This document provides information on the history and generations of computers. It discusses: - The first generation of computers used vacuum tubes and were very large, requiring high maintenance with limited storage. - The second generation introduced transistors, making computers smaller, more reliable and increasing storage and speeds. - The third generation used integrated circuits, further reducing size and increasing speeds and reliability. Storage increased to 128K and various I/O devices were developed. - The fourth generation began using microprocessors, making computers much smaller, faster and cheaper with larger storage capacities. Personal computers became widely available. - The fifth generation aims to develop natural language processing, parallel processing and artificial intelligence capabilities.

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UNIT-1
COMPUTER
C  for calculate
O  for operate
M  for memorize
P  for print
U  for update
T  for tabulate
E  for edit
R  for response
Computer is a high speed electronic data processing machine.
In other word we can say that computer is a machine that
can accept data prowess. It according to stored a program of
instructions any give the result.
OR
Computer is an electronic machine which takes in the
information & does the processing at a much faster speed perhaps
beyond the of human resulting out an accurate & error free output.
OR
Computer is an electronic machine which takes In data
process it according to instruction give to it by performing some
arithmetical & logical operations & giving out the result as a
much faster speed then human being.
CHARACTERISTIC OF COMPUTER
1. The ability to perform calculation at a fast speed.
2. The ability to take in information & to store that
information for future retrieval.
3. The ability to take in & to store a small variety of
instructions for execution.
4. The ability to use simple logical rules to make decisions
for their own internal control or for the control of some
external activity.
5. The ability to communicate with other computer systems.
6. To carry out computations & analysis accurately and
speedily.

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ACCURACY
Computer give consistently accurate results. The accuracy
does not go down even when they are used continuously for days
together. However, the accuracy will depend on the method of
programming & the way of result are interpreted. The accuracy also
depends on the type of machine you employ. For example a
microcomputer may give accuracy up to32 decimal places.
DATA
Data can be defined as fact related to people, places,
event or things. Which can be represented using number and letters?
Eg. : Name, age etc.
HISTORY OF COMPUTER
In present time the history of computer (super) dates
back to 353 year. In 1642 a French mathematician Mr. Blaze Pascal
invented a mechanical calculate machine. This machine was based on
gears& levers. Which could subtraction or addition the figures. It
was named as “pascaline”. Approximately at the same time a German
philosopher Goth fried. Von Leibniz invented a similar device.
These machines ware widely used in offices. There after about 150
years, an English mathematician “CHARLES BABBAGE” invented a
machine in 1833. Which was named as “the Babbage difference
machine” & with this the hope for modern computers invented. There
after in 1879 a scientist named Hallerith invented another machine.
Which came to be known as “Gensus Tabulator”. This machine they
used punched card by the year 1911 many other companies immolated
in the above company. Hollerith named this company as “computer
tabulating recording” & by 1930 IBM marketed 80% punched card.
Slowly the electrical equipments changed. In 1939 a scientist named
Harward Aiken of Harward Aiken of Harward University invented a
machine named “Sequence Controlled Calculator”. This was sub
sequentially known as Mark Ist . This machine was got ready in 1944.
Five hundred meal electrical wire & 30 lacks Electrical Connections
were used to manufacturer this machine when we calculated any two
numbers through this machine we got the response with in six
seconds, similarly in the case of division the response came with
in twelve seconds. Charles Babbage is known as father of computer.
GENERATION OF COMPUTER
The growth of computer generation after the end of world
war IInd was very rapid but this development took in five district
phases known as computer generation.
First generation (1940 to 1955)
Second generation (1955 to 1964)
Third generation (1965 to 1972)
Fourth generation (1972 to 1984)
Fifth generation (1984 to …………….)

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FIRST GENERATION
The first generation of computer are these in which
vacuum tube are used magnetic tape device & magnetic core
memory(ies), where develop during this period.
ENIAC (Electronic Numerical Integrator And Calculator)
This was built in the year 1946 by J.P. Eckert & J.W
Mauchly at the University of Pennsylvania (USA).
EDSAC
( Electronic Delayed Storage Automatic Computer)
This was built in the year 1949 at Cambridge University
This was the first electronic computer which could store
instructions
EDVAC
(Electronic Discrete Variable Automatic Computer)
It was make in 1950 this was made at the university of
pennsvlvanis
UNIVAC
(Universal Automatic Computer)
It was made by Eckert & mouchly who ha set up a company
of their own. This was made in early 1951.
IBM
(International Business Machine)
It was developed Ibm-650to computer market of Univac. It
was an expensive machine.which was accepted widely & gave IBM the
status of the market leader in computers.
LEO
(Lyons Electronic Office)
THE CHARACTERISTIC OF THE MACHINE
1. The machines were very large.
2. Required high maintenance.
3. Had limited storage facility.
4. Used machine language for instructions.
5. I/O speed was low.
6. Access time was 10 sec or mille second.
7. Were more suitable for scientific computing rather
than administrative applications.
SECOND GENERATION:
The second generation computer were marked by the use of
a solid stop device called the transistor. In the place vacuum tube
all those mechanic were must faster more reliable then their
earlier computer of part.
OR

