git sg chapter 1

8/3/2019 GIT SG Chapter 1

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1 Introduction to Information Technology

1.1 Introduction to Information Technology (IT)

1.1.1 Usage and Importance of IT

There is a general belief that Information

Te chno logy ( IT) i s abou t com pute r s . H ow ever ,

this is not true. Information Technology (IT) is

about computers , communicat ion networks , and

pe ople sharing information and knowled ge

utilizing such computers and communication

networks. Information Technology (IT) has

enabled people in different parts of the world to

exchange informat ion f re e ly and with e as e . In

effect , IT make s us re alize how s mall the wor ld,

we l ive in , is as i t removes physical const ra ints

such as d is tance between people in exchanging

information.

With rapid de velopments in IT, globa l commu nicat ion took a gia nt le ap . Toda y,

Information Technology (IT) is practically utilized in diverse fields such as education,

scienc e, e ngineering and te chnology, manufacturing, banking, air l ine industr y, health

and medic ine , provis ion of public and other se rvices , c ommerce , adminis t ra t ion andmanagement e tc . We a l l have bec ome use rs of many of these IT a ppl ica t ions in our

day- to- day l ives , no matter how sophist icated or modera te our lifes tyles are .

Fur ther , more and more IT appl ica t ions are int roduced to human act iv it ies and wi th

this sc ena r io i t is surmise d that , in fu ture , knowledge in IT wi l l be an es s e nt ia l

requi rement for a pers on to se cure a ny form of employment or eve n par t ic ipate as a

member of the modern day society.

In fo rma tio n T e c hn olo gy ( IT ) h a s o p e n e d u p a w h o l e n e w r a n g e o f e m p l o y m e n t

oppor tuni t ies as programmers , sys tems analys ts , sys tems des igners , sof tware

enginee rs , sof tware archi tec ts , sys tems e ngineers , da tabase adminis t ra tors , ne twork

engineers, network administrators, computer hardware professionals, Website

deve lopers , mult imedia profe ss ionals, IT co nsultants and the l ike. In addit ion, IT has

c re a t e d vas t job oppor tun it i e s i n o the r f ie lds such a s m anagem ent , accoun tancy ,

commerce, banking, publishing and media, engineering, architecture, health and

medicine.


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There are a lso emerging areas of specia l iza t ion such as e lec t ronic commerce , Web

services , ne twork and data secur i ty , in te l l igent sys tems, e-government services a l l

spurred by IT.

With the a vailabili ty of a wide variety of employment opportunit ies in the f ield of IT

and a whole ho st of oppor tunit ies in the f ield of IT a pplications in othe r disciplines ,

those who are knowledgeable and proficient in IT will naturally f ind satisfying jobs

w ith h igh r e m unera t ion bo th he re and ab road . Th i s i s good e nough r eas on fo r any

student to embark on s tudies in IT.

1.1.2 Some Common IT Applications

Information T ec hnolog y (IT) has found i ts way

into more and more as pects of our soc ie ty . Be i t

a s upermarke t , a hos pital , a teac hing inst i tut ion, a

bank or even the household, there are s ys tems or

products that depend on IT or utilize IT.

L e t u s t a k e t h e e x a m p l e o f a mo d e r n h o s p i t a l.

When you visit such a hospital, you will be able to

se e se vera l appl ica t ions of IT. I f you want to get

an appointment with a specialist doctor, the

receptionist at the appointment desk will

invar iably input some data v ia the keyboar d of a

computer to the hos pitals information sys tem and within se conds, s he will be able toinform you of the availability of that particular doctor on a given date, at a given time,

a t a spe c i fi ed locat ion. She i s us ing the m ana ge m en t in fo rma t ion s ys t e m of t he

hospital to give y ou fast a nd accurate information.

If you get a chance to visi t an Intensive Care Unit (ICU) of a hospital , you will f ind

much more significant IT applications s uch as monitoring of blood circulat ing sys tem,

cardiographs monitoring heart beat, encephalographs monitoring brain functions.

The se sys tems handle cr i t ica l informat ion about the pat ient s condit ion which he lps

the doctor to give the patient t imely and bette r tre atment.

N ex t cons ide r a s choo l . Even a t a s choo l, s tuden t i n fo rm a t ion such a s nam e o f t he

s tudent , re gis t ra t ion number , s tude nt s addres s , s tude nt s examinat ion mark s and

performance, and informat ion about the s tude nt s e xt ra - curr icular ac t iv i t ies can be

kept in a s tudent information syste m. Students, te acher s, principal and parents wil l be

able to access this information. Such information systems help in the better

management of the s chool.


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Now you w il l unde r s t and tha t t he w o r ld is ge t t i ng

u s e d t o m o r e a n d m o r e IT a p p li c a t io n s o n a g l o ba l

scale. This is why we say that the world is globalis ed.

This is not only because IT on i ts own proved a great

succes s bu t a lso because IT g re w to be an e s se n t ia l

tool tha t fac i li ta tes a nd enhance s ac t iv i t ies in most

other f ields.

1.1.3 Why Study IT?

Every one has an am bit ion to becom e a

succe ss ful pers on in society. You may be

planning to become an accountant , a

doctor, an engineer, a lecturer, an IT

professional or a business man. No

m at t e r w ha t your p lans a re , s tudy ing IT

upto an appropriate level will be a

decisive advantage and will certainly

help you to prospe r in your care er.

Let us take a case where a s tudent choose s the medical profes s ion. Being a doctor is

to belong to a noble profess ion. I t i s a job that requi res a great deal of knowledge

about the human s ys te m. But a t the s ame t ime , be ing compete nt in Information

Te chnology wil l provide an addi t ional competence to a doctor in the pract ice of h is

p ro fes s ion . For exam ple , a s a doc to r , one m ight f ace a s i t ua t ion w here one has to

use a so phist icated me dical equipment to obtain an electr ocardiograph of a patient or

you may use a moder n Magnetic Resonance Imaging (MRI) scanne r to sca n the human

body. If the doc tor has so me knowledge in Information Te chnology it will help him to

handle these equipment confidently and effectively.

On the other hand one might prefer to be come an acade mic , such as a lec ture r or a

r e s ea rc he r . Today academ ics ge t inva luab le he lp from IT in the p rac t i ce o f t he i r

profes s ion, be it for captur ing, proce ss ing or analys is of informat ion, prese nta t ion,

transmission of information to distant audience s or conduct of IT base d ex aminations

and evaluation. Academics depend heavily on Internet, specialized application

software a nd they deve lop the ir ow n so f tw ar e in the co ndu c t o f r e sea rch an d

d i s se m ina t ion o f know ledge . Thus i t is s ee n tha t an ac adem ic canno t be d ivorced

from IT.


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If o n e i s p l a n n in g t o b e a n I T p r o f e s s i o n a l , n a t u r a l ly o n e h a s t o a c q u i r e a h i g h

proficiency in IT, well beyond the IT knowledge required by othe r profes sionals. One

popu la r a r e a o f IT indus t ry i s so f tw are . Sof tware indus t ry has becom e e x t r e m ely

p o p u la r i n m o d e r n t i me s a n d i t h a s g e n e r a t e d a l a r g e n u m b e r o f j o b s i n v a r io u s

ca tegor i e s bo th in the de ve loped and the deve loping w or ld. There a re a va r i e ty o f

ca ree r s i n so f tw are indus t ry such a s so f tw are eng inee r s , so f tw are t e s t eng inee r s ,

sys t em s ana lys t s , so f tw are deve lope r s , so f tw are p ro jec t m anager s , e t c w hich a re

h ighly r em unera t ive . T o en te r s uch f ie lds o f em ploym ent , one nee ds to be h igh ly

knowledgeable and proficient in IT.

If a s tudent wants to purs ue a care er as a te lecommunicat ion engineer , it w i ll not be

poss ible for h im to proce ed wi thout a s t r ong component of IT in h is s tudies . T oday,

te lecommunicat ions and IT go hand - in- hand and one disc ipline depends on the other

for advancement . In developed countr ies , landlines , wire les s a nd mobile phones are

used extensively and even in Sri Lanka, over the last few years, telecom industry has

shown t remendous progre ss and employment prospects in th is indust ry have be come

pretty at trac tive. To s ecure employme nt in this s ector , one has to be highly proficient

in IT and Communication Technologies.

For that mat ter , a l l engineer ing and s c ience

b a s e d p r o f e s s i o n s r e q u i r e s t u d i e s i n IT a s

engineer ing or scientific analysis and de sign

cannot be performed without resort ing to IT.

Further, accountancy, management, banking,

insura nce e tc . re ly heavi ly on IT e spe cia llywhen dealing with large cl ient- bas e.

The above examples c lear ly demonst ra te

the importance of IT in most areas of

employment and s tudents must prepare

themselves for the challenges of these

pro fes s ions by acqu ir ing the neces sa ry IT

knowledge and proficiency beginning at

school level.

Studying IT is both challenging and interest ing. The rest of this chapter provides the

stude nt, information on data , data pr oce ss ing, information, history of co mpu te rs ,

microprocessor development, computer organization and architecture, storage

devices, peripherals, software, data communication, computer networks, Internet and

the World Wide Web.


