3. “ It is a high speed electronic device
which is capable of performing
logical and arithmetical operations .
It accepts data as an input from the
user, processes and gives desirable
DATA : They are a set of related facts,
the new material of information,
data represented by symbols, but
they are not information accept in
limited sense .
Information : The analyzed data
details is termed as information . As
used in data processing,
information is data arranged in an
order and form that is useful for
people who receive .
4. Most of people know that a computer is fast calculator . But it is much more than that ,
some of features that make a computer so important are its :-
I. Speed :- The first feature of computer is speed . It is a very fast device which can
perform any type of task in fraction of seconds. When performing a particular task
for hours together . it can maintain the same speed till the end of it .
II. Accuracy :- The word accuracy means exactness of result . The accuracy with
which a computer perform calculation or processes data is very high . It never
gives wrong information unless user does .
III. Storage :- One of the most important features of computer is storage . A computer
can store large amount of data and whenever required can retrieve it back very
IV. Versatility :- A computer can perform almost all type of arithmetical and logical
V. Automation :- A computer can perform a particular work continuous for hours
together without any user ( human ) intervention .
VI. Diligence :- A computer does not suffer from human trait or tiredness or board . If
3 million calculation has to be performed , it will perform the 3rd millionth
calculation with the same speed and accuracy as the first one .
5. Input unit Output
mouse , Iight
pen , etc . )
6. INPUT UNIT
1. Input unit :- it is a device which is used in transferring the data or
instruction to the computer system . Most commonly used input device are
keyboard , mouse , card reader, magnetic disk .
2. System unit :- it is regarded as the brain of the computer . The major
structural components of C.P.U. are –
(a) control unit
(b) Arithmetical and logical operation
(c) Memory unit
(a) control unit :- Control unit device directs and coordinates the activities of
the entire computer which includes controlling the input/output devices or
units ,the operation of ALU and the transfer data to main memory . An
important function of C.U is program execution , fetching an instruction from
memory , decoding it and sending it to an appropriate place in the computer
to get it executed .
7. (b) Arithmetic logic unit(A.L.U) :- The arithmetic logical operation unit performs arithmetic
operation, the operands are brought to ALU from the memory . In ALU the required operation is
done and the result is sent back to memory for storage ALU . All these happens under the
control unit . ALU also perform comparison which are called logical operation, these occurs
when the operation are connected with logical operation .
LOGICAL OPERATION SYMBOL
EQUAL TO =
LESS THAN <
GREATOR THAN >
(c ) Memory unit :- The data and instructions that are entered into the system has to be stored
inside the computer before the actual processing takes place . Similarly the final results
produced by the computer also has to be stored before they are passed to the output units .
3. Output unit :- The data passed through the C.P.U can be viewed with the
help of output device ,the monitor or (VDU) of a PC is an output device.
8. The discovery of numbers, which is considered as the greatest
achievement of mankind led to the development of all kinds of
calculating device . Today we can’t imagine a work without
numbers , it took thousands of years to get the present system
of numbers .
The stone age man used pebbles for counting people or animals ,
stone was replaced by sticks on the rope .
9. The earliest and the simplest device that was used for
calculations was the ABACUS , simple abacus has been in use
since 3000 B.C.
Abacus was first developed in china and later its use spread to all
parts of the world .
10. The next manual calculating device logarithms was invented by
john Napier . The use of logarithms enabled him to transform
multiplication and division problems of addition and subtraction
. The word logarithms is a combination of two Greek words ,
logos (means ratio) and arithms (means numbers ).
12. Joseph jacquard
development in the early
19th century . Jacquard
was a textile
loom in 1804 . He used
punched card to produce
complex cloth pattern
with automated loom .
13. Charles Babbage , a
professor at Cambridge
university is considered
to be father of modern
digital computer . He
designed his “different
engine” in 1822 and his
“analytical engine” in
14. In 1855 , Herman
Hollerith , developed a
machine run on the
electricity for the first
time for calculating and
recording data . It was
capable of reading both
numbers and letters ,
processing and giving
out letters and numbers
in designed form .