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The second generation began to appear in the year
1975.John barden William Shockley & walter brattam, working at bell
laboratories had developed transistor in the year 1948.
THE FEATURE OF SECOND GENERATION
1. The hardware size reduces.
2. Increased reliability.
3. The internal storage was increased (1.4 K to 16K)
4. Access time is 10-5 second or 10 micro second.
5. The I/O & computational speed was increased.
6. The system was used for administrative & scientific purpose.
THIRD GENERATION
In the field of the electronics led to the innovation of
the integrated circuit, those circuits ware known as I.C. chips the
use of IC chips in the place of transistor gave but to the third
generation computer.
OR
The third generation computers used IC’s for CPU
components. In the beginning third generation computers used
magnetic core memory, but letter on semiconductor memory(ies) (RAM
& ROM) were used. Semiconductor memories were LSI chips. Magnetic
disks, drums, & tapes were used as secondary memories. Cache memory
was also incorporated in the computer of third generation.
Microprogramming parallel processing (pipelining, multiprocessor
system etc). Multiprocessing, multi-programming, multi user system
(time share system) were just introduced. The concept of virtual
memory was also introduced.]
THE FEATURE OF THIRD GENERATION
1. There was a reduction the computer size.
2. Each IC’s replaced hundreds of transistor.
3. Internal storage capacity was further increase (16k to 128).
4. There was a marked increase in the computational & the I/O
operations speeds.
5. A number of I/O device were developed.
6. Higher level languages were used for instructions.
7. Higher system became more reliable.
8. Access time is 10-7 sec or 100 nano sec.
9. The secondary storage were introduced which cheap & had
high storage capacity.
10. IBM-360, ICL-1900, IBM-750, ICL-2900.

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FOURTH GENERATION:
In the year 1975, microprocessor became popular. A
microprocessor could replace hundreds of IC’s. This led to further
reduction in the reduction of computer.
APPLE’S by the end of 1977, APPLE2nd & TRS-80 of Tandy
Corporation were the popular brands, computers became smaller in
size & leaser in caste.
IC’s which have the entire computer circuitry on a single
silicon chip are called MICRO-PROCESSOR. The computers using these
chips are called micro-computers or short micros.
Altair was the first micro computer designed by Ed
Roberts, President of MITS, This was based on modify version of
INTEL 8008 Micro-processor chips, known as 8008.
The first pocket computer (not calculator)was a japans
make solid in year 1980. It is called sharp 1211.
The apple series of micro-computer was developed by Steve
Woznak & Steve Jobs in 1976.
APPLE 2nd known as personal computers is available for
only few thousand rupees. The personal computer developed by the
multinational giant IBM in 1984 used 16 bit micro processor are
belong to fourth generation of computer.
THE CHARACTERISTIC OF FOURTH GENERATIONS
1. Size reduced considerable.
2. Very high speed.
3. Large storage capacity.
4. Very high reliability.
5. Low cost.
FIFTH GENERATIONS-1985
This generation of computers were much more strong &
modern then the old ones. The IBM 80286, 386, 486, 586 etc are
being to the generation of computer & the development of the super
computer was possible in this generations. In this generation a new
technique was developed in computer & which called “ROBOTKS”.
A part from the above there were wide change in software
also that is software with artificial intelligence were developed
during this period & new operating system were marked in the field
of application software. Windows-95 is the best example of this. We
can increase the memory (RAM) according to our need. IDE & SCANGI
HARD DISK are also developed in this generation & it became
possible to store data.
KIPS Kilo/Knowledge Information processing system.
C-DAC PUNE (INDIA) developed “super computer” “PARAM” in
India. This was the latest type of “Tera Flop Super Computer” So
for only AMERICAN & JAPAN had processing per second so that India’s