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1.1.4 Data and Information

Let us as sume that y ou have completed your Advanced Level ex aminat ion and have

n o w g o t t o k n o w y o u r r e s u lt s . N o t o n ly y o u r p a r e n t s , e v e n f r i e n d s , t e a c h e r s a n d

relat ives a re ver y curious to know your res ults . When someone as ks for your results ,

you m ay sa y tha t i t is 2 A s and a B . Your ans w er m ay no t be e nough to che ck

w h e t h e r y o u c a n e n t e r a u n iv e r s i ty . T h e y m i g h t a s k a b o u t y o u r Z- s c o r e a n d t h e

distr ict rank etc. T hat shows that the f irst ans wer did not contain enough information

to make a judgment . If your answer t o the f ir s t que s t ion is only the marks tha t you

obtained for the subjects if those are available, wil l they ha ve a ny meaning? Probably

not, and no judgment can be made using raw marks.

Thes e r aw marks that ar e most probably not adequate to make a judgment are ca l led

Data . The se raw marks should be conver ted in to more usable and meaningful form.This tas k i s done by the Depar tment of Examinat ions . I t collec ts mar ks for s ubjects

that a s tudent has score d a t the examinat ion and t ra nsform them into dif fere nt forms

which become informat ion for another pers on. There fore , da ta should be proce ss ed

or tra nsformed into a differe nt form to become information as in depicted Figure 1.1.

This t ransformat ion or in terpre ta t ion can be done throug h computer s . Now we can

formally define Data and Information.

Figure 1.1 Processing and conversion of data in to information.

CLASS ACTIVITIES 1 . 1

1. Search through several news papers, for recent articles that discuss the use of

Information technology in society and collect some articles on different IT

applications available presently and categorize them. Summarize some informationabout Computer Assisted Learning (CAL) in schools.

2. Develop a list of occupations that can benefit from using Information Technology.

Keep this list and refer back to it at the end of the course. Then revise the list in

the light of what you have learned, coming up with examples of how to apply

Information Technology.

Processing /ConversionDataInformation


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Data:

Data is a representation of a fact , number, word, image, or sound such as t ime, date,

prices , name, numbers of items sold e tc.

Information:In fo rm a t ion i s p roces se d da t a t ha t i s m ea n ingfu l o r use fu l t o som e one s uch a s Z-

scor e of Advanced leve l examinat ion re sul t s , Salary s l ip of an e mployee , evaluat ion

repor t of a s tudent e tc .

1.1.5 Computers for Data Processing

Now we under stand t he importance of transforming data into useful information. This

process is called Data Processing. Input to a data processing system will be raw data

and the output wi ll be the re quire d informat ion or proces se d data . Who can do th is

transformation or proc es sing? Can a human do this or do we nee d a machine? Look at

our previous example of process ing of AL examinat ion resul t s . The Depar tment of

Exam ina t ions may p roces s t he r e s u lt s o f abou t 200 ,000 AL s tuden t s a ye a r . The

process ing o f AL exam ina t ion r e s u lt s can be ex t r em ely t im e consum ing o r eve n

imposs ible without the a id of a computer . T he computer helps us by proc es s ing the

data given and providing re sults or re ports that contain spe cific information for us to

analyze or understand. Th is information can he lp you reach a de cision.

B ut t he com pute r canno t t ake de c i s ions to p roces s da t a by i t s e l f a s a hum an does

when analyzing and processing data. A human should accurately give instructions or

steps that are needed for a computer to work. Computer follows specific instructions

step by step and needs accurate instructions and data to work with. Machines have to

do th ings the ha r d w ay . U nlike hum ans , t he com pute r s do one th ing a t a t ime , one

s te p a t a t ime. Al l complex procedure s must be broken down into very s imple s teps .

If you use a computer to add two numbers , instructions s hould be given in steps as:

Then these s teps can be repeate d hundreds or thousands or mi ll ions of t imes without

m ak ing e r ro r s . If t he ins t ruc t ions a re accura t e ly g iven to the c om pute r , accura t e

r e s u lt s c a n b e o b t a i n e d . Bu t h u ma n s m a y m a k e m is t a k e s w h e n t h e y r e p e a t t he

process s evera l t imes .

Input Number 1

Input Number 2

addition = Number 1 + Number 2

Output addition


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1.1.6 Characteristics of Information

What we understood was that the information is processed data which can be used to

make a decision. Now we will t ry to discover the quali t ies that make information so

handy. The main qualities that information should have are given below:

Timeliness: It should be available at the corre ct t ime.

Completeness: It should be sufficient for the purpose.

Accuracy: It should be correct and reliable.

Understandability: It s hould be clear in mea ning, prac tical and simple.

1.2 Introduction to Computers

1.2.1 Computer Hardware

Rec a l l a p i c tu re o f a com pute r yo u have s ee n . Wha t doe s i t l ook l ike? H ave you

n o t ic e d i t h a s m o r e t h a n o n e p a r t ? Al l t h e s e d e v ic e s a r e c a l le d h a r d w a r e o f t h e

computer. In other words those are the tangible things that make up a computer.

1

43

2

1. Display Unit2. System Unit

3. Keyboard

4. Mouse


1. Write some notes to explain how computers can be used for data processing.

2. Identify some other places where computers are used for data processing. Preparea list of them and describe few data processing activities.

3. Observe student registration activities of a school. If the information of studentsare going to be kept in a Student Information System (SIS), identify the following

components:

Inputs to the systemProcesses of the system

Outputs of the system


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As the above picture shows , a computer will typically consist of a se t of devices. T he

most significant ones are Display, System Unit, Keyboard and Mouse. System Unit is

t h e p l a c e w h e r e t h e b r a i n o f t h e c o m p ut e r e x i s t s . B y it s e l f c o m p u t e r h a s n o

intel ligence and is re ferred to a s hardware, which me ans s imply the phys ical

equipment . A com pute r w i l l no t be us e fu l w ithou t m ak ing a com pute r s ys t e m . A

computer s yste m is a combination of six elements :

1. Hardware basic electronic and electro - mechanical parts in a computer

2. Software instruction to har dware

3. Data and Info rmation data as input and information as proce ss ed dat a

4. Proce dures or instructions guidelines to use s oftware and hardware

5. People Those Operating the computer system

6. Communication connection betwee n computers to s hare data a nd information

Now we will look at the main components of computer har dware . Gene rally computer

hardware can be divided in to five ca tegor ies : (1) input devices , (2) proces sor s , (3)

storage devices, (4) output devices, a nd (5) communications.

1.2.1.1 Input devices

In pu t d e v ic e s a r e u s e d t o i n pu t d a t a t h a t i s t o b e p r o c e s s e d a n d p r o g r a m s t h a t

inc ludes p rocess ing ins t ruc t ions to the com pute r . Com m on inpu t dev ice s a r e t he

keyboard and the m ouse . There a re o the r i npu t dev ices such a s po in t ing dev ices ,

sca nning devices, smart car ds and optical cards, sensor s, digital cameras etc.

Keyboard:In a c o m p ut e r , a k e yb oa r d c o n v e r t s l e t t e r s , n u m b e r s a n d o t h e r c h a r a c t e r s i n t o

electrical signals that are computer readable. The keyboard may look like a

typewriter keyboard to which some spe cia l keys have bee n added such as Inser t key,

Enter ke y, Home ke y, Ctrl key, Alt key, e tc.

Computer Keyboard


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Pointing devices:

P o i n t in g d e v i c e s u s e o n e o f t h e m o s t n a t u r a l g e s t u r e s o f h u m a n s i. e . t h e a c t o f

pointing. Mouse , trackballs , joysticks, touch scree ns are some of the most frequently

used pointing devices.

Mouse

Mouse is a pointing device. A ball underneath

ro l ls a s t he m ouse m oves ac ros s t he m ouse pad .

The cu r so r on the sc reen fo l low s the m ovem ent

of the mouse. Buttons on the mouse can be

clicked or double - clicked to per form tasks , like to

select an icon on the screen or to open the

selec ted document . There are new mouse models

that do not have a bal l. They use a laser to s ensethe motion of the mouse inste ad.

Trackballs

Tr ackball is a movable ball, on top of a sta t ionary

device , tha t i s ro ta ted with the f ingers or palm of

the hand.

Advantages of t rackball a re that , i t does not nee das m uch des k space a s a m ouse , and it is no t a s

t i r ing s ince l e s s m ot ion is ne ede d . On the o the r

hand i t requi res f ine c ont rol of the bal l with jus t

one finger or thumb.

Joysticks

A joyst ick is a point ing device that cons is ts of a

vert ical handle l ike a gear shift lever mounted on a

base with one or two buttons. Joysticks are

commonly us ed in video g ame s to c o ntrol the

cur s o r m ot ion . A joys t i ck g ives a more na tu ra l

feeling of control for motion in games, especial ly

thos e in which one is mimicking flying a plane o r

spaceship .

Right Button

Left Button


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Touch screens

T ouc h s c r e e n i s a v i d e o d i s p la y s c r e e n t h a t r e c e i ve s

input f rom the touch of a f inger or s ty lus . Touch s cree ns

are of ten us ed in Automat ic Te l ler Machines (ATMs) in

banks .

