be enabled. A LAN connection is

already configured with the IP address required for automatic IP

addressing.

No Error Messages

767 Internet Connection Sharing cannot be enabled. The LAN connection

selected on the private network has more than one IP address configured.

Reconfigure the LAN connection with a single IP address before

enabling Internet Connection Sharing.

768 The connection attempt failed because of failure to encrypt data.

769 The specified destination is not reachable.

770 The remote machine rejected the connection attempt.

771 The connection attempt failed because the network is busy.

772 The remote computer's network hardware is incompatible with the type

of call requested.

773 The connection attempt failed because the destination number has

changed.

774 The connection attempt failed because of a temporary failure. Try

connecting again.

775 The call was blocked by the remote computer.

776 The call could not be connected because the destination has invoked the

Do Not Disturb feature.

777 The connection attempt failed because the modem on the remote

computer is out of order.

778 It was not possible to verify the identity of the server.

780 An attempted function is not valid for this connection.

783 Internet Connection Sharing cannot be enabled. The LAN connection

selected as the private network is either not present, or is disconnected

from the network. Please ensure that the LAN adapter is connected

before enabling Internet Connection Sharing.

784 You cannot dial using this connection at logon time, because it is

configured to use a user name different than the one on the smart card. If

you want to use it at logon time, you must configure it to use the user

name on the smart card.

No Error Messages

785 You cannot dial using this connection at logon time, because it is not

configured to use a smart card. If you want to use it at logon time, you

must edit the properties of this connection so that it uses a smart card.

788 The L2TP connection attempt failed because the security layer could not

negotiate compatible parameters with the remote computer.

789 The L2TP connection attempt failed because the security layer

encountered a processing error during initial negotiations with the

remote computer.

791 The L2TP connection attempt failed because security policy for the

connection was not found.

792 The L2TP connection attempt failed because security negotiation timed

out.

793 The L2TP connection attempt failed because an error occurred while

negotiating security.

794 The Framed Protocol RADIUS attribute for this user is not PPP.

795 The Tunnel Type RADIUS attribute for this user is not correct.

796 The Service Type RADIUS attribute for this user is neither Framed nor

Callback Framed.

797 A connection to the remote computer could not be established because

the modem was not found or was busy.

799 Internet Connection Sharing (ICS) cannot be enabled due to an IP

address conflict on the network. ICS requires the host be configured to

use 192.168.0.1. Please ensure that no other client on the network is

configured to use 192.168.0.1.

800 Unable to establish the VPN connection. The VPN server may be

unreachable, or security parameters may not be configured properly for

this connection.