C.U.I . Ex ;
G.U.I . Ex ; windows xp interpreter B.I.O.S
16. 1. Computer: It is an high speed electronic device which is capable of performing
logical and arithmetical operation .
2. Software : It is set or series of instruction given by user is known as program ,
the instruction is written in one of many language when the computer can
understand and are called the programming language . All the computer programs
written in any programming language are collectively known as software .
3. System Software : It is a collection of programs designed to operate , control and
extend the processing capabilities of computer . It can be classified further into
three parts .
Language translator :- A software that convert source codes into machine case
vice-versa are called language translator .
(a) Interpreter :- It is a program written in machine level language whose function is
to translate the high level program into the machine level language .
(b) Compiler :- Compiler will check the program at a time and display all the errors.
(c) Assembler :- It is a program written in assembly level language whose function is
to translate the assembly level program into the machine level program ..
17. Operating system :- A collection of programs and utilities that provide a basic
working environment for other software application and computer user . It provide
a platform where all the application software runs .
EX : MS-DOS , UNIX , WINDOWS , etc .
Classification of operating system .
(a) Single program/user o.s :- It permit one application or program to be run at a
time , when the processor (C.P.U) of a computer does one job at a time .
(b) Multi user o.s :- It permit numbers of application of user to work at the
computer at the same time . Ex : LINUX,UNIX.
(c) Graphical user interface :- It uses icons or small images to represent program
features instead of typing (or) entering the command . Ex: window 95 , 98,2000 etc
(d) virtual storage o.s :- It is originally devised , when the programs that were too
large to fit in primary memory i.e. RAM . A visual storage operating system will
permit data to be moved between primary & secondary as and when the primary
storage proves to be too small .
Utility :- These are the programs , pre-written by the manufactures and supplied
with hardware . Ex: text editor , sorting , formatting , etc .
18. Generation of computer : The term generation refers
to major development in electronic data processing .
Computer technology has been aimed at making
smaller cheaper and efficient computers. The
development of computer has been very rapidly in last
fifty years . It has been in five distinct stages . Each of
these stage is called generation .
19. The first generation
computer is based on
the vacuum tube technology . In
the first generation some
important computers that
were designed are as
20. ENIAC (electronic numerical and calculator ) :- In 1946,
Mauchly and Eckert completed the first large scale electronic
digital computer ENIAC . The ENIAC was programmed by
connecting wires between units of the computer and setting
switches at the 50 feet . It was used for , atomic energy calculation
and random numbers studies .
EDSAC :- After ENIAC was turned off , another computer EDSAC (
electronic delay storage automatic calculator) came in 1943.
EDSAC was first computer to operate on the stored program
concept . It started operating only in 1951 . ENIAC, EDSAC and
other computer which were developed in 1940’s were experimental
UNIVAC :- UNIVAC ( universal automatic computer) was the first
computer dedicated to business application . It was also used for
the analysis of 1952 presidential election in united states.
21. Drawback :
First generation computer based on vacuum tubes
created several problem
It generates too much heat .
It consumed lots of electricity.
Its, size was large , unreliable and required constant
The computer programming language was in binary
digit (0,1) which have a special meaning that can be
understood by computer .
It was very difficult to write program in machine
language , moreover most program contained errors
and the knowledge was restricted to few people .
22. Major innovation was the solid
state device – transistor by three
scientist J.BARDEEN , H.W
BRATTIAN and W.SHOCKLEY
A transistor is made of a semi
conductor material whose basic
part is silicon
The size of transistor is only
1/200th of the size of vacuum
Require much less power and
produce less heat .
Ex : IBM 7094,NCR 304, IBM 1620, ALTA’S etc .
23. Integrated circuit technology was
introduced around 1965.