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recently developed “PARAM” will be all tera Flop & “PARAM” 9000
will be 2 Giga flop which can be increased to 32 Giga flop.
In the fifth generation of computer have talking
understand & picture understanding. It is 10 to 100 times more
effective than the computer of the 4th generation.
THE CHARACTERISTIC OF FIFTH GENERATIONS
1. Natural language processing system.
2. Processing non-numeric picture and graphs.
3. Technology used parallel processing and VVLSI.
4. Incorporated Artificial Intelligence(AI).
TYPES OF SCHEDULER
There are two types of scheduler –
1. Primitive
2. Non primitive
PRIMITIVE
In primitive scheduling the CPU can be taken away by the
allocated process. Primitive scheduling is more useful in high
printing, which requires immediate response.
NON PRIMITIVE
If once processes has been given the CPU & the CPU can
not be taken from the scheduling is called non primitive. In this
type of scheduling the job are made to wait by longer job but the
treatment of all process is fairer.
MULTIMEDIA
It is a very powerful means of importing information.
Multimedia is throw are view using number of medium together. Those
mediums can be text, voice moving image, still image, audio, video,
sound etc.
MULTIMEDIA COMPONENT
1. The text can be used for additional emphasis.
2. Graphics provide a visual impact. It is generally said that
a picture.
3. Is worth a thousand words. Thus graphics can be used for
enhancing a presentation.
4. Voice trees to enhance a presentation to the extent that a
presentation moves on to form of persuasion. Many people
want to listen about a particular topic rather than reading
about it.
5. The animation can be used effectively for attracting
attention. Animation also make a presentation light, thus
can be used for presentation of several complex subjects.
It is also a tool which help in focusing attention.

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6. The video part of multimedia can be used as a powerful
communication providing clear cut instructions.
DEVICES
There are two types of devices
(I) Input Device (II) Output device
INPUT DEVICE
Input device are many types but basically. They used for
presenting the data to the computer in machine readable form same
of the input device as following …….
1. Punched Card
2. Punched Card Reader
3. Key Board
4. Magnetic Tape
5. Magnetic Disk
6. Magnetic Disk Drive
7. Floppy Disk
8. Floppy Disk Drive
9. Mouse
10. Light Pen
11. MICR
12. MSR
13. OMR
14. OCR
15. Joystick
16. Trackball
17. Graphic Tablet
18. Touch Screen
19. Scanner
20. Web Camera
21. Card Reader
22. Video Camera
23. Bar Code Reader
24. Micro Phone
25. Smart Card Reader
26. Biometric Sensors
27. Digital Camera
28. Bluetooth
29. Floppy
30. Compact disk(cd rw dvd rw)
31. Pen Drive
32. Memory Card
KEY BOARD
A keyboard is similar to the keyboard of a typewriter. It
contains alphabets, digit, special character, function keys & some
control keys. When a key is passed electronic signal is produced

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which detected by an electronic circuit called keyboard encoder.
There are different kinds of key board
(I) Normal Keyboard
(II) Multimedia Keyboard
LIGHT PEN
A light pen is used to select a displayed menu option on
the screen when its tips touch the screen.
MOUSE
A mouse is also a pointing device. It is held in one hand
& moved across a flat surface. The size of the mouse is about a
normal cake of bath soap. It usually rolls on a small rubber ball
and has two or three buttons on the top. When the user rolls the
mouse across the flat surface the cursor on the screen moves in the
direction of movement, giving the user a sense of pointing at
something on screen. There are different kinds of mouse
(I) Mechanical Mouse
(II) Opto-mechanical mouse
(III) Optical Mouse
(IV) Wireless Mouse
TOUCH SCREEN
In touch screens, a grid of light beams or fine wires
criss-cross the compile screen, when you touch the screen with your
finger, the rays are blocked and the computer senses where you have
pressed and thereby identifies the object which you want to choose.
Mostly touch screen are used to choose options, which are
displayed on screen. As touch screen are very easy to use, they are
often used as input devices in public places such as ATM, Airports,
Travel Agencies etc.
JOYSTICK
A joystick is also a pointing device. It is used to move
the cursor position on a monitor screen its function is similar to
that of mouse & is used for playing games.
TRACK BALL
A trackball is also a pointing device & contains a ball
which can rotate in any direction. The user spin the ball in
different directions to move the cursor on the monitor. The
associated electronic circuitry detects the direction & speed of
the spin. The information sent to the processor. This type of
pointing device is normally used in a laptop computer.

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GRAPHIC TABLET
A graphic tablet or simply a tablet or digitizing tablet
is an input device that enables you to enter drawing and sketches
into a computer. A digitizing tablet consist of an electronic
surface and a cursor or pen. A cursor is a similar to a mouse,
except that it has a window with cross hairs for pin point
placement and it can have as many as 16 buttons. A pen(also called
stylus) look like a simple bal point pen but uses an electronic
head instead of ink. The tablet contains electronic circuitry that
enables it to detect movement of the cursor or pen and translates
the movements into digital that it sends to the computer.
A graphic tablet has flat pen(called the tablet) on which
you can draw with a special pen(called stylus) or with a special
device (called puck). As you draw on the pad, the image is created
on the screen. The drawing created in this manner are very accurate
(generally up to 100th of an inch).
SCANNER
Scanners are a kind of input devices. They are capable of
entering information directly into the computer. The main advantage
of direct entry of information is that users do no have to type the
information. This provides faster & more accurate data entry.
CARD READER
A card reader is a peripheral device that reads punched
cards. A punched card is a storage medium made of thick paper card
that hold data in the form of punched holes. The holes are punched
into the card by a keypunch machine or card punch peripheral device
connected to a computer.
The punched card code I detected patterns of light
streaming through the holes in the cards. Another card reader
called magnetic cared reader is used for reading the magnetic strip
on the back of credit cards & is used for transferring data sent
through the card.
WEB CAMERA
A web camera is a camera that takes to accept into just
by focusing on an object. The camera is focused on the input object
to take a picture of the object. Picture so taken can be
transferred over network to a distant place. Thus two or more
persons can take Y see one another in this way. This method is
used in video conferencing.
VIDEO CAMERA:
A video camera is a camera that takes continuous pictures
& generates a single for display on a monitor or for permanent
recording. Singles generated by video cameras are traditionally