Light Pen

The l ig h t p e n i s a l ig h t - s e n s i t iv e s t y l us , o r a p e n l ik e

device connected to the computer. The user can bring the

pen to the desired point on the screen. When pen touches

the screen, it sends the information available at the

location to the computer.

Scanners

Scanners generally convert text , drawings and

photographs in to digita l form that c a n be s to r e d in a

computer and then manipulated. Sometimes these

scanners are ca l led image s canners or graphics s canners .

The re a re spe c ia l pu rpose sc anner s s uch a s f inge rp r in t

s c a n n e r s w h i c h a r e u s e d t o s c a n f in g e r p r i n t s a n d b a r

c o d e r e a d e r s w h ic h r e a d t h e z e b r a - s t r i pe d m a r ks

which you se e on some products .

Barcode readerFingerprint scanner

Image scanner


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1.2.1.2 Processors

You might now wonder how can a computer proc es s

data into information. This job will be done by mea ns

of electronic circuitry inside a c omputer known as the

processo r . The p rocesso r i n a pe r sona l com pute r

(PC) i s gene ra l ly cons idere d as the P C 's "bra in". The

processor does exactly what the name implies i t

does, i t processes instructions. I t processes

ins t ruct ions and a lso manipula tes data . This wi l l be

ex plained in deta il later.

1.2.1.3 Storage or memory devices

The computer operates based on a set of instructions given by the user. If i t is a datap roc es s ing applica tion , da t a w i ll be f ed to the com p ute r w i th a se t o f necessa ry

ins t ruc t ions w hich is ca l led a c om pute r p rogram . The se da t a and p rogram s , w hen

they a re f ed , shou ld be s to re d ins ide the com pute r dur ing the p roces s ing . B ut t he

computer will ge nera lly s tor e these informat ion, data and progr ams te mpor ar i ly .

When the computer is switched off , information store d will disappear. This s torage is

r e f e r e d t o a s t h e P r i m a r y s t o r a g e w h e r e b o t h d a t a a n d pr o g r a m s a r e t e m p o r a r il y

s tored. Before you s witch off your computer data and instructions should be

p e r ma n e nt ly s t o r e d for la t e r or f u t u r e u s e . T h e d e v i c e s u s e d t o s t o r e d a t a in a

re la tively permanent form are ca l led Secondary s torage . Thus , there are two types

of storage de vices namely:

Primary storage devices and

Secondary s torage de vices

Primary storage or memory devices

Primary memory i s d i rec t ly acces s ible by the proce ss ing uni t of the co mputer. You

can store and retr ieve data much faster with primary memory compared to secondary

memory. Deta i l s of pr imary memory and pr imary memory type s c an be found in the

se ction 1.2.4.

Secondary Storage

Seconda ry s t o r age or m em ory i s de s igned to s to re ve r y la rge a m ount s o f da t a fo r

e x t e n d e d p e r i o d s o f t im e . S e c o n d a r y s t o r a g e c a n h a v e l a r g e m e m o r y c a p a c it y o f

g igaby tes o r m ore , w hereas on ly sm a l l po r t ions o f t ha t da t a a re p laced in pr imary

storage at any one t ime. Secondary storage has the following characterist ics:


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It is nonvolatile (i.e. data is not lost whe n elec trical power is switche d off).

It t akes m uch more t im e to r e t r i eve da t a f rom secondary s to rage than i t

does from main memory.

Secondary storage devices appear on a variety of media, each with i ts own

technology, as discuss ed be low.

Magnetic tapes

Magnet ic tape i s th in plas t ic tape on which data ca n be repre se nted wi th magnet ized

spots . The magnet ic tape use d for computers , is made f rom the same mater ia l used

for audiotape a nd videotape .

Magn e tic tape is k e p t o n a la r g e o p e n r e e l o r in a s m a l l c a r t r i d g e o r c a s s e t t e .

Al though th is i s an o ld t echno logy , it r e m a ins popu la r be caus e i t is t he chea pes t

s torage medium and can handle e normous amount of data . The downs ide i s tha t it i s

t he s l o w e s t f o r r e tr ie v a l o f d a t a , b e c a u s e a l l t he d a ta a r e p l a c e d o n t h e t a pe

sequent ia l ly . Sequent ia l access means that the sys tem might have to run through a

major part of the tape, before i t comes to the desired piece of data.

Magnetic disks

Magnet ic d isks come in a var ie ty of s ty les and are ext r emely popular bec ause the y

allow much more rapid access to data as compared with magnetic tape. The magnetic

d i sk i s l ike a phonograph r e cord in tha t i t has t r acks , and l ike a p i zza in tha t i t i s

d iv id e d in t o w e d g e s t h a t a r e c a l le d s e c t o r s . E v e r y p i e c e o f d a t a h a s a n a d d r e s s

a t t ached to i t co r r e spond ing to a pa r t i cu la r t r ack and se c to r . Any p iece o f des i r ed

da ta can be r e t r i eve d in a non- se quen t ia l m anner , by d ir e c t a c c e s s . A r ead - w r it e

head use s the data addre ss to quickly locate and read the data. Unlike magnetic tape

the s yste m does not have to re ad through all the data to f ind what it wants.

Hard drives

H ard d r ives use s t a cks o f r i g id magne t i c

disks. These disks are permanently

mounted as a uni t tha t may be in ternal or

exte rnal to the computer. The data

t r ans fe r r ing to and f rom the com pute r i s

h a n d le d b y t h e r e a d / w r i t e h e a d s . T h e

read/wri te heads are a t tached to arms that

hover over the disks moving in an d out .

The y r ead the da t a w hen pos i t ioned ove r

t he c o r r e c t t r a c k a nd w he n t he c o r r e c tHard Disks


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14

se c to r sp ins by . Beca use the head f loa t s j u s t above the s u r f ace o f t he d isk ( a t 25

mil lionths of a mete r ) , any bi t of dus t or conta minat ion can dis rupt the device . For

that reason, hard dr ives are hermet ica lly se ale d whe n manu fact ure d. A modern

pers onal computer may have s eve ral gigabytes of storage c apacity in its internal hard

dr ive . Da ta acce ss i s ve ry f a s t , m easure d in m il li s econds . For t hes e r e asons , ha rd

disk drives are extre mely popular and common.

Magnetic diskettes or Floppy Disks

Magnetic diskettes are commonly called floppy disks

and function similarly to hard drives , but with some

key differe nce s. A floppy disk is a re movable r ound,

f la t p iece o f p la s t i c t ha t s to res da t a and p rogram s

as magnetized spots. This is enclosed in arectangular p las t ic cas e . The bas ic s ize s of the

diskettes are 3inch which is now more popular and

5 inch . A f loppy d r ive cop ies o r r eads da t a f rom

disk and writes or records data to the disk.

Diskettes are often called floppy because the disk

with the case is f lexible. They are much slower than

hard d r ives . The y have m uch le s s capac ity , r ang ing from 1 .44 m egaby t es fo r a

s tandard high densi ty d isk to 200 megabyte s for a d isk format ted for a z ip dr ive (on

which the data ar e compress ed) . Fur ther , a l though they are individually inexpens ive

floppy dis ks ar e less c o s t -ef f ic ient than hard dr ive s t ora ge . However , the bigadvantage of f loppy disks is that they a re portable.

Optical Disks

An Optical Disk i s a re movab le disk on

w hich da t a is w r i t t en and r ead th rough

t h e u s e o f a la s e r b e a m. F e w t y p e s o f

optical technologies are used in

computers . They are :

Compact Disk Read - Only Memor y

(CD- ROM)

Write Once Read Many Disk

(WORM)

Rewritab le Compact Disk

CD ROMs

Floppy disks


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Compact Disk- Read Only Memory (CD-ROM)

Compact Disk Rea d - Only Memor y (CD- ROM) s to rage device s fea tur e h igh

capac i ty , low cos t , and h igh durab il it y . H oweve r , becaus e it i s a r ea d - on ly

medium, the CD- ROM can only be re ad and not writte n on.

Write Once Read Many Disk (WORM)

Write Once Rea d Many Disk can be writ ten or re cor ded onto once and then

cannot be eras ed. But it can be rea d many t imes .

Rewritable Compact Disk

Rewr itab le Compact Disk s allow user to re write onto the CD.

Digital Video Disc or Digital Versatile Disc (DVD)

DVD was originally called Digital Video Disc but is

now known as Digital Versati le Disc. While most

attention has bee n placed on DVD- video, the most

impor t an t a spec t o f i t f or som et im e to com e i s

said to be computer-based DVD drives as

p ro gr a ms s t a r t t o o u t s t r i p t h e c a p a c i t y o f C D-

ROMs. About 5 minutes of digital video re quires

abou t 1 g igaby te o f s to rage and so r ough ly on ly

about 3 minute s worth wil l f it on a CD - ROM.

While a DVD disc is the sa me s ize as a CD- ROM,

a n d b o t h s t o r e d a t a i n t h e s a me w a y , a s i n g le

l a y e r o f a D V D c a n h o l d a b o u t s e v e n t i m e s a s

m u c h d a t a a s a C D- ROM a n d t h e r e c a n b e t w o

layers per side and the disc can be double sided.

