Computer Systems 3

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Introduction to Computing:Lecture 4

Computer Systems


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Overview

This Lecture covers:To learn about different memorydevices used in our computersTo learn about the ma!or part of ourcomputer" C#$ and its components as

well


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&emory 'evices

The device" which is used to store thedata" instructions and information before"

during and after the processing by (rithmetic Logic $nit )(L$*It is actually a wor+ area )physically acollection of integrated circuits* within thecomputer" where the C#$ stores the dataand instructions It is also +nown as a&ain,#rimary,Internal memory


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&emory 'evices

It is of the following three types:-.ead Only &emory ).O&*.andom (ccess &emory ).(&*Complementary &etal O/ideSemiconductor &emory )C&OS*


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&emory: .O&

1on-volatile chips inside which data orprograms are stored

henever the computer is switchedon" it searches for the re3uiredinformation or instructions The

memory which has these essentialinstructions is +nown as Read OnlyMemory (ROM).


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&emory: .O&

This memory is permanent and not erasedwhen the system is switched off

The memory capacity of .O& varies from4 56 to 20 56 etc

.O& contains a number of programs )set ofinstructions* The most important program of.O& is the 6asic Input Output System)6IOS* hich activates the hardware


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&emory: .O&

There are many types of .O&available for microcomputers li+e

&as+ .O&" #.O&" 8#.O&"88#.O& and 8(#.O&i. Mask ROM : &as+ .O& is the basic

.O& chip In this type of .O&" theinformation is stored at the time of itsmanufacturing So" it cannot be alteredor erased later on


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&emory: .O&

ii. PROM : #.O& stands for Programmable ReadOnly Memory. In this type of .O&" theinformation is stored by the programmers afterits manufacturing It also cannot be altered orerased later on

iii. EPROM : 8#.O& stands for Erasable PROM It is similar to #.O&" but its information can beerased later on by ultra violet light and it can bereprogrammed


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&emory: .O&

iv. EEPROM : 88#.O& stands forElectrically EPROM. It is similar to

8#.O&" but its information can beerased by using an high voltage currentv. EAPROM : 8(#.O& stands for

Electrically Alterable PROM. (scompared to 8#.O& ; 88#.O&" theinformation stored in 8(#.O& can bealtered later


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s main memory and is used totemporarily storage programs and data withwhich it is wor+ing

.(& is volatile )erased when the power to the#C goes off*

.(& comes in a variety of types" speeds" andsi?e


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greater than" )and not greaterthan*

x &ultiply < less than )and not less than*

'ivide greater than or e3ual to )and not greater than or e3ualto*

^ .aise by a power less than or e3ual to )and not less than or e3ual to*

ALU Operations List


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Computer Systems 3