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analog, but now a days digital video cameras are available. The
latter coverts analog signals into digital form.
Bar code reader
It is also one of the most widely used input devices. As you must
be aware that a bar code is a pattern of printed bars on various
types of products. You may even see a bar code printed at the back
cover of this book. A bar code reader emits a beam of light
(generally a laser beam) which reflects of the bar code image. A
light-sensitive detector in the bar code reader then identifies the
bar code image by recognizing special bars at the both ends of the
image. Once the bar code is identified, the bar pattern is
converted into a numeric code that can be processed later in any
manner.
MICR (Magnetic Ink Character Recognizer)
This computer can recognize character written in special
ink. This ink contain magnetic particles & that is why MICR is able
to read them. The character of MICR is that it , can read only
character with special construction. This is getting popular in
Bank & is used in dealing with cheques.
MSR (Mark Sense Reader)
This is a device which fan read pencil/ink character on a
special type of card & card & form such cards & farms are pre pared
in such a way that every character has a different meaning. This
device is used in examination surveys etc.
OMR (Optical Mark Reader)
This device can read & count any work printed or made by
hand. These days the valuation of the o0bjedtive type examination
book are evaluated by this method.
OCR(OPTICAL CHARACTER READER)
An optical character reader is used to read character of
special type font(s) printed on conventional paper with
conventional ink. These days, OCRs are capable of reading /
identifying hand written text also.
FLOPPY DISK
5” or 3.5” or BOTH TYPES OF FLOPY DISK DRIVE PRESENT ON
THE COMPUTER. The floppy disk drive is use for data storing or for
getting on the screen. For each computer a groove present in the
front part of the computer. Which insert the floppy for read or
work.
HARD DISK
Where as the question of hard disk drive there drives are
machine which made by very complicated, & micro type of parts.
These disk are made by metal. These are coated in both side. With

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the thin layer of magnetic matter. There are two heads are present
in the hard disk drive. Which are used for reading & writing in
side of hard disk the place where the information is write. It is
called FAT
FAT- File Allocation Table
OPTICAL DISK (CD ROM)
There became start of optical disk with the development
of laser technique. A very great amount of storage data can keep in
the disk this is known as CD_ROM. This is two types……….
1. Readable
2. Write & readable
We can read only of storage data in first type of
optical disk. We can read & write both to storage in second type of
optical disk. The optical disk which is available at the present
time. They can store 700 Mb data at a time.
CD_ROM means compact disk read only memory. It was
invented by PHILIPS company in 1974. this company was established
in 1890. In starting it manufactured carbon phi lament bulb.
In starting CD-ROM was known as LASER DISK & its size was
12” now it is manufactures by soni & Philips companies (starting
from 1982) its bade is 120’mm.
MICROPHONE
With more and more acceptability of computer in our
lives, sound capabilities or becoming a standards part of computer.
We can send sound input to computer through a special input devices
called microphone or mic in short.
SMART CARD READER
You are familiar with ATM cards that are used in ATM
machines., these cards store data through magnetic stripes on the
back of these cards magnetic stripes contain much more data per
unit of space than do printed characters or barcodes. Moreover, as
they can not be read visually, they are ideal for storing
confidential data. To read such cares, special reader machine s
are required, which can decode data on these magnetic stripes.
BIOMETRIC SENSORS
Biometric sensors are the input devices used for
identifying a person’s identify. Biometrics is a technology that
verifies a persons identity by measuring a unique-to-the-individual
biological trait. Biometric technologies include dynamic signature
verification retinal / irisscanning, DNA identification, face-shape
recognition, voice recognition and fingerprint identification.
Biometric identification is superior to lower technology
identification methods in common use today-namely passwords, PIN
numbers, key-cards and smartcards.