1.2.1.4 Output Devices

The se devices a l low the computer to output informat ion for the benef i t of the use rs .

Output can be printed on pape r or othe r per manent media. This is called a hard c opy.

Also it can be displayed on a scre en or output by other non- permane nt means . This

is called a s oftcopy s uch as on a f loppy disk.


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Monitor /Visual Display Unit

The device that d isplays computer output to us

has var ious names s uc h as monitor , scr ee n,

Visual Display Unit (VDU) etc. There are a

variety of them. First we can group themaccording to the range of colors they can

display. There are two types :

Monochrome display s c r eens

Colordisplay s c r eens

Monochrome d isp lay s c r eens can d i sp l ay on ly one color text on single color

background, i .e . white let ters on blue, or green characters on black. In color screens

various colors can be displayed.

Another way of grouping them is base d on their interna l structure . The mos t common

type of monitor use s a c athode ra y tube (CRT ). Liquid Crys tal Display (LCD) s c r e e n s

are used in laptops. This is a good solution especial ly if you do not have desk space

for a large CRT monitor or you ne ed a por table computer . Plasma scree ns a re used

for very large s cree ns and in some modern laptops . They ar e f la t scre ens wi th good

color, but are quite expe nsive.

Printers

The job of a pr in ter i s to put on paper what you se e on your moni tor . How easy andhow succe ss fu lly it i s done depe nds on the c ho ice o f your p r int e r . Se l ec t ion o f a

pr in ter i s base d on many parameter s s uch as cos t , speed, type of paper use d, qual ity

or r es olution, size, type of cable conne ction etc.

There ar e d i f fer e nt types of pr in ters . T he

les s expens ive bu t a no i sy ve r s ion i s a D ot

m a t r ix p r in t e r w h e r e a s e x p e n s i v e o n e s a r e

ink je t and l a se r p r in t e r s . Thes e a re capab le

of producing high qual ity pr in touts and the i r

biggest advantage is that they are noiseless.


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Plotters

A plotter is a spe cialized output de vice des igned to

produce high-quali ty graphics in a variety of colors.

Plotters are especial ly useful for creating maps and

archi tec tura l drawings , a l though they may a lso produce

less complicated charts and graphics.

Speakers

Speaker s ou tput sound such a s a l e r t s , m us ic , vo ice e t c .

Voice output is now possible via sophisticated

synthesizer software that can be instal led in most

pe r sona l com pute r s . A vo ice ou tpu t sys t em cons t ruc t s

the sonic equivalent of textual words, which can be

played through speakers .

1.2.1.5 Communication hardware

Communication hardware facil itates the connection betwe en individual computers and

groups of computers. Details of Communication hardware can be found in section 1.4.


1. Go to your computer resource center and note each different type of computer in

use and find out what type of applications are run on each type.

2. Identify the hardware components of a computer system in the school computer lab.

3. Go to different computer vendors and find out the configurations of few personnel

computers. Check and compare the following: Name and type of microprocessor, clock

speed, size and type of memory, size and type of secondary storage, input and output

devices, warranties and any other additional features.


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1.2.2 History of Computers

Wh a t d o y o u k n o w a bo u t t he h i s t o r y o f c o m p ut e r s ? T h e h is t o r y o f c o m p u t e r s i s

u n iq u e b e c a u s e o f t h e f a c t t h a t i t is r e a l ly v e r y r e c e n t a n d f u ll o f c o n t r o v e r s y .

Because i t is ve ry re cent , we have the abi lity to learn what happened f irs thand f rom

the pioneers .

H um an a t t em pt s t o c re a t e t oo l s t o m an ipu la t e num bers da t e back a t l eas t a s f a r a s

3000 B.C. All the earl ier efforts to juggle numbers had two things in common. They

w e r e m e c h a n i c a l a n d m a d e u p o f p a r t s b i g e n o u g h t o b e a s s e m b le d b y h a n d . T o

explore the history of computers we will look at the following topics:

Early Computational Devices

Early Computer s

Generations of Computers

1.2.2.1 Early Computational Devices

The ear l ies t computational devices were used to do th ings l ike kee ping track of days,

count animals , e tc . T o do that humans us ed the f ir s t th ing that you probably used to

coun t any th ing ; your f inge r s . W hen the re w ere too m any th ings to keep t r ack o f ,

using fingers and toes , they used s t icks, knots in ropes, etc.

Somewh er e around 3000 BC the f ir s t (probably) mecha nical count ing device was

cre ated and was c a l led the a bacus . The abacus i s s t i ll use d today, by some Chines e

t rade rs wi th fa i r spee d and accuracy. In 1642 anothe r mechanical device ca l led the

Pascal ine was cre ated. (af ter Bla ise Pas cal , a famous French mathemat ic ian) . The

Pasca l ine us ed ge a r s and w hee l s ( " coun t ing - w hee l s ") t o pe r fo rm the ca l cu la t ions .

The interes t ing thing to note is that the counting - whee l des ign was use d in

calculators unti l

t he 1960s .

Pascaline


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The next major breakthrough in computer h is tory revolves round Char les Babbage

and his Differe nce Engine and Analytical Engine. T he machines that Charles Babbage

designed in the early 1800s were not electronic computers as we know them now but

they were genera l purpose computat ional devices that we re des igned to be dr iven byste am engines. Charles Babbage is cr edited with being the "Father of Computing" due

to the fac t tha t h is des igns we re way ahe ad of h is t ime. He thus la id the foundat ion

for the modern computer.

The Difference Engine. Charles Babbage The Analytical Engine.

1.2.2.2 Early Computers

T h e n e x t m a jo r a d v a n c e s a n d t h e r e a l

beginning of the computer age took

place in the mid 1940s . Pr ior to that the

definit ion of com pu te r was , "a person

who performs computations" . Part of the

war effort revolved around human

computers performing calculat ions for

bomb trajectories.

The se c a lcula t ions required ex t reme pre cis ion and took quite a b i t of t ime. One of

t he r ea sons fo r t he deve lopment o f t he f ir s t com pute r , t he E lec t ron ic Num er ica l

Integrator and Computer (ENIAC), was to automate the calculations of bomb

bacus

ENIAC


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tra jec tor ies . T he inventors of the ENIAC went on to cre ate the Universa l Automat ic

Computer (UNIVAC), the firs t c ommer cial computer.

These f i r s t computers were ext remely

large, slow, and inefficient. Many advances

have t aken p l ace be tw ee n the c rea t ion o f

the ENIAC and now. Among the most

interest ing and pert inent to us in the

history is the development of the

microcomputer. The major development of

the microcomputer took place in the

1970s .

Dur ing th is pe r iod we have wi tness ed the

emergence of highly profitable

multi- national cor por ations includingMicrosoft , Apple, Dell , Compa q, etc . an d

the g row th and p r os pe r i ty o f p ionee r ing

compa nies like IBM.

1.2.2.3 The First Generation (1951-1958)

The f ir s t ge ne ra t ion o f com pute r s t ook

p la c e d u r in g t h e m i d 1 9 4 0 s t o t h e l a t e

1950s . The computers tha t were

developed dur ing th is t ime us ed vacuum

tubes and wir e s for the ir c i rcui t ry . If

you've ever had or been around a

vacuum tube television, radio, or

ampl i f ier you know that , when they are

left on for a length of t ime, they ge t ver y

hot and like light bulbs, they burn out. In

addition to vacuum tubes, the first-

generation compute rs us e d magnetic

drums for main memory.

The use of magnet ic drums and vacuum tubes made thes e computers e xt remely large

and bu lky . The f ir s t gene ra t ion o f compute r s a l so w e re ve ry e xpens ive to ope ra t e ,

gene rate d a lot of heat , use d a lot of electr ici ty, and fai led often. T he pr ogramming of

these computers requi red that wires were disconnected f rom one place and

connec ted to ano the r o r t ha t one c i r cu it w as tu rned on and ano the r t u rned o f f . Al l

Vacuum Tubes

UNIVAC


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programming during this ge nera tion was done in Machine Language - the language of

the machine.

1.2.2.4 The Second Generation (1959-1963)

The se cond genera t ion of computers took place dur ing the la te 19 50s to mid 1960s .Dur ing th is per iod, there was a shi f t of emphasis f rom vacuum tubes to t rans is tors

and the use of t rans is tors a l lowed radios , TVs, amplif iers , and computers to become

much smaller , faste r and less ene rgy consuming.

Programming languages evolved from the machine

language us ing the binary 1 and 0 to s omething c lose r to

the language of humans. These languages known as

ass emblers and ear ly h igh leve l languages were eas ier to

use by pe op le bu t r equ i r ed m ore w ork by the c om pute r .

The y w er e s t il l a f a r c ry f rom Engl ish , t he language w e

use for communicat ion. Companies that were purchas ing

com pute r s dur ing th i s time w e re us ing them m os t ly fo r

accounting purposes and interacted with the computer via

punched car ds for input and printed pape r for output. The

storage capacity was greatly increased with the

introduction of magnetic disk storage and the use of magnetic core s for main storage .

H igh speed ca rd r eade r s , p r in t e r s , and m agne t i c t ape un i t s w ere a l so in t roduced .

In t e rna l p rocess ing spe eds inc reas ed and w e re m easure d in mi ll ion ths o f a s e cond

(microseconds).

