first year lecture 1

7/21/2019 First Year Lecture 1

1/45

COMPUTER ORGANIZATION

Lecture 1


2/45

Components of a Digital Computer

A computer system is the integration of

physical entities called hardareand non-

physical entities called softare.

The hardare !omponents include input

devices, processor, storage devices and

output devices.

The softare items are programs and

operating systems so that the computer can

process data.


3/45

Computer Top "e#el $ie

The %lo!& diagram of !omputer hardare !omponents is

shon %elo

'un!tional Units of a Computer ()stem


4/45

Functional Units of a Computer System

asically any computer is supposed to carry out the

follo!ing functions.

*+ A!!ept the data and program as input+

,+ (tore the data and program and retrie#e

as and hen re-uired+

.+ Pro!ess the data as per instru!tions

gi#en %) the program and !on#ert it intouseful information+

/+ Communi!ate the information as output+


5/45

Input Unit

A !omputer uses input de#i!es to a!!ept

the data and program+

Input de#i!es allo !ommuni!ation

%eteen the user and the !omputer+

In modern !omputers &e)%oard0 mouse0

light pen0 tou!h s!reen are some of the

input de#i!es


6/45

Output Units

(imilar to input de#i!es0 output de#i!esha#e an interfa!e %eteen the !omputer

and the user+

These de#i!es ta&e ma!hine !oded outputresults from the pro!essor and !on#ert

them into a form that !an %e used %)

human %eings+ In modern !omputers0 monitors1displa)

s!reens2 and printersare the !ommonl)

used output de#i!es+


7/45

Central Pro!essing Unit

CPU is the %rainof an) !omputer s)stem+

It !onsists of arithmeti! and logi! units0

!ontrol unit and internal memor)

1registers2+

Programs 1softare2 pro#ide the CPU0 a set

of instru!tion to follo and perform a

spe!ifi! tas&+ 3eteen an) to !omponents of the

!omputer s)stem0 there is a patha) !alled

a %us hi!h allos for the data transfer


8/45


The fun!tions of the CPU are 4

*+ Co5ordinate all !omputer operations

,+ Perform arithmeti! and logi!al operations on data


9/45


Control unit !ontrols all the hardare operationsof input units0 output units0 memor) unit and the

pro!essor+

A"Uperform addition0 su%tra!tion0 di#ision and

multipli!ation as ell as some logi!al operations+

The instru!tions and data are stored in the main

memor) so that the pro!essor !an dire!tl) fet!h

and e6e!utethem+ 7hile performing these operations the A"U ta&es

data from the temporar) storage area inside the

CPU named registers+


10/45

'un!tions of a CPU


11/45

Memor) Unit

In the main memor)0 the !omputer stores theprogram and data that are !urrentl) %eing used0

main memor) store the program and data %efore

pro!essing+

The main memor) holds data and program onl)

temporaril)+

There is a need for storage de#i!es to pro#ide

%a!&up storage0 the) are !alled se!ondar)storage de#i!es+

(e!ondar) storage de#i!es !an hold more

storagethan main memor) and is mu!h less

e6pensi#e+


12/45

(tored Program Con!ept

The essentials of the stored program !on!eptare4

*+ The program and data are stored in a primar)

memor),+ The !omputer !an e6e!ute a program

automati!all)+

.+ The !ontrol unit fet!hes and e6e!utes the

instru!tions in se-uen!e one %) one+

/+ Instru!tion !an modif) the !ontents of an)

lo!ation in the stored program !on!ept+


13/45

Understanding the 7or&ing Prin!iples of CPU

Let us go through the various tas"s involved in

e#ecuting a simple program.

$his program performs arithmetic addition on t!o

num%ers. $he algorithm of this program is given %y

&. input the #alue of a

II+ input the #alue of %III+ sum 8 a 9 %

I$+ output the #alue of sum


14/45

Program e6e!uting steps

1. $he control unit %egins to e#ecute the program

instructions one %y one in a se'uential manner.

(. $he control unit signals the input device )say

"ey%oard* to accept the input for the varia%le +a.. $he userenters the value of +aon the "ey%oard.

. $he control unit recogni/es and ena%les to route the

data )value of a* to the pre-defined memory location

)address of +a*.

0. $he steps (to !ill %e repeated for the second input

+%. $he value of +%is stored in the memorylocation

)address of +%*.