It is the combination of numbers of
transistors and other electronic
components fused together on a
Mass storage device were called
auxiliary or secondary storage
device i.e. magnetic tape , disk ,
Multi – programming software in
which more than one can be
present in computer memory
High level language like basic
COBOL, FORTAN , etc , were
A new computer industry called
software industry was born .
Ex: IBM -360, ICL-1900,PDP-8, IBM-370/168 , etc .
24. A new technology Micro-processors
were introduced .
A microprocessor chip
(approx 1/4”*2” in size)
contain an entire central
processing units on single
Large scale integration
(L.S.I) and very large
scale integration (V.L.S.I)
technology were used in
fourth generation .
Size and cost reduced .
Desktop came into the
25. Ultra large scale technology (U.L.S.I) were introduced
Developed very small but extremely fast and powerful
computers which is known as ROBOTS .
Size were very much reduced .
Small in size and easy to carry out .
Ex: mainframe , super computer , ROBOTS .
26. The device which is used to input information or instruction into the computer are called input
device . Below are given a few input devices:
KEYBOARD: Allows user to interact directly , it resembles an electronic type writer keyboard
, available in two main category ;
(a) Standard with usually 83-84 keys .
(b) Enhanced or extended with 101 keys .
It is divided into 4 main parts .
1. Main pad.
2. Function key pad .
3. Numeric key pad.
4. Special key pad.
27. MICR : Magnetic ink character reader is basically used in banking industry to read
28. OCR : Optical character reader is capable of reading any printed or hand written
text they can read at the rate 2400.
29. OMR : Optical mark reader can recognize marks made by pencil or ink on
specially designed paper with boxes which can be marked with a dark pencil or
30. BCR: Bar code reader used to indentify a particular product written in bar or
shops over the product , ex: books , packages etc .
31. MOUSE : An electro- mechanical device used as pointer to select items from an
“ on screen” menu.
32. SCANNER : The scanner is used to scan images and store it on the disk as a file ,
it can be flat bed or roller feed variety .
33. LIGHT PEN : It is a
pointing device which
can be used to select
an option by simply
printing at it ,or draw
figure directly on the
screen and more
figures around .
34. TOUCH SCREEN : Normally used when information has to be assessed with
minimum effort , the screen is made sensitive to touch and exact position is
detected . The screen is lined with light emitting device ( LED ) . It is used in
hospitals , railways , air lines , restaurant , stock exchanges , etc .
35. JOYSTICK : It is mainly used with computer games , and it some times called game
controller . It can be moved left and right (or) up and down as required to move the
36. The input received is processed in the processing unit and when the result are ready , are given inform of
output . The device through which these output are given are known as output device . Below are some
commonly used output devices .
The most commonly used output device is the visual display unit (V.D.U ) , which is used to display
information on the screen the V.D.U. consists of a CRT ( cathode ray tube ) which produces a beam of
electrons that make the picture on the screen . A VDU normally consist of 25 rows an 80 columns . It has 200
pixels from top to bottom and 640 pixels from left to right .
37. Popularly monitors are :
o Monochrome :- These types of monitors have single foreground colures
and single background color but have various attribute . Ex; the
brightness and intensity of character which can be changed .
o C.G.A ( color graphic adapter ) :- Introduce by IBM in 1982, these monitors are
of low resolution screen (640 row*200 columns) with color
o H.G.A. ( Hercules graphic adapter ) :- Introduced by Hercules computer
technology in 1982 , these are monochrome adapter with additional
graphic display mode which provide high resolution in graphic mode
(750*350 dots )
o E.G.A. ( Enhanced graphic ) :- Introduced by I.B.M in 1984 , it was developed
in an effort to unify the variety of display adapter . The E.G.A
combines all of the features of other adapter an d provide high
resolution using higher quality color monitor . It support 16 colors .
38. o V.G.A ( video graphic adapter ) :- Introduced by I.B.M in 1987 , these monitors support higher resolution
and are very expensive . It can support 256 color at a time .
o Super V.G.A:- Introduced by a group of American companies in 1988 , it uses more pixels (56.1)
more than V.G.A.