1.2.2.5 The Third Generation (1964-1979)

The th i rd ge nera t ion of computers be gan dur ing the mid 1960s and las ted unt i l the

mid 1970s. Computers became much smaller , much faster , and much more affordable

due to the adve nt of the in tegra ted

circuit . The use of si l icon chips or

integrated circuits (IC) brought

abou t t he des ign and deve lopm ent

of the minicomputer (mult i- user

desk sized computers) . I t was

during this t ime period that humans

began to interact with co mput e rs

directly through the use of

First Integrated Circuit (IC)

Transistors


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terminals with keyboards and monitors.

The s maller c ircuit s a l lowed for fas ter in ternal

process ing speeds resul t ing in fas ter execut ion

of instructions. Internal processing speeds were

measured in billionths of a second

(nanoseconds) . The fas ter comput er s made it

possible to run jobs that were considered

impractic al or imposs ible on firs t or se cond

generation equipment. Because the miniature

components were more rel iable, maintenance

was re duced. New mass s torage was in t roduced

during this ge nera tion, giving a s torage capacity

of ove r 100 m il li on cha ra c t e r s . Drum and d isk capa c i t i e s and spe ed have be en

in c r e a s e d , t h e p o r t a b l e d i s k p a c k h a s b e e n d e v e l o p e d , a n d fa s t e r , h ig h e r d e n s i ty

magnet ic tapes have come into use . Considerable improvements were made to card

readers and printers, while the overall cost has been greatly reduced.

Manufacturer s of third gene ration computers produce d a s e r ie s of similar and

compatible computers. This al lowed programs writ ten for one computer model to run

o n mo s t la r g e r m o d e ls o f t h e s a m e s e r i e s . Mo s t t h ir d g e n e r a t i o n s y s t e m s w e r e

designed to handle both scientif ic and business data processing applications.

Im p r o v e d p r o g r a m a n d o p e r a t i n g s o ft w a r e h a v e b e e n d e s i g n e d t o p r o v id e b e t t e r

control, resul t ing in fas ter proc es s ing. Thes e enhancements we re of s igni f icant

impor tance to computer us er s .

1.2.2.6 The Fourth Generation (1979- Present)

T h e c o m p ut e r s o f t h e f ou r t h g e n e r a t i o n w e r e n o t

easily dist inguishe d from earl ier gene rations, yet

there were some str iking and important differences.

The manufacturing of integrated circuits has

advanced to the po int w her e thousands o f c i r cu it s

can be placed on a s i licon wafer only a f rac t ion of

an inch in s ize . This has led to what i s ca l led large

scale integration (LSI) and very large scale

integra t ion (VLSI) . As a resul t of th is technology,

compute rs w er e s ign i fi can t ly sm a l l e r i n phys i ca l

size and lower in cost . Yet they have retained large

memory capaci t ies and are u l t ra fas t . Large mainframe computers are increas ingly

A third Generation Computer

A modern microchip


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c om ple x . Me d iu m s i z e d c o m p u t e r s c a n p e r f o r m t h e s a m e t a s k s a s l a r g e t h i r d

genera t ion com pute r s . An en t i r e ly new bre ed o f com pute r s ca l led microcomputers

and minicomputers have become s maller and less expens ive , and yet they provide a

large amount of computing power .

1.2.2.7 The Fifth Generation (Future)

Computers of this ge ne ration make us e of parallel proces sing and they are capable of

per forming multiple, simultane ous instructions using more than one micro proce ss ing

chip.

The following Table summarizes the Evolution of computers.

Evolution Focus Achievements Important People

3000 B.C. Abacus Chinese

Arithmetic Machine Blaise Pascal

'Difference engine' Charles Babbage

Analytical Engine Charles Babbage

The zeroth

generation

Mechanical

computers.

Mechanized system of punched

cards with holes

Herman Hollerith

Vacuum tubes - COLOSSUS Jon Ambrose Fleming

Digital computer- ENIAC Eckert, Mauchley,

John Atanasoff

The First

Generation

Electronic

computers

using vacuum

tubes

Von Neumann machine

EDSAC (first stored program

computer)

John von Neumann

A fifth Generation Computer

This gene ra t ion o f com pute r s r ep resen t s a

unification of four separate areas of

research:

Artificial lnte lligenc e

know ledge- based e xper t s ys t em s

very high- level programming languages

decentralized computing

very large- sc ale integra tion technology

(VLSI).


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Invention of the transistor John Bardeen, Walter

Brattain, and William

Shockley

The

Second

Generation

Electronic

computers

using

transistors Beginning of the minicomputer Kenneth Olsen

Evolution Focus Achievements Important People

Silicon integrated circuits

Small-scale integrated (SSI)

circuits

Medium-scale (MSI) integrated

circuits

Robert NoyceThe Third

Generation

Electronic

computers

using

Integrated

Circuits

IBM system/360

The Fourth

Generation

Computers

using VLSI

devices

Very large scale integration

(VLSI)

DEC Alpha True 64 bit

processor

The Fifth

Generation

Intelligent

Computers

Use of parallel processing,

performing multiple,

simultaneous instructions using

more than one microprocessing

chip.

1.2.3 Microprocessor Development

S i n c e t h e d a y s o f t h e fir s t v a c u u m t ub e c o m p u te r , d e s i g n e r s h a v e s o u g h t be t t e r ,fa s t e r, and cheape r com pute r pe r fo rm ance . Im provem ent s i n t hese a r eas d i r ec t ly

mirror the evolution of electronic device technology from vacuum tubes to

transistors, integrated circuits , Large Scale Integration (LSI), and Very Large Scale

Integr a t ion (VLSI) . Impor tant mi les tone s a long the way include the in t roduct ion of

integr a ted c i rcui t s ( IC) in 1964, and the in t roduct ion of the microproce ss or - of ten

called the microproce ss ing unit or , more commonly, central proces sing unit (CPU) -

in 1971.

1.2.3.1 What is a Chip or Integrated Circuit (IC)?

The integr a ted c i rcui t or chip i s a smal l, th in piece of

si l icon onto which the transistors , re sisto rs , capac itors

and diodes , are e tched according to a g ive n c i rc ui t

des ign. A chip might be as large as an inch on a s ide

and can contain tens of mill ions of transistors. Simpler

processors might consis t of a few thousand t rans is tors


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e tched on to a ch ip jus t a f ew m i l l im e te r s squa re .

The transistors act l ike switches and can turn

electricity ON and OFF or these can amplify

current . The refore , i t is use d in computers to s tore

information and is used in computer memory.

Microprocessors

A microprocessor is a single chip that contains the entire Central Processing Unit of

a com pute r . It does the bu lk o f t he p roce ss ing and con t ro ls t he r e s t o f t he sys t e m .

M ic roprocesso r s a r e no t on ly used by com pute r s . They a re used in m any dev ices

such as TVs, telephones, motor cars, or traffic l ights, etc. For example, a

microprocessor lets your phone redial or determine the timing in a traffic light

sys t em .

1.2.3.2 The Central Processing Unit CPU

The Cen tra l P rocess ing Unit (C PU ) pe r fo r m s the ac tua l com p uta t ions ins ide a

computer. The CPU is a made up of millions of micros copic transistors embedde d in a

c i rcuit on a s i l icon wafer or c hip . Hence microproce ss ors are commonly re fer re d to

as c hips. Some microprocess ors a re l iste d in the table 1.1.

Table 1.1 Examples of Microprocessors

Name Manufacturer/Year Clock Speed MHz Applications

8086 Intel / 1978 10 IBM PCs and clones

80486 Intel / 1989 -1994 20-100 IBM PCs and clones

Pentium Intel / 1993 75-200 IBM PCs and clones

Pentium

MMX

Intel / 1997 166-233 Multimedia PCs and

Workstations

Pentium ii Intel / 1997 133-450 High-end PCs and

Workstations

Pentium iii Intel /1999 450-500 Multimedia PCs and

Workstations

Pentium iv Intel / 2000 to date 500-750 Multimedia PCs and

Workstations

Pentium iv Intel / 2001 to date 1000-2500 (1- 2.5GHz)

Multimedia PCs andWorkstations

The Central Proce ss ing Unit (CPU) performs the actual proce ss ing of data. It follows

the instruction s of the progr am to manipula te data into info rmation. Th e CPU cons ist s

of three main par ts :

1. Control Unit


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2. Arithmetic/ logic unit (ALU).

3. Registers

Control Unit and ALU are c onne cte d by a kind of e le ct ronic roa dwa y called a bus as

in Figure 1.2.

Figure 1.2 Central Processing Unit

Control Unit:

The c ontrol unit controls the f low of information and instr ucts the c omputer how to

ca rry ou t p rogram inst ruc t ions . It d ir e c t s t h e m ove m ent o f da t a and ins t ruc t ions

betwe en the main memory a nd the ALU. It a l so car r ie s out the cont rol l ing of input

and output devices and passing of data to the ALU for computation.