15/45

rogram e#ecuting steps )Cont.*2. efore e#ecuting the arithmetic instruction, the control

unit ena%les to send a copy of the values stored inaddress of +a and address of +% to the internal

registers of the ALU and signals the ALU to perform

the sum operation.

3. $heALUperforms the addition. After the computation,

the control unit ena%les to send the copy of the result

%ac" to the memory)address of +sum*.

4. Finally, the result is displayed on the monitor. $hecontrol unit ena%les to send the copy of the values of

the address of +sum to the monitor )%uffer* and

signals it. $he monitor displays the result.

5. 6o! this program e#ecution is complete.


16/45

7or&ing Prin!iples of a CPU


17/45

Arithmetic 7perations

Arithmeti! operations in!lude addition0 su%tra!tion0

multipli!ation0 and di#ision+

7hile performing these operations0 the A"U ma&es

use of the registers+ Upon !ompletion of the arithmeti! operation0 the

result !an %e transferred from the register to the

main memor)+ In addition to registers0 the arithmeti! unit uses one

or more adders that a!tuall) perform arithmeti!

operations on the %inar) digits+


18/45

Arithmeti! Operations

$he arithmetic operation in adding t!o num%ers 0 8 4can %e demonstrated through follo!ing steps 9

(tep *4 : and ; are put into to separate memor)

lo!ations+

(tep ,4 The !ontrol unit fet!hes the to num%ersfrom their memor) lo!ations into the data registers+

(tep .4 The arithmeti! unit loo&ing at the operator 192

uses the a!!umulator and adds the to num%ers+

(tep /4 The A"U stores the result 1*.2 in memor)%uffer register+

(tep :4 Then the !ontrol unit stores the result into a

user desired memor) lo!ation0 sa)


19/45

Arithmeti! Operations


20/45

"ogi!al Operations

Some of the %asic functionsperformed %y the ALU are,

add, su%tract, logical A6:,

logical 7;, shift left and shift

right on t!os complement

%inary num%ers.

$he inputs to %e calculated

are stored in the inputregister )A; output register

)ACCU?* for add, A6: and

7; functions.


21/45

Memor) Unit

The term >memor)? usuall) refers to the mainmemor) of the !omputer+

There are different t)pes of memor)4

*+ Random A!!ess Memor) 1RAM2,+ Read Onl) Memor) 1ROM2

.+ Programma%le Read Onl) Memor) 1PROM2

/+ Erasa%le Programma%le Read5Onl) Memor)

1EPROM2

:+ Ele!tri!all) Erasa%le Programma%le Read5

Onl) Memor) 1EEPROM2


22/45

Random A!!ess Memor) 5 RAM

This is reall) the main store and is the pla!e herethe program gets stored+

7hen the CPU runs a program0 it fet!hes the

program instru!tions from the RAM and !arries

them out+

If the CPU needs to store the results of the

!al!ulations it !an store them in RAM+

It is a #olatileform of memor)+


23/45

Read Onl) Memor) 5 ROM

In ROM0 the information is %urnt 1pre5re!orded2 intothe ROM !hip at manufa!turing time+

On!e data has %een ritten into a ROM !hip0 it

!annot %e erased %ut )ou !an read it+ ROM is a non5#olatile memor)+

ROM stores !riti!al programs su!h as the program

that %oots the !omputer+


24/45

Programma%le Read Onl) Memor) 5 PROM

;7?is a memory on !hich data can %e

!ritten only once.

A variation of the ;7?chip is that it is not

%urnt at the manufacturing time %ut can %e

programmed using ;7?programmer or a

;7?%urner.

;7? is also a non-volatile

memory


25/45


26/45

Ele!tri!all) Erasa%le Programma%le Read Onl)

Memor) -


27/45

Data Representation

The smallest unit of information is a single digit!alled a


28/45

hierar!hi!al memories4

$he registers )internal memory* are used to holdthe instruction and data for the e#ecution of the

processor.


29/45

The se!ondar) memor)

The se!ondar) memor) is the memor) thatsupplements the main memor)+

The program should %e %rought into the main

memor) from the se!ondar) memor) %efore

%eing e6e!uted+

The se!ondar) memor) is !heaper !ompared

to the main memor)+

Computer generall) has limited amount of main memor) and

large amount of se!ondar) memor)+


30/45

(torage De#i!es

Bard Dis& @ard dis" is a magnetic dis" on !hich you can store

computer data.