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Such as DNA, iris/retina patterns, face shape,, and
fingerprints- or measuring unique behavioral actions, such as voice
patterns and dynamic signature verification.
DIGITAL CAMERA
A camera that store images digitally rather than
recording them on film is called digital camera. Once picture has
been taken it can be downloaded to a computer system and then
manipulated with a graphic programs and printed. The big advantage
of the digital cameras is that making photos is both inexpensive
and fast because there is no film processing.
Digital camera differs from web camera in the sense that
it can be operated upon without a computer system where as a web
camera works with a computer system.
OUT PUT
Out put communication the information users inform under
stable to the human being out put device are many types same of the
device……
1. VDU OR Monitor
2. Card puncher
3. Printer
a. Character printer
b. Line printer
c. Daisywheel printer
d. Laser printer
4. Displayed output
5. Graphic output
6. Film output
7. Voice output
8. Speaker
9. Bluetooth
10. Floppy
11. Compact disk(cd rw dvd rw)
12. Pen Drive
13. Memory Card
14. Plotter
It can be classified in many ways ……
According to bed shape
1. Flat bed
2. Drum type
According to size of paper
1. A0 size (36* 44 inches)
2. A1 size (22*36 inches)
3. A2 size (1118 inches)
VDU OR MONITOR

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Monitor is the most common form of output from a
computer. It displayed information in a similar way to that shown
on a television screen. The picture on a monitor is made up of
thousand of tiny colored dots card pixels. The quality and details
of the picture on a monitor depends on the number of pixel that it
can displays. Different kinds of monitors
(I) CRT(Cathode rays Tube)
(II) LCD/Tft(Liquid Crystal Display/Thin Film Transistor)
PRINTER
Printers are commonly used output devices. They produce
printed output of results, programs & data. Printers are classified
into two major categories.
1. Impact printer
2. Non-impact printer
IMPACT PRINTER
Impact printers use electromechanical mechanism that
causes hammers or pins to strike against a ribbon & paper to print
the text.
DOT MATRIX PRINTER
This printer prints very fast speed & its doe’s works has
a high quality printer for general matter. In which fixed in a
head. In which fixed on 9 or 24 pins which that strike on the
ribbons for prints, besides this is prints two types…
1. Draft mode
2. NLQ (near latter quality)
DAISY WHEEL PRINTER
It is an impact type letter quality printer. It is used
where good quality printing is needed. The daisy wheel printer is
so named because the print head resembles a daisy flower with the
printing arms appearing like petals of the flower. The hub is
continuously rotating at high speed, and a hammer strokes the
appropriate character when it is in position. The printing element
is also changeable and variety of different styles are available.
The speed is in the range of 20 to 90 cps. It is costlier than DMP.
It can not print graphics.
DRUM PRINTER
A drum printer uses a rapidly rotation drum which
contains a complete set of raised characters in each band around
the cylinder. Each character position along the test line contains
a band of raided character set. There is a magnetically driven
hammer in each character position of the line. The printer receives
all character to printed in one line of the text form the
processor. The hammers hit the ribbon & paper against the desired
character on the drum when it comes in the printing position. Its

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nose level is high. Its speed varies from 200 to 2000 lines per
minute.
CHAIN PRINTER
A chain printer uses a rapidly rotating chain which is
called print chain. The print chain contains characters. Each link
of the chain is a character font. Magnetically driven hammers are
located in each print position. The printer receives all the
characters to be printed in one line form the processor. The
printer prints one line from the processor. The printer prints one
line at a time. A chain may contain more than one character set.
BAND PRINTER
Band printer is just like a chain printer. It contains
fast rotating steel print bands in place of chains. The print vane
contains a raided character set. Hammers strikes the ribbon & the
paper against the character to print the character. Some printers
can print up to 3000 line/min.
NON IMPACT PRINTER
Usually, a non impact type printer is faster than an
impact type printer. The disadvantage of non-impact type printer is
that they produce single copy of the text whereas impact printers
can produce multiple copies of the text. They use thermal,
chemical, electrostatic, laser beam or inkjet technology for
printing the text.
INK JET PRINTER
In this printer the print head works as a spray gun. The
print the character with spray on the paper. It is also best
quality of printing. It has speed of 40 to 300 cps with software
controls on size and style of characters. These printers support
color printing and very quiet and noiseless in operation.
LASER PRINTER
Laser printers are non-impact printers. They print one
page at a time. These printers use laser or other light source to
produce an image on a photosensitive drum. The computer controls
the laser beam to turn it on and off when it is cut back and forth
across the drum. The laser exposed areas attract toner. There after
the drum transfers the toner to the paper. The paper then moves the
a fusing station where the toner is permanently pasted on the
paper with heat oar pressure. After this the drum is discharged and
cleaned. Now the drum is ready for processing the next information
on the page. It produces a high quality output.
PLOTTER
There are using many high quality(ies) software in
present time, keeping in view the high quality of software, the