ABBREVIATIONABBREVIATIONABBREVIATIONABBREVIATION

01. A/L Alphanumeric

02. ABC Atanasoft Berry Computer

03. ACE Automatic Computing Engine

04. ACK Acknowledgement

05. ADC Analog to Digital Converter

06. ADSL Asynchronous Digital Subscriber Loop

07. AI Artificial Intelligence

08. ALGOL Algorithmic language

09. ALU Arithmetic and Logic Unit

10. ANSI American National Standards Institution

11. AOL America On Line

12. APL A Programming Language

13. ARPANET Advanced Research Project

14. AS Auxiliary Storage

15. ASCC Automatic Sequence – Controlled Calculator

16. ASCII American Standard Cord for Information Interchange

17. ATM Automatic Teller Machines

18. ATM Asynchronous Transfer Mode

19. BA Binary Address

20. BASIC Beginner’s All-Purpose Symbolic Instruction Code

21. BC Binary Code

22. BCD Binary Coded Decimal

23. BCDIC Binary Coded Decimal Interchange Code

24. BCO Binary Coded Octal

25. BIS Business Information System

26. BIT Binary Digit

27. BPS Bit Transaction Processing

28. BPS Bits Per Second

29. CAD Computer Aided Design

30. CAE Computer Aided Engineering

31. CAI Computer Aided Instruction

32. CALS Computer Aided Logistic and Support

33. CAM Computer Aided Manufacturing

34. CAM Computer Assisted Manufacture

35. CAR Computer Assisted Retrieval

36. CASE Computer Aided Software Engineering

37. CBASIC A Complier Vision Of BASIC

38. CCITT Consultative Committee For International Telephony

And Telegraphy

39. CCTTT Acronym For International Committee or Telephone

And Telegraphy

40. CCU Central Control Unit

41. CD Compact Disk

42. CDE Channel Definition Format

43. CDMA Common Division Multiple Access

44. CD-ROM Compact Disk-Read Only Memory

45. CERN Center For European Nuclear Research

46. CGA Color Graphic Adaptor

47. CGI Computer Galway Interface

48. CGI Computer Galway Interface

49. CHS Character per Second

50. CIM Computer Input on Microfilm

51. CIM Chief Information Officer

52. CIP Current Instruction Register

53. CISC Complex Instruction Set Computer

54. CIU Computer Interface Unit

55. CMOS Complimentary Metal Oxide Semiconductor

56. COBOL Common Business Oriented Language

57. CODASYL Conference For Data Systems Language

58. CODEC Coder /Decoder

59. COL Computer Oriented Language

60. COM Computer Output on Microfilm

61. CPS Character Per Second / Cycles Per Second

62. CPU Control Processing Unit

63. CR Character Recognition

64. CRT Cathode Ray Tube

65. CSCW Computer Supported Co-operative Work

66. CSMACD Carrier Sense Multiple Access With Collision Detector

67. CU Control Unit

68. CUI Character User Interface

69. CVT Constraint Voltage Transformer

70. DAC Digital To Analog Converter

71. DBA Data Base Administrator

72. DBMS Data Base Management System

73. DDL Data Descript n Language

74. DDRAM Dynamic Densities Random Access Memory

75. DDRRAM Dynamic Densities Routine Access Memory

76. DEC Digital Equipment Corporation

77. DEM Data Management System

78. DIMM Double Inline Memory Module

79. DML Data manipulation Language

80. DMP Dot Matrix Printer

81. DNS Domain Name Server

82. DOI Dots Pen Inch

83. DRAM Dynamic Random Access Memory

84. DSP Digital Signal Processing

85. DTP Desk –Top Publishing

86. DVD Digital Video Interface

87. EAN European Article Number

88. EBCDIC Extended Binary Coder Decimal Interchange Code

89. EDI Electronic Data Interchange

90. EDSAC Electronic Delay Storage Automatic Calculator

91. EDVAC Electronic Discrete Vary Able Automatic Computer

92. EFT Electronic Funds Transfer

93. EGA Enhanced Graphics Adaptor

94. EL Electro Luminescent

95. EM Electronic Mail

96. EMACS Extended Industry Standard Architecture

97. EMAIL Electronic Mail

98. ENIAC Electronic Numerical Integrator And Calculator

99. EOF End Of File

100. EOT End Of Transmission

101. ERP Enterprise Requirements Planning

102. FAQ Frequently Asked Question

103. FDC Floppy Disk Controller

104. FDDI Fiber Distributed Data Interchange

105. FGL Fourth Generation Language

106. FORTRAN Formula Translation

107. FTP File Transfer Protocol

108. GB Gigabyte

109. GIF Graphical Interchange Format

110. GIGO Garbage In Garbage Out

111. GNU Guns Not Unix

112. GPC General Purpose Computer

113. GPIB General Purpose Interface Bus

114. GPSS General Purpose Systems Simulator

115. GPSS Global Positioning System

116. GSM Global System for Mobile

117. GUS Graphical User Interface

118. HDML Hyper Device Markup Language

119. HLL High Level Language

120. HSP High Speed Printer