Arithmetic/Logic Unit:

Arithmetic/Logic Unit pe rforms ar i thme tic oper ations and logical oper ations a nd

con t ro l s t he speed o f t hose dev ices . A s you know , a r i t hm et i c ope ra t ions such a s

addit ion, s ubtract ion, mult iplication, and division a re fundamental to al l mathematical

ope ra t ions . Log ica l ope ra t ions a re com par i sons . Tha t i s , t he A LU com pa re s tw o

piece s of data to s ee whether one is equal to (=), greate r than (>), or less than (


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t h e p r o c e s s i ng i s r e t u r n e d t o m a i n m e m o r y . Da t a a n d i n s t r u c t i on s d o n o t g o i n t o

either the Arithmetic/Logic Unit (ALU) or the Control Unit (CU). The ALU work s on

the data held in the re gister s acting on the instructions that are also held there .


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1.2.3.3 Computer Memory

Unlike humans who use the de cimal sys te m which has 10 digit s , computers use two

s ta t e sys t em w hich is c a l led the b ina ry s ys t e m w hich has on ly tw o d ig it s 0 and 1 .

Binary conc ep t w as o r ig ina t ed from s w it ching O N and OFF e l e c t r i c i ty . In the

computer, 0 repre se nts the electr ical curre nt OFF and 1 by the curre nt being ON. All

da t a and p rogram s tha t go in to the com pute r w i ll be r ep re se n ted in t e rm s o f t hese

numbers .

Memory Capacity

It is important to know how many 0s and 1s can be stor ed in a computer ? We ne ed to

know the memory ca paci ty . In a b inary sys tem, eac h 0 or 1 i s ca l led a bi t , which is

short for b inary dig it . To re p resen t num bers , l e t t e r s o r s pec ia l cha rac t e r s s uch a s !

or %, bits are combined into groups. A group of 8 bits is called a by te , and a byte can

repre se nt one character , d igi t or o ther value . For an example , 0100 0001 re pres ents

the let ter A. The capacity of computer memory or a diskette is expressed in numbers

of bytes. Generally, it is given in kilobytes or megabytes.

Kilobyte Kilo m eans one tho usand , s o a k i loby te (KB ) is a pprox ima te ly one

thousand bytes. Actually, a kilobyte is 1,024 (210

) by tes .

Megabyte Mega means one million, so a megabyt e (MB) is approx imate ly million

bytes . Actually a megabyte is 1,048,576 (220

) by tes .

Gigabyte Giga means one billion, a gigabyte (GB) is actually 1,073,741,824(2

30) by tes .

Terabyte Te ra mea ns one trillion, a ter abyte (TB) is actually 1,09 9,

511,627,776 (240

) by tes .

To get a fee l for thes e amounts , cons ider the fol lowing ex amples . If your computer

has 32 MB of RAM (a type of primary storage explained later), it can store

33,554,432 bytes of data . A wri t ten word might , on average , conta in 6 byte s , so th is

translates to approximately 5.6 million words

1.2.3.4 Evolution of Microprocessors

Now you know what microproces sors are and the functions of ALU. Here we will look

a t how these microproce ss ors e volved. When we look a t the te chnological advances

of m ic roprocesso r s , it is obs e rve d tha t com plex i ty o f t hese m ic roproces so r s have

increa se d significantly over the last twenty f ive ye ars.


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First Microprocessor Intel 4004

Intel 4004 which was introduced in 1971 , was the f irst s ingle

chip microprocessor as well as the f irst commercial

microproce ss or. The 400 4 was not very powerful . It was a 4

bit chip which used only 4 bits to carry out internal

processing in the CPU. Intel 4004 was originally designed to

use in electronic calculators.

Intel 8080

In te l 80 80 w as de s igne d and m anufac tured by In t e l and w as

genera lly cons ide re d a s t he f ir s t t ru ly usab le m ic roproces so r

deign. This chip was introduced in 1974. Intel 8080 was us ed in

many ear ly computers This was a 8 b it chip which was running

a t 2 M H z. A t In t e l , t he 8080 w as fo l low ed by m ore advance

Intel 8085, Intel 8086 and Intel 8088.

Intel 8086 was a 16 bit microprocessor designed and manufactured in 1978. This led

to design the x86 architecture.

Intel x86 family

x86 or Intel 80x86 was the generic name of a

microproce ss or architecture f irst deve loped and

manufactured by Intel. The architecture was ca lled x86

b e c a u s e In t e l u s e d t o g i ve t h e e a r l ie s t p r o c e s s o r s i n th is

f am ily numer i c b rand nam es end ing in the s eque nce 86 ,

the 8086, the 80186, the 80286 the 80386 and the 80486.

Intel 80386 was used in many personnel computers from 1986 unti l 1991. When Intel

80486 was int roduced in 1989 by Inte l with i t s fas ter proces s ing abil it ies i t became

more popular in pers onnel computers .

Intel Pentium microprocessors

After manufactur ing Inte l 486, In te l and other c ompet i tors s t oppe d us ing numer ic

b rand nam es fo r mic roproces so r s . They s t a r t ed to use w ord b rand nam es such a s

Pentium. Pentium processor was f irst introduced in 1993. Pentium chips offered just

under twice the performance of In te l 80486 chip . In te l microproce ss ors moved f rom

the 8088 to the 802 86 to the 8 0386 to the 80486 to the Pent ium to the Pe nt ium II to

Intel 4004 chip


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the Pen t ium III t o t he P en t ium 4 . Pen t ium 4 w as f ir s t

r e l eas ed in Novem ber 2000 . Pen t ium 4 p roces so r ca n

execute any piece of code that ran on the original 8088,

but it does it about 5,000 times faster!

With Intels announcement of releasing a new

micropr oce ss or ca lled P entium M which was for mobile

technology, a new t rend of microproc es so r indust ry

was not iced. T his technology has be en used in todays notebook computers . You are

bound to come across more and more advances in the microprocessor indust ry in the

future.

1.2.4 Computer Organization and Architecture

1.2.4.1 Basic Operations of a Computer

In th is s ec t ion we wi ll d iscus s a bout an over view of the bas ic des ign of a computer .

We will f irst check how different parts of a computer are organized and how various

operations are performed be twee n differe nt parts to do a s pe cific task. Basic

organizat ion of computer i s the same for a l l computer sys tems as shown in Figure

1.3. A computer a s shown in Figure 1.3 performs basically f ive major ope rations.

1. The input Function : acce pts data or instructions by way of input

2. The stora ge function : s tores data and instructions

3. The process ing function : proces se s data as required by the use r

4. The output function : gives re sults in the form of output

5. The control function : controls al l operations inside the computer


1. Explain the function of the Central Processing Unit.

2. Prepare a table of types of microprocessors presently available including their

specifications.

Intel Pentium 4 processor


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Each of the above opera tions can be des cribed as follows:

1. The Input Function:

This is the proce ss of enter ing data a nd ins t ruct ions into the comp ute r

sys tem. Computer takes raw data as an input and performs some process ing

giving out proces se d data bas ed on the instruction given to the computer.

2. The Storage Function:

The process of saving data and instructions permanently is known as storage.

Da ta has to be f ed in to the sys t em be fo re the ac tua l p rocess ing s t a r t s . It i s

because the processing speed of Central Processing Unit (CPU) is so fast that

the data has to be provided to CPU wi th the same speed. Therefore the data

is f ir s t s t o r e d i n t h e s t o r a g e u n i t f o r fa s t e r a c c e s s a n d p r o c e s s i ng . T h is

s torage unit or the pr imary s torage of the computer sys tem is de s igned to do

the above function. It provides s pace for storing data and instructions.

The storage unit performs the following major functions:

It s tore s al l data and instructions before and after proces sing.

I t s tores intermediate results of processing.

3. The Processing Function:

The t a sk o f pe r fo rm ing ope ra t ions l ike a r i t hm et ic a nd log ica l ope r a t ions i s

called pr oces sing. The Arithmetic/Logic Unit (ALU) of the Central Pr oces sing

U nit (C PU) t akes da t a and ins t ruc t ions f rom the s to rage un it and m ake s a l l

calculat ions bas ed on the instruc tions given and the type of data provided. It

is then sent back to the s torage unit.

Figure 1.3 Basic Organization of a computer

INPUT

UNIT

STORAGE

UNIT OUTPUTUNIT

CPUARITHMATIC/

LOGIC UNIT

Data &

Instructions Results

Data flow

Control signal flow

CONTROL

UNIT


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4. The Output Function:

T h i s i s t h e p r o c e s s o f p r o d u c in g r e s u lt s f r o m t h e d a t a f o r g e t t i n g u s e f u l

informat ion. Similar ly the output produced by the c omputer af ter proce ss ing

must also be kept inside the comp ute r before be ing given out in human

readable form. Again the output is also stored inside the computer for further

process ing.

5. The Control Function:

Control ling of a ll oper a t ions l ike input , proce ss ing, s to rage and output are

performe d by the c ont rol uni t . It takes care of s tep by s tep proce ss ing of a ll

operations inside the computer. I t controls how instructions are executed and

the above opera t ions are performed.

T h e a b o v e f u n c t io n s a r e b a s e d o n t h e m a j o r o p e r a t i o n s o f t h e c o m p u t e r , b u t n ot

direc t ly equitable to g iven hardware . As you obs er ve , a g iven funct ion may share anumber of different physical hardware. For example, the Input or Output function is

only part ially contained within the CPU. Other port ions of thes e functions are located

in other pieces of hardware.