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printer became developed. They are print the natural & colorful
quality printing. This plotter is use AUTOCAD or in those
software, which are same as SUTOCARD. At the present time in using
two types of plotter……
1. Flat Bed Electrical Printer(plotter)
2. Drum Pen Plotter
FLAT BED ELECRRICAL PRINTER (PLOTTER)
From this of plotter we can take the high quality
printing. In working side they are same as electronic printer &
this is do work in simply & fast speed , in visual it has to see as
like a photo state machine or LASER.
DRUM PLOTTER
At the present tome the plotter of this series is used
very much. In seeing it function as a mechanical machine. Which is
use this pen its pens function very fast speed. In which use the
“fiver tiped” pen, it is very costly, the maintenance is very high
& costly of this plotter.
SPEAKER
As the sound capabilities have become a standard part of
a computer system, speaker have become key sound – output system. A
computer system having sound capability can not work without a
sound card. Speakers received the sound from a electric current
from the sound card and then convert it to sound format.
SPEECH SYNTHESIZER
Speech synthesizer is an output device that converts
textual data into spoken sentences. To produce the speech, basic
sound units called phonemes are combined. The sequence of words in
a text are combined into phonemes, amplified and outputted through
a speaker attached to a computer.
Speech synthesizers find wide application in treating
blind or dumb people. Text information can be read out to the blind
people using the speech synthesizer. Also a dumb person can type
the information he wants to convey & the speech synthesizer will
convert it into spoken words.
WINCHESTER DISK
The Winchester disk is a medium sized non-interchangeable
metal disk permanently housed in a sealed, contamination-free
container. The read/write heads are built in with the disk. These
disks are used with mini & personal computers only.

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CLASSIFICATION OF COMPUTER
Computer can classified on the basis of different factors
such as circuits & task performance capabilities. Computers have
been classified into three categories.
1. Analog computer
2. Digital computer
3. Hybrid computer
ANALOG COMPUTER
Analog computer operate by floppy disk mustering rather
than counting. The name which is device from the Greek word. Analog
denotes that the computer function by establishing similarities
between two quantities that are usually expressed as voltage or
current.
DIGITAL COMPUTER
Digital computer operate essentially by co8unting all
quantities are expressed as discreet digit or numbers. Digital are
useful for evaluating arithmetic expression & manipulation of data.
OR
Digital computer is a digital system that performs
various computational tasks. Digital computers use the binary
number system. Which has two digits i.e. 0 & 1? A binary digit is
called a bit. Information is represented in digital computer in-groups
of bits. It performs several different tasks & is
interactive in nature. If any error has been available in hybrid
and analog computers.
1. Digital computers convert data into digits.
2. It operates essentially on counting instead of
measuring.
3. It accepts information in the form of discrete pulses.
4. Used for business & scientific applications.
5. Interactive in nature.
6. Most popular & widely used computers.
HYBRID COMPUTER
The combination of analog & digital computer are known as
hybrid computer. These computers are mostly used with process
control equipment in continuous productions plants like oil
refineries etc. & used at places where signals as well as data are
to be entered into computers. Areas of application- nuclear power
plants, mine etc.
Classification of digital computer
1. Micro computer
2. Mini computer
3. Main frame computer
4. Super computer

17. Page 17 of 31
MICRO COMPUTER
This computer was developed in 1970 & was based on chip”
since this computer contained microprocessor, therefore it was
known as micro computer.
OR
The most common type of computer are micro computers
which is portable personal computer that fits on top of desk. It is
a small computer, mainly consists of single chips. Average data
transfer rate of microcomputer is 5 lack bytes per second. It can
hold from 8to 32 bit word length.
There are three varies..
1. PC (1981-84)
2. PC-AT (1985-)
3. PC-XT (1985-87)
PC (PERSONAL COMPUTER)
This computer was manufactured by IBM Company in 1981.
But in the begging they use only 8084-8087 microprocessor, 256kb
RAM & a floppy from 80 kb, 360kb(2d) & primary version of dos were
used. In this only limited quantity of software were used.
The size of floppy used to be 8.5 instead of 5.25 as at
present.
2. PC-AT (Personal Computer Advanced Technology)
The technique was developed in 1985. PC-AT was 16 bits
computer where as before its development only 8 bits computers had
been manufactured.
In the present days about 80% of the new computer are in
the market of PC-AT. At present the following modes of PC-AT are
available.
PC-AT 80286 12 MHz to 25 MHz
PC-AT 80386 25 MHz
PC-AT 80386 33 MHz+ 128 kb cache RAM
PC-AT 80386 dx 40 MHz+128 kb 512 kb cache RAM
PC-AT 80486 sx 40 MHz+ 128 kb 512 kb cache ram
PC-AT 80486 40 MHz +128 kb 512 kb cache ram
PC-AT 80486 dx 40 MHz +6 MHz 256 kb -512 cache ram
PCAT 804866 Pentium (66-900 MHz)
These computer are 16 to 64 bits of computers.
PC-XT (XTENDED TECHNOLOGY)
Pc-xt was invented after pc in this 8088 & microprocessor
were along with 1 Mb =40Mb of hard disk & 1mb =ram had been used
subsequently the technique was modified in which 1.2 Mb floppy disk
drive was used instead of 360 kb floppy & the use of double HDD /
FDD was made possible & use of bigger software was made possible.