121. HTML Hyper Text Markup Language

122. HTTP Hyper Text Transfer Protocol

123. I/O Input/Output

124. IBM International Business Machines

125. IBM-PC IBM Personal Computer

126. IC Integrated Circuits

127. ID User Identification

128. IETF International Engineering Task Force

129. IOD Input/output Device

130. IOR Instruction Register

131. IP Information Provider

132. IP Internet Protocol

133. ISA Industry Standard Architecture

134. ISDN Integrated Service Digital Network

135. ISO International Standards Organization

136. ISP Internet Service Provider

137. ISR Information Storage and Retrieval

138. IU Input Unite

139. JANET Joint Academic Network

140. JCL Joy Control Language

141. JPEG Joint Photography Experts Group

142. K Kilo

143. KB Kilo Byte(1024)

144. LAN Local Area Network

145. LASER Light Amplification by the Stimulated Emission of

Rendition

146. LCD Liquid Crystal Display

147. LCS Liquid Crystals Shutter

148. LDAP Lightweight Directory Access Protocol

149. LED Light Emitting Diode

150. LIFO Last In First Out

151. LISP List Processing Language

152. LISP List Processor

153. LPM Line per Minute

154. LPS Line per Second

155. LPS Line per Minute

156. LQP Letter Quality Printer

157. LSB Least Significant Bit

158. LSD Least Significant Digit

159. LST Large Scale Integration

160. MAE Metropolitan Area Ethernet

161. MAP Manufacturing Automation Portal

162. MAR Memory Address Register

163. MB Megabyte

164. MBR Memory Buffer Register

165. MDAS Medicate Data Acquisition System

166. MF Master File

167. MIDI Musical Instrument Digital Interface

168. MIME Multipurpose Internet Mailing Extensions

169. MIPS Million Instruction Per Second

170. MIS Management Information System

171. ML Marching Processing Language

172. MODEM Modulator Demodulator

173. MOO Mud Object Oriented

174. MOS Metal Oxide Semi Conductors

175. MPEG Moving Pictures Experts Group

176. MR Memory Register

177. MR Modem Ready

178. MSB Most Significant Bit

179. MSD Most Significant Digit

180. MS-DOS Micro Soft Disk Operating System

181. MSI Medium Scale Integration

182. MSN Micro Soft Network

183. MT Magnetic Tape

184. NLQ Near Letter Quality

185. NMF New Master File

186. NREN National Research And Education Network

187. NSFNET National Science Foundation Network

188. NTFS Non Transfer File System

189. OCR Optical Character Reader /Recognition

190. OH Off Hook

191. OLE Object Linking Embedding

192. OLTP Online Transaction Processing

193. OMF Old Master File

194. OMR Optical Mark Recognition Reading

195. OPCODE Operation Code

196. OPP Object Oriented Programming

197. OS/2 Operating System/2

198. PBX Private Branch Exchanges

199. PC Program Counter (Also Personal Computer)

200. PIO Processor Input/Output

201. PL Programming Language

202. POS Point-Of Sale

203. PPM Page Per Minute

204. PPP Point-To Point Protocol

205. PROM Programmable Read Only Memory

206. PSM Personal Identification No

207. PSTN Public Switch Telephone Network

208. RAMAC Random Access Method for Accounting and Control

209. RD Receive Data

210. RF Radio-Frequency

211. RGB Red Green Blue

212. RISC Reduced Instruction –Set Computer

213. RJE Remote Job Entry

214. ROMBIOUS Read Only Memory Basic Input Output System

215. RPG Report Program Generator

216. RS-232 Regular Standard No 232

217. SAGE Semi Automatic Ground Environment

218. SDRAM Single Dynamic Random Access Memory

219. SGML Standard Generalized Markup Language

220. SIMM Single Inline Memory Module

221. SLIP Serial Line Internet Protocol

222. SLT Solid Logic Technology

223. SNOBOL String Oriented Symbolic Language

224. SOH Start of Heading

225. SRAM Single Random Access Memory

226. S-SEED Symmetric Self-Electro-Optic-Effect-Devices

227. SSL Secure Sockets Layer

228. SVGA Super Video Graphic Adaptor

229. TCP Transmission Control Protocol

230. TD Transmitted Data

231. TELEX Teleprinter Exchange

232. TP Transaction Processing

233. TRADIC Transistorized Airborne Digital Computer

234. UIS Universal Information Server

235. UNIVAC Universal Automatic Computer

236. UPC Universal Product Code

237. UPS Uninterrupted Power Supply

238. URL Uniform Resource Locater

239. USB Universal Serial Bus

240. UT User Terminal

241. VCD Visual Display Unit

242. VDU Visual Display Unit

243. VGA Video Graphic Adaptor

244. VM Virtual Memory

245. VRS Voice Recognize System

246. VS Virtual Storage

247. WAN Wide-Area Network

248. WORM Write Once Read Many

249. WP Word Processing

250. WWW World Wide Web