The flow of information within the computer c an be des cribed as follows

Al l in fo rm a t ion tha t t he com pute r posses se s m us t be en te re d v i a t he Inpu t

funct ion (exce pt in spec ia l cas es where some of the computers informat ion

may be p ermanently contained within the machine)

Depending on the type of informat ion, i t may be used e i ther to ins t ruct the

computer what to do ( ins t ruct ions) or i t may be use d as data in ar i thmet ic or

logical operations (data).

As an instruction, the information tel ls the computer where the next

information is s to r e d or wh a t to do with the ne xt packe t of information

obtained.

As data, i t wil l be routed to the Arithmetic/Logic function for processing and

back to await its nex t use.

All instructions and data are place d in the memory (storage)

Ins t ruc t ions and da t a a re p rocessed sequen t i a l ly a s r equ i r ed by the s to red

program and the intermediate/f inal results are re turned to storage .

The output function displays the results of the internal processing of

information whe n called upon by t he c ontrol function.


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This conce pt derived from the above flow is ca lled the store d program concept. Basic

feature of the store d program concept is that the instructions and data must be s tored

in the memory (s torage) and ins t ruct ions are s tored sequent ia l ly in a separa te area

called program are a . S ince the ins t ruct ions are exe cuted s equent ia lly and data i tems

are picked up from the spe cified s to ra ge location, thes e co mput e rs are ca lled

sequential computers.

1.2.4.2 Von Neumann Architecture

John Von Neumann in 1946 pr e s e nte d the requirements for a genera l purpose

computer and the s t ructure of a computer tha t are s t i l l va l id today. He descr ibed a

general purpose computer as a machine containing five main units as Arithmetic and

logic uni t , cont rol uni t , memor y, input and output de vices . He la id out s ome of the

fundamental concepts inherent in the design of computer systems as:

1. The use of the binary number s ys tem

2. A single se quential ly addre ss ed memory

3. A separate arithmetic/logic unit for performing arithmetic and logical

computations

4. The store d program concept in which both the programs and i ts data are

stored in memory.

5. A controller that fetches instructions from memory and exe cutes them.

6. Th e ove rall functional organization of computer s and how the major piec es fit

together.

Ther e have be en a num ber o f a lt e rna t ive a rc h it ec tu res p roposed s ince 1946 , and a

few su ch com put e r s have b ee n bu il t , bu t t he ove rwhe lm ing m ajo r ity o f m ode rncomputers ar e bas ed on the c lassic Von Neumann Architecture

1.2.5 Memory System in a Computer

1.2.5.1 Primary Storage or Main Memory

As we know, computer memory is use d to stor e data and instructions internally in the

computer. T hes e da ta and information will be stor ed in primary stor age which is also

cal led the main memory of the computer a nd it s tor es three type of informat ion for

very brief periods of t ime:


1. Describe the organization of the main components of a computer and their functions.

2. Compare Von Neumann Architecture with some other architectures which may be

found elsewhere.


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Data to be process ed by the CPU

Instructions for the CPU as to how to proces s the data

Operating System programs that include instruc tions for computer how

to function (details c an be found in Sec tion 1.3)

As the program, which is a se t of instructions writ ten in an orde rly manner, is kept in

the main memory, the computer is able to follow thes e instructions fast . For e xample,

w hen you r e s e rve an appo in tmen t fo r a doc to r , t he c om pute r w i ll have to fo l low

se vera l s te ps to g ive you an a ppointment : take the reque s t , check the avai labi lity of

the doctor, calculate the channeling fee, wait for money to be paid, store reservation

informat ion and give a rese rvat ion number . The pr ogr am which co nta ins tho s e

ins t r uc t ions i s ke p t i n t he m a in mem ory o f t he com pute r and i s fo llowed fo r e ach

reques t .

But inside the computer, the steps followed are quite different from what we can seeon the d isp l ay un i t . As you under s t and , bo th da t a and ins t ruc t ions a re s t o re d in

com pute r m em ory in the b ina ry fo rm . The com pute r t akes da t a and ins t ruc t ions in

decimal and/or char acte r form, con ve r t s the m into binar y form, proces se s them

producing an output in b inary form and a gain conver ts the binary o utput to dec imal

and/or character form for the use r.

There are four main types of primary storage:

Registers

Random Access Memory (RAM)

Read - Only Memory (ROM).

Cache Memory

Registers:

Since the pr oces sing of data within the CPU takes place a t high spe ed, i t is ne ces sar y

t o t r a n s f e r t h e p r o c e s s e d d a t a t o o a t h ig h s p e e d . S o c o m pu t e r u s e s a n u m b e r o f

spec ia l m em ory un it s c a l led r eg i s t e r s w hich a re loca t ed ins ide the C PU. Reg i s t e r s

s tore data and ins t ruct ions temporar i ly and pass i t on as d irec ted by the c ont rol unit

of the CPU. Regis te rs have the leas t capaci ty , s tor ing ver y limi ted number of data

and instructions only immediately before a nd after proces sing.

Random Access Memory (RAM)

P r i ma r y s t o r a g e p r o v i de s b o t h t e mp o ra r y s t o r a g e f o r d a t a d u r i n g t h e p r o c e s s i n g

s ta ge , ca l led Random Acce ss Memory (RAM) and permane nt s tor age , ca l led Read -

Only Mem or y (RO M) . RA M i s m ade o f s eve ra l sm a l l s to rag e loca t ions w hich a r e

Integrated Circuits and these small storage locations are called cells . Each cell has a

unique number assigned to i t and this unique number is called the address of the cell


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and i s use d to iden t i fy the ce l l . Th i s m em or y i s l ike a l a rge ca b ine t c on ta in ing a s

m any d rawers a s t he re a re addres ses in m em ory . Each d raw er conta ins a w ord and

the addre ss is writ ten on the outside of the drawer as in Figure 1.4.

This memory i s refer re d to as the Random Acces s Memory

because the memory locations of the Random Access

Me m o r y c a n b e d ir e c t l y a c c e s s e d t o s t o r e a n d r e t r i e v e

da ta . Wheneve r t he com pute r w an t s t o w ork w i th da t a o r

instructions, they are f irst loaded in to RAM wher e the y are

held temporari ly unti l the computer needs them. Therefore,

the storage of data and instructions inside RAM is

temporary and data and information which have been

stor ed will disappear from RAM as soon a s the computer is

sw i t ched o f f . RAM is t he r e fo re a vo la t i le m em ory and i tlose s i ts content whe n the power is s witched off.

Read Only Memory (ROM)

Read Only Memory sto re s data and instructions

permanently and unlike RAM, ROM can only be read by the

CPU and cannot be written on. ROM generally stores

standard processing programs which give instructions how

to s tar t the computer and the bas ic input /output programs

that examine and in i t ia l ize var ious equipment a t tac hed t o

the compute r w hen the com pute r is sw i t ched on . The se

programs will be s upplied by the manufacture rs and will be

permanently kept inside the ROM. Data and ins tr uct ions

s to red in the R OM w i ll no t be los t on f a i lu re o f pow er

supply and there fore, ROM is known as nonvolatile

memory.

Cell ContentAddress

00100110

10100110

00111110

10101010

2002

2003

2004

2005

Figure 1.4 Depiction of a Random Access Memory

Random Access Memory


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Cache memory

T h e s p e e d o f t h e C P U is h i g h c o m p a r e d t o t h e a c c e s s t i m e o f Ra n d o m Ac c e s s

Mem ory (RAM) . There fo re the pe r fo rm ance o f t he C PU dec reas es due to the s low

speed of RAM. To decrease the mismatch in operating speed, a small memory chip is

a t tached betwee n CPU and RAM whose acc ess t ime is c lose to the proce ss ing spee d

of CPU. This memory is called Cache Memory. The CPU will f irs t re tr ieve da ta from

the Cache Memory. If the data is not available in the Cache Memory , then the data is

f ir s t loaded f rom RAM into the Cache Memory, and the n take n by the CPU from the

Cache Memory as s hown in Figure 1.5. Usually, the Cache Memory is acce ss ed much

fas te r than conve nt ional RAM. It i s used to s tor e progr ams or data c urre nt ly being

exe cu ted o r t em pora ry da t a fr equen tly us ed by the C PU . So the C ache M em o ry

makes the RAM to be faste r and i t also s upplements the RAM. Since i t is ex pensive to

have a bigger size of Cache Memory its size is normally kept small.

1.3 Software

What is software?

It i s impor t an t t o no te tha t a com pute r canno t do any th ing on it s o w n . It m us t be

in s t r u c t e d t o d o a d e s i r e d jo b . He n c e i t i s n e c e s s a r y t o s p e c i fy a s e q u e n c e o f

ins t ruc t ions tha t a com pute r m us t pe r fo rm to so lve a p rob lem . Such a se quence o f

ins t r uct ions wr i t ten in a language tha t can be under s tood by a compute r i s ca l led acomputer program.

