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Introduction to Computers

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What Is A Computer?

 A computer is an electronic device, operating under

t he control of   instructions (softw

are) stored in itsown memory unit, t  hat can accept dat a (input),

manipulate dat a (process), and produce information(output) from t  he processing. Generally, t  he term isused to describe a collection of devices t hat function

toget her as a system.

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Devices t hat comprise a computer system

Printer(output)

Monitor(output)

Speaker(output)

Scanner(input)

Mouse(input)

Keyboard(input)

System unit 

(processor, memory«)

Storage devices

(CD-RW, Floppy,Hard disk, zip,«)

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What Does A Computer Do?

Computers can perform four generaloperations, which comprise t he information

processing cycle.

Input 

Process

Output 

Storage

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Simple Block Diagram

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Dat a and Information  All computer processing requires data, which is a collection of 

raw f acts, figures and symbols, such as numbers, words,images, video and sound, given to t  he computer during t he

input phase.

Computers manipulate dat a to create information. Informationis dat a t hat is organized, meaningful, and useful.

During t he output Phase, t  he information t hat has been createdis put into some form, such as a printed report.

The information can also be put in computer storage for futureuse.

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Computerization:

 Advant ages & Disadvant ages

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What are t he advant ages and disadvant ages of 

computerization of business activities (electronic dat a processing)?

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 Advant ages Speed:

Computerisation helps in processing t he dat a placed inseveral dat a files in no time. This is possible due to t he high speed of computers for processing dat a and CPU of t hecomputer works at t he speed of electricity which is t hehighest ever att ainable speed.

 Accuracy:

The d

at 

aprocessed by t 

he computer

are

hig

hly

accur

ate.The programs written on t he system checks and controls

dat a before and during processing. It detects invalid dat a and ensures high degree of accuracy and reliability of output reports.

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 Advant ages Flexibility:

The modern digit al computers can be used for a variety of purposes. E.g. online processing, multiprogramming etc.

Choice of Configuration: Wide ranges of peripherals are available for many computer

systems, which allow business organization to select t hosewhich most suit its processing requirements.

Storage capacity: Large volumes of dat a can be conveniently stored, accessed

and altered.

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 Advant ages Management information:

They can be used to provide useful information of management for control and decision making.

Reduction in paper work: The use of computers for dat a processing has helped t he

management of business organizations to cope wit h increasing problem of paper handling. The computers have

speeded up t he process

and

have elimin

ated t 

he p

aperneeds t hrough t he storage of dat a in elaborately constructed

dat a bases and files.

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 Advant ages Reduced cost:

Though t he initial investment for inst alling a computer ishigh, but it subst antially reduces t he cost of each of itstransaction. Cost reduction occurs due to processing of hugedat a and record keeping.

Diligence: Being a machine, it does not suffer from boredom, tiredness

or lac

kof concentr

ation, even if millions of comput 

ations

areto be performed by a computer. It performs t he calculations

wit h same accuracy and speed.

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Disadvant ages The initial investment can be very high.

Computers change t he usual way of working in an

Organization (Paper file passing), t his often makesemployees and management feel uneasy.

 A paper based st and-by mechanism is required in t heOrganization despite computerization to counter t heproblems arising out of power or system f ailurescenarios.

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How Does a Computer Know

what to do? It must be given a det ailed list of instructions,

called a computer program or software,

t hat tells it exactly what to do. Before processing a specific job, t he

computer program corresponding to t hat jobmust be stored in memory.

Once t he program is stored in memory t hecomputer can st art t he operation byexecuting t he program instructions one after

t he ot 

her.

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Input Devices Keyboard

Mouse

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The Keyboard

The most commonly used input device is t hekeyboard on which dat a is entered bymanually keying in or typing cert ain keys. A

keyboard typically has 101 or 105 keys.

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The Mouse

Is a pointing device which is used to controlt he movement of   a mouse pointer on t  hescreen to make selections from t he screen. Amouse has one to five buttons. The bottom of t he mouse is flat  and cont ains a mechanismt hat detects movement of t he mouse.

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The Central processing Unit 

The central processing unit (CPU) cont ainselectronic circuits t hat cause processing tooccur. The CPU interprets instructions to t he

computer, performs t he logical and arit hmeticprocessing operations, and causes t  he input and output operations to occur. It isconsidered t he ³brain´ of t he computer.

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Memory

Memory also called Random Access Memoryor RAM (temporary memory) is t  he mainmemory of t  he computer. It consists of  

electronic components t  hat store dat aincluding numbers, letters of t he alphabet,graphics and sound. Any information stored inR AM is lost when t he computer is turned off.

Read Only Memory or ROM is memory t hat isetched on a chip t hat has st art -up directionsfor your computer. It is permanent memory.

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 Amount Of R AM In Computers

The amount of memory in computers istypically measured in kilobytes or megabytes.One kilobyte (K or KB) equals approximately

1,024 memory locations and one megabyte(M or MB) equals approximately one millionlocations A memory location, or byte, usuallystores one character.

Therefore, a computer wit h 8 MB of memorycan store approximately 8 million characters.One megabyte can hold approximately 500pages of text information.

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Output Devices

Output devices make t he informationresulting from t he processing available foruse. The two output devices more commonly

usedare t 

he printer

and t 

he computerscreen.

The printer produces a hard copy of youroutput, and t he computer screen produces a

soft copy of your output.

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Storage Devices

 Auxiliary storage devices are used to storedat a when t hey are not being used inmemory. The most common types of auxiliary

storage used on personal computers arefloppy disks, hard disks and CD-ROM drives.

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Structure Of Floppy Disks Initially Floppy disks were 8-inches wide, t  hey t hen

shrank to 5.25 inches, and today t he most widelyused folly disks are 3.5 inches wide and can typically

store 1.44 megabytes of dat a.  A floppy disk is a magnetic disk, which means t hat it 

uses magnetic patterns to store dat a.

Dat a in floppy disks can be read from and written to.

Formatting is t he process of preparing a disk forreading and writing.

 A track is a narrow recording band t hat forms a fullcircle on t he surf ace of t  he disk.

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The disk¶s storage locations are divided into pie-shaped sections called sectors.

 A sectors is capable of holding 512 bytes of dat a.  A typical floppy stores dat a on bot h sides and has 80

tracks on each side wit h 18 sectors per track.

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Hard Disks  Anot her form of  auxiliary storage is a hard disk. A

hard disk consists of one or more rigid met al plates

coated wit h a met al oxide material t hat  allows dat ato be magnetically recorded on t  he surf  ace of t  heplatters.

The hard disk platters spin at  a high rate of speed,typically 5400 to 7200 revolutions per minute (RPM).

Storage capacites of   hard disks for personalcomputers range from 10 GB to 120 GB (one billionbytes are called a gigabyte).

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Compact Discs  A compact disk (CD), also called an optical disc, is a

flat round, port able storage medium t  hat is usually

4.75 inch in diameter.  A CD-ROM (read only memory), is a compact disc

t hat used t  he same laser technology as audio CDs forrecording music. In addition it can cont  ain ot  hertypes of dat a such as text, graphics, and video.

The capacity of a CD-ROM is 650 MB of dat a.

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