18. Page 18 of 31
MINI COMPUTER
This computer are larger in size than microcomputers and
have a very fast processing speed. It consists of multiple
processing unites in a single chip . It uses word length of usually
16.24.32 or 64 bits. They can support up to 15 to 25 terminals
simultaneously. Some important mini computers are magnum vax mighty
frame.
MAINFRAME COMPUTER
These are very large machines with the capability of
parallel processing. The data transfer rate of this machine is 8
million bytes per second. It use the word length of usually
24.32.48 and 64 or 128 bits. Mainframe is used for centralized data
processing like train reservation, air reservation, main frame
computers can support over 50 terminals. Some important mainframe
computers are fdm3090, vax8842 etc. they are used by big business
concern & government initiations. These main frame computer can be
used by different people & for different purpose at the same time.
SUPER COMPUTER
Super computer Is the strongest computer amongst all
computer so for. It is being is very successfully in space science.
It is capable of calculation million of dates in second. It is
being used in high quality animation. It is cast less of all
computers.
OR
Super computer are much faster & more powe3rful than
mainframe computers. Their processing speed lies in the range of
400 MIPS 10000 MIPS. Word length 64-96 bit memory capacity 256 MB &
more. Hard disk capacity 1000MB & more & machine cycle time 4-6
nano-second (n.s). super computer are specially desi9gned to
maximize the number of flops. Their floating point instructions per
second (FLOPS) rating is usually more than 1 gigaflops per seconds.
Super computer contain a number of CPU’s which operate in
parallel to make it faster. They are used for massive data
processing and solving very sophisticated problems. They are used
for weather forecasting, weapons research & development, rocketing,
in aerodynamics, seismology, atomic, nuclear & plasma physics.
BUS SYSTEM
The whole computer system is made by the combination of
many units. These all units are add with join together. The all
data and instruction which in present in computer. These are runs
on circuit & cable seeing, cable are like a wire. Where circuit s
are like a micro electric wire. In the form of the circuit & wire
work outside of computer in the form of cable. They are divided
into three…….

19. Page 19 of 31
1. Data bus
2. Address bus
3. Control bus
DATA BUS
Data bus is that technique which is take data & transfer
from one place to another unit and returns the data from one unit
to another unit. It is bi-directional bus. Bi-directional means
data can travel in both directions.
ADDRESS BUS
The function of address bus is to send the information or
instruction to another bus.
CONTROL BUS
The function of control bus is to keep balance the whole
systems & to keep control the activity or processing of computer.
It all the operations in the CPU. The most common signals are read
& write signals.
MEMORY
1. Primary memory (semi conductor memory)
a. RAM [there are two types static RAM & dynamic
RAM]
This stands for random access memory. It is a read write
memory of a computer. In this type of memory any location can be
accessed in a random manner and the access time is same for each
memory location.
A lot of memory cells are contained in the chip. Each
cell contains group of bits that access together. The size of
memory data register (MDR). There are two types of ram.
1. Static ram
2. Dynamic ram
STATIC RAM
The information stored in this static RAM remains valid
as long power is applied to the unit it is costlier & consumes more
power. It is consists of internal flips-flops that store the binary
information.
DYNAMIC RAM
Information is stored in this DRAM in the form of
electric charges that are applied to its capacitors, the stored
changes on the capacitors tend to discharge with the time.
Refreshing the dynamic memory must periodically recharge it.
Cycling through the words refreshing. DRAM has reduced power
consumption & larger storage capacity in a single memory chip.
1.ROM
1.BIOPOLAR

20. Page 20 of 31
1.MROM 2. PROM 3. EROM 4. EEPROM
2.UNIPOLAR
2.SECONDARY MEMORY (MAGNETOC MEMORY)
ROM Read Only Memory
RAM Random Access Memory
MROM Masked ROM
PROM Programmable ROM
EROM Erasable ROM
EEPROM Electrically EROM
ROM
This is noting can be written on it. It is non-volatile.
The information stored in it is not lost when power goes off. It is
used for storing the bulk of the programs that are permanently
reside in the computer.
PROM
Its contents are decided by the programmer or user.
Permanent program & data are stored in a PROM.
EROM
It is exposing to high intensity short wave ultraviolet
light for about 20 minutes can erase the data stored in it. So it
is used to store permanents programs but need updating.
EEPROM
This clip can be erased & reprogrammed on the board
easily on a byte by byte basis.
CACHE MEMORY
This memory is placed between the CPU & main memory it is
a fast speed memory & expensive memory. It is used to store the
frequently accessed data of main memory. The instructions that are
less used by the CPU are stored in cache memory.
This memory is used to increase the speed of the system.
It improves its performance. From economical point of view the
capacity of the cache is much less than compared to main memory.
The procedure to access the cache memory. Is different from that
accessing the MAIN MEMORY, when CPU access the MAIN MEMEORY, the
cache memory compares the incoming address to address stored with
the data in cache. If it is found in the cache then there is “hit”
as occurred & corresponding data is read fro cache memory , in code
when address is not found in cache memory then there is a “miss”
has occurred & now the data is read from the main memory by the CPU