$he hard dis" is a direct-access storage medium.$his means you can store and retrieve data randomly.


31/45

(torage De#i!es

?agnetic $apeA recording medium consisting of a thin tape !ith a

coating of a fine magnetic strip, used for recording

digital data.

its are recorded as magnetic spots on the tape along

several trac"s. Usually, seven or nine %its are

recorded simultaneously to form a character together

!ith a parity %it.


32/45

(torage De#i!es

'lopp) Dis& The flopp) dri#e uses a thin !ir!ular dis& for data

storage+ It is a soft magneti! dis&+

It is a thin magneti!5!oated dis& !ontained in a

fle6i%le or semi5rigid prote!ti#e a!&et+

The dis& rotates at . rpm+

A readrite head ma&es ph)si!al !onta!t ith the

dis& surfa!e+

Data is re!orded as a series of tra!&s

su%di#ided into se!tors+


33/45

(torage De#i!es

7ptical :is" 7ptical dis"s are a storage medium from !hich

data is read and to !hich it is !ritten %y lasers.

$he optical dis" is a random access storagemediumB information can %e easily read from any

point on the dis".

C:-;7? stands for Compact :is" - ;ead 7nly?emory.


34/45

&nput and 7utput :evices

&nput devices is also defined as a device that provides

communication %et!een the user and the computer.

For e#ample, a "ey%oard is an input device.


35/45

ey%oard

$he most common input device is the "ey%oard.

$he "ey%oard detects the "ey pressed and generates the

corresponding ASC&& codes !hich can %e recogni/ed %y

the computer.


36/45

?ouse

?ouse is an input device that controls the movement of

the cursor on the display screen.

a small %all is "ept inside and touches the pad through a

hole at the %ottom of the mouse. Dhen the mouse is

moved, the %all rolls.

$his movement of the %all is converted into signals and

sent to the computer.


37/45

Scanner and ar Code ;eader

Scanner is an input device that allo!s information such as

an image or te#t to %e input into a computer.

$he %ar-code reader scans the information on the %arcodes

and transmits to the computer for further processing.

Scanner ar code reader


38/45

$ouch Sensitive Screen and 7ptical Character

;ecognition )7C;*

$ouch Sensitive Screen is a pointing device that ena%les

the user to interact !ith the computer %y touching the

screen.

Eou can use your fingers to directly touch the o%ects on the

screen.

$he 7C; techni'ue permits the direct reading of any

printed character.

$he computer !ill recogni/e the characters in the page as

letters and punctuation mar"s, and stores. $his can %e

edited using a !ord processor.


39/45

Light en and ?agnetic ;eader

A light pen is a pointing device shaped li"e a pen and is

connected to a monitor.

?agnetic reader is an input device !hich reads a

magnetic strip on a card. &t is handy and data can %e

stored and retrieved.


40/45

?icrophone

?icrophone serves as a voice input device.

&t captures the voice data and input to the computer.Using the microphone along !ith speech recognition

soft!are can offer a completely ne! approach to input

information into your computer.


41/45

7utput :evices

An output device is capa%le of presenting information from a computer.

Monitors

?onitor is a commonly used output device, sometimes called as display

screen.

$he num%er of pi#els that can %e displayed vertically and hori/ontally

gives the resolution of the monitor.

$he resolution of the monitor determines the 'uality of the display.

Some popular resolutions are 2G # 4G pi#els, 4GG # 2GG pi#els and

1G( # 324 pi#els.


42/45

7utput :evices

Printers

rinter is an output device that prints te#t or images on

paper or other media.


43/45

7utput :evices

(pea&ers

$he computer can also give produce voice output)audio

data*.

Spea"er serves as a voice output device.


44/45

Storage :evices

$he smallest unit that can %e !ritten to or read from the

dis" is a sector.

$he storage !apa!it) of the dis" is determined as

1num%er of tra!&s F num%er of se!tors F %)tes per

se!tor F num%er of readrite heads2+

$he arrangement of trac"s and sectors on a dis" is "no!n

as its +format.

@igh data rates demand that the dis" rotates at a high

speed )a%out ,2GG rpm*.


45/45

Computer Organiation

3asi! Components of a Digital Computer Central Pro!essing Unit 1CPU2

Memor) Unit

Input and Output De#i!es

first year lecture 1

Documents