It i s t he p rogra m tha t con t ro l s t he ac t iv ity o f p roces s ing by the com pute r a nd the

com pute r pe r fo rm s p re c i se ly w ha t t he p rogram w an t s i t t o do . The t e r m Softw are

re fe r s t o t he se t o f compute r p rogram s , p rocedures , and a s soc ia t ed document s . To

be pre cise , sof tware me ans a col lec t ion of programs whose object ive i s to enhance

the ca pabil it ies of the har dware .


1. Discuss the difference between different primary storage devices.

2. Explain what cache memory is and explain how it is different from main memory.

Random Access

Memory (RAM)

Cache

MemoryCPU

Figure 1.5 Arrangement of Cache Memory


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1.3.1 Types of Software

Computer s oftware is normally class ified in to two broad cate gories:

Application Softwar e

System software

Application software is usually custom writ ten or packaged and i t enables the user to

perform their work (example Microsoft Word). Syste m software e nables the computer

to run application software (example Microsoft Windows).

1.3.2 Application Software

An Application Software also referred to as an

a p p lic a t i o n p a c k a g e , is a s e t o f p r o g r a m s d e s i g n e d t o

carry out operations for a specified purpose. For

e x a m p l e , a p a y r o l l p a c k a g e p r o d u c e s p a y s l ip s a s t h e

major output and an application package for processing

examinat ion res ult s produces mark shee ts as the major

output along with some other s tat ist ical reports .

Simi lar ly , a program wri t ten by a sc ient i s t to solve his

par t icular res earc h problem is a lso applica t ion s of tware .

The programs that cons t itu te an appl ica t ion package are

known as application programs and the person who

prepa res application programs is known as an application

programmer.

1.3.3 System Software (Operating System)

When you s w it ch on the c om pute r , t he p rogram s s to red in the R ead - Only Mem ory

(ROM) is e xe cuted which act ivates d i ffere nt unit s of the computer . T his makes the

computer re ady for you to work on i t . The se progr ams are ca l led sys tem sof tware .

Ther efore , sys tem s of tware may be def ined as a s e t of programs des igned to cont rol

the ope r a t ion o f a compute r sys t em . There fo re , sys t e m so f tw are i s a lso ca l led a s

Operating Syste m.

System Software generally performs tasks such as controll ing al l operations required

to move data in and out of the computer. I t communicates with printers, card readers

disk e tc . , and monitors the us e of hardware such as memory, CPU etc . A computer

c a nn ot w or k w i t h o u t a n o p e r a t i n g s y s t e m . Sy s t e m So f t w a r e a l lo w s a p p li c a t io n

sof tware to be r un on the computer wi th les s t ime and e f for t . Appl ica t ion sof tware

cannot be r un without having sys tem s oftware .


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Figure 1.5 Relationship among hardware, software and the user of a computer system

Some common operating systems are DOS, various versions of

Windows , OS/2 , UNIX, and Linux. All the se be have in ver y

di f ferent ways and have di f ferent hardware requi rements and

they will not run on all machines.

The creat ion of sys tems sof tware i s a complex task . Sys tems

programmers , who prepare sys tems sof tware , are h ighly

t r a ined com pute r spec ia li s t s and impor t an t mem ber s o f t he

computer architectural team. Because of i ts technical

com plex i ty , sys t em s so f tw are i s r a r e ly deve loped in - house .

They are normally developed and distr ibuted by co mpu te r

manufacturers .


1. List the differences between application software and system software.

2. Explain why a computer is not useful without the system software.

User

System Software

Application Software

Hardware


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1.4 Communication and Computer Networks

1.4.1 Introduction to Communication

The Romans us ed the Latin word communication when they me ant to make common,to s hare, or to impart.

Comm unica t ion i s t he sh a r ing o f in fo rm a t ion o r m es sa ge s be tw e en tw o o r m ore

ent i t ies .

Why do we communicate?

I want to

v Discuss some subject matterv Inform my abilities to another person

v Get an appointment

v Have a c hat with my friend

v T ransfer a file

v Send e - mails

v SMS!


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1.4.2 Components of a Data Communication System

We a l l a r e fam ilia r w i th som e so r t s o f com m unica t ion in our day to day l i fe . For

communicat ion of informat ion and mes sage s we s omet imes use te lephone and pos ta l

communicat ion sys te ms. Similar ly data and informat ion from one compute r s ys t em

can be t r ansm it t ed to o the r sys t em s ac ros s geogr aph ica l a r e as . T here fo re , da t a

transmission is the movement of data or information using some standard

communicat ion methods s uc h as e lec tr ica l s ignals ca r r ied a long a cond ucto r or

microwave link or optical signals along an optical fiber etc.

Suppose your teache r wants to se nd some tutor ia ls to h is s tudents , and he wants to

use his computer to s end these tu tor ia ls , how can he s end those? Fi rs t, he has to use

his PC and Word Proc es s ing package to pre pare the tu tor ia l. I f the teac hers PC is

connected to the computers of s tudents through networking, he can se nd the tu tor ia l

to a ll s tude nts wi thin minutes . Thus i r re spe ct ive of geograph ical are as , if PCs areconnected through communication channel, the data and information, computer f i les

and any other program can be transmitted to other computer systems within seconds.

The s tudent a lso can s end some acknowledgments of the r ece ipt of the tu tor ia l sent

by teachers us ing the same network.

Communicat ion is a proce ss of t ransfer r ing mes sage s or informat ion f rom one point

to ano the r . We can iden t i fy th ree ba s i c e l em en t s o f any com munica t ion p roce ss .

Those a re :

The Sender

The Medium

The Receiver

For ex ample , when you spe ak to your f r iend over the te lephone, you are the s e n d e r .

The te lephone l ine through which your voice i s t rans mit ted i s the medium and your

friend is the r e ce ive r . The same concept pe rtains to data communication too.

Teacher = sender You =receiver

Medium

MessageMessage


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Data c ommunication is the function of transpor ting data from one location to anothe r.

In th is ca s e the se nde r an d the r ece ive r a r e norm ally m ach ines , in pa r t icu la r ,

computer devices (computers, terminals, peripheral devices l ike printers) .

A communication system consists of hardware and software that transmits

info rm a t ion from one loca t ion to ano the r . The se sys t em s ca n t r ansm i t t ex t , da t a ,

graphics , voice , documents , or full- motion video information.

Communication Model

To transmit information between two locations, i t is necessary to have a t ransmi t te r ,

rec eiver and a t rans miss ion medium , which provides the connection as in Figure 1.6 .

To transmit and rec eive information, a communication syste m must per form a numbe r

of separate functions. The system must do al l of the following: transmit information,

e s t ab l ish the in t e r face be tw een the s ender and the r e ce ive r , rou te m es sages a long

t h e b e s t p a t h , e n s u r e t h a t t h e r i gh t m e s s a g e g e t s t o t h e r ig h t r e c e i v e r , c h e c k t h e

mes sage fo r e r ro r s and r ea r r a nge the form a t if nece ss a ry , conver t m ess ages f rom

one speed to anther , ensure that the sending devices , receiving devices and

communication links are operational and secure the information at all times.

Communication Protocols

You may be wonder ing how the computers send and receive data across

communicat ion links . The re must be s ome se t of ru les to ins t ruct computer sys tems

and dev ices a s t o how ex ac t ly da t a is t o be t r ans fe r r e d f rom one p l ace to ano the r .

For example , there are some rules a nd procedures to use a te lephone network which

leads to a se quence of activit ies such a s pick up the phone, l iste n for a dial tone, dial

a number having a s pecific number of digits , wait for the phone to r ing, and say he llo.

Similarly in data communication, some s oftware de fines the pr ocedure s and sta ndards

for the communicat ion. The pr oce dure of data t rans format ion i s commonly ca l led

protocol. A protocol is a s et of rules that governs how information is delivere d.

Transmitting/

Receiving devices

ModemModem

medium

Transmit

Transmitting/

Receiving devices

Figure 1.6 Two-way transmission model


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Modem

If y ou w an t t o se nd a p i c tu re o f your f am i ly to one o f your

friends via a telephone line which transmits only analogue

signals, you may have to convert the digital image to analogue

signals and then transmit . Your fr iend will have to convert theanalogue s ignals back to the digital image. Analog s ignals vary

cont inuously; an exa mple of an analog s ignal is a s ound wave.

There fo re , in o rde r t o s end d ig i t a l s igna l s ove r an o rd ina r y

telephone l ine not de signed for digital signals, a s pecial device

cal led a mode m should be use d. Modem is the de vice that conve r ts be twee n analog

and digital signals. Digital signals, which are used by computers, are usually

repres ented by a ser ies of 1 ' s and 0 ' s . Modems are often used to enable computers to

communicate wi th each other a cros s te lephone l ines . A modem conver ts the digita l

s igna ls o f t he s end ing com pute r t o ana log s igna ls t ha t c an be t r ansm i t t ed th rough

telephone l ines. When the signal reaches i ts destination, another modem reconstructs

the original digital signal, which is processed by the receiving computer.

1.4.3 Introduction to Computer Networks

1.4.3.1 What is a Computer Network?

A compute r ne tw ork i s an in t e rconnec t ion o f va r ious com pute r s ys t em s loca t ed a t

dif fere nt p laces . In a computer ne twork, two or more computers are l inked together

wi th a medium and data communicat ion devices for the purpose of communicat ing

git sg chapter 1

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