39. PRINTER :-
A hardware device that produces text or
graphics output on a paper , printer are
grouped broadly into either impact or non-impact
Impact printer :
These printer have mechanical contact
with print medium ( usually paper ) to create
an image ( Dot matrix , line printer , daisy
wheel printer )
Non – impact printer :
Those printer that not have direct contact
with the print medium fall under this
category ( inkjet printer , laser printer ).
40. PLOTTER :-
A printer is capable of producing output that contains printed words . It is capable of printing
straight lines and simple figure like squares , rectangles and circles . It require to create high
quality visual on papers , which a printer a printer is not capable of doing . For this purpose ,
at plotter is used .
A plotter is a printer that is used to create
presentation , charts , graphics , maps , and diagram prepared for statically application like
CAD ( computer added design ) , engineering drawing etc .
41. This memory is directly associated with the C.P.U. before being actually processing the data , this is to be
stored in some storage area . This storage area is known as primary storage .
It is divided into two distinct parts:-
I. RAM and ii. ROM
RAM :- Random access memory where all data will be stored , while typing anything it directly
stores in electronic circuit and it works continuously till power continues . It goes through reading
procedure from input device to RAM and it writes from RAM to secondary device like floppy/ hard
ROM :- Read only memory basic startup routines and Bios ( basic input output system ) are
permanently loaded during the manufacturing time . It can’t be altered and fresh information
cannot be written into a ROM .
So, if the power is off computer does not lost it’s contents .
It has three parts :
(a) PROM ( programmable read only memory ) :- Once the chip has programmed the recorded
information can’t be changed .
(b) EPROM(erasable programmable read only memory) :- It can be performed or reprogrammed ,
usually by exposing a normally covered sector to ultra –violet light , information can be only
“read” and the information remains on the chip until it is erased .
(c) EEPROM ( electronically erasable programmable ROM ) :- RAM can not store memory between
power interruptions , and hard disk are slow . Enter flash memory , it does not lose it’s data even
if the power is turned off . A flash memory is used in portable device such as digital camera ,
voices , recorders and handled computer .
42. Cache memory :-
These are small but fast memory logically positioned between the internal and main memory .
It stores or catches some of the content of the main memory , currently in use by the processor
. Being nearer to the C.P.U. than the RAM it plays a major role in the speed and performance
of a processor’s (CPU). To make the processor job easier and quick , the cache memory stores
anticipated instruction . The size of cache memory being very small . Whenever a CPU
requires data , it checks with the cache and if available , directly uses the same . Currently PCs
normally features two of cache , L1 or primary cache located in the CPU itself and L2 or
secondary cache located on system ‘s motherboard .
43. For permanent storage of data , secondary device can be used with a p.c. system .
Secondary storage is also referred to as external storage .
(A) MAGNETIC TAPES: These storage device are used to keep back-up copies of
previous software and data .
44. (B) FLOPPY DISK : IT was developed in 1970’s as a cheaper and faster
storage device .it is small random access disk .
45. (c) HARD DISK : Another
magnetic media suitable
for strong large volume
of information is the hard
disk . A hard disk pack
contains two or more
magnetic plates fixed to
a spindles one below the
other with a set of
46. (D) CD-ROM :- Compact
disk read only memory is
an optical storage
medium capable of
holding up to 660 MB
data ( approx 500,000)
range of text about 70
minute of high fidelity
audio or a combination of
the two .
47. (E) ZIP DRIVE : A zip
drive , which used a
removable disk cartridge
, can be used for
backups . It can typically
stores 100 MB or move
on each removable
cartridge . The
advantage of this device
is that it is random
access just like a disk
48. (F) DVD- ROM : THE CD-ROM
is going to obsolete
very soon after arrival of
DVD-ROM in the market
for DC-users , it has
several time higher
speed and capacity of
CD-ROM very soon . It
will be counted as most
common device name
CD-ROM . The full form
of DVD-ROM is Digital
video disk read only