21. Page 21 of 31
& simultaneously stored in cache memory. When same address is
required nest time a “hit” may occur.
CISC & RISC (complex instruction set computing║ reduced instruction set computing)
It is a design of microprocessor. RICS are hardwired 20%
of the work & 80% of the work is implemented by computer software.
RISC machines are 5to 10 times faster than CISC machine.
CISC machine uses micro-programming. Highly complex
instructions arte generated with the help of micro-programs. CISC
machine are more complex & less efficient. Complex instructions
lead to a number of complications in both hardware & software
design.
1. 8 bits = 1byte
2. A character = 1 byte = 8 bits
3. 1 kilo bytes (KB) = 1024 bytes or 210 bytes
4. 1 megabytes (MB) = 1024 KB
5. 1 gigabytes (GB) = 1024 MB
If the capacity of memory is 16 MB means it contains
16*220 bytes or 224 bytes. A 1.44 MB floppy can store 1.44*220
bytes of information.
ALU (Algorithm Logical Unit/Arithmetic Logic Unit)
This is one of the most important part of the computer.
It has paid most active role in calculation & analysis work done by
computer. It obey the instruction of control unit. It connects the
memory unit after receiving the instructions from control unit &
gets the effective information. After getting the information it
does the processing as per control unit instructions.
C.U. (Control Unit)
C.U. as it is ape rant by its name regulated different
internal processing of computer. its primarily work to receive the
instruction from memory unit, to decode these instruction, &
according instruct, the remaining part of computer to do the
different kinds of processing, so that it works as a chain between
the different parts of computer, & transfers the information & data
as needed.
M.U. (MEMORY UNIT)
The memory unit of the computer collects the information
& instruction. These instructions are send to user by control unit
of arithmetical. Logical or output device the memory of computer is
measure in bit/ byte. Eight bit are equal ant 1 byte. Each word has
an address in memory. Generally CPU take a few seconds to reach the
address & find out that work. This time is known as access time.
The movement of computer will be very fast it access tome is short.

22. Page 22 of 31
COMPUTER LANGUAGE
There are three types of languages in computer---
1. Machine level language
2. Assembly language
3. High level language
MACHINE LEVEL LANGUAGE
Machine level language in completely based on two
dimension system. In this language different characters & key words
are very long. There for it is comparatively hard to understand or
remember & apply.
As result the speed of programming is reduced because of
there faults machine level language is known a low level language.
ADVANTAGES OF MACHINE LANGUAGE
1. Programs written in machine language can be executed
very fast by the computer.
2. This is mainly because machine instructions are
directly understood by the CPU & no translation of
the program is required.
3. It is very close to the machine & far from the
users.
DISADVANTAGES OF MACHINE LANGUAGE
1. Machine language are machine dependent. Being very much
machine oriented the language is difficult to learn
2. Although machine language is easily used by the computer it
is very difficult to write a program in this language,
3. It is very difficult to correct modify machine language
program.
4. In short, writing a program in machine language is so
difficult & time consuming that it is rarely used today.
ASSEMBLY LANGUAGE
In 1950 scientists failed lot & instructions an
assembly language to reduce the faults of machine language in this
language they use joint code in the place of numeric codes&
address this language was much faster l& easy in comparison to
machine language , e. g . They use add & sub in the place of
addition & subtraction .
ADVANTAGES OF ASSEMBLY LANGUAGE
1. They save time & reduce detail
2. Assembly programs are easier to modify than machine language
3. Assembly languages are easier to use than machine language.
4. Fewer errors are makes those that one made are easy to find.
DISADVANTAGES OF ASSEMBLY LANGUAGE

23. Page 23 of 31
1. Program is difficult & time consuming because assembly
language programs are not immediately executable.
2. Programming in an assembly language requires a high level
of programming skill.
3. An assembly language program contains more instructions as
compared to high level language program.
HIGH LEVEL LANGUAGE
High level language came into existence, after the
chronological of the assembly language. The main differences
between these two languages are that these languages are based on
problems instead of computer system. In these language we can do
the programming very fast & with this, there is no need about broad
knowledge of hardware to use these language. These days mostly high
level language are in use.
Example
BASIC (Johan kemony & Thomas Kurtz, 1964)
FORTRAN (Johan Baccus in 1957 at IBM company)
NOTE
There are two positions of electrical signals in this
chain---
1. Pulse
2. No pulse
Pulse is donated by 1& no pulse is denoted by 0 (zero).
These numbers (0,1) are known as bits.
These are three types of coding systems used in computer.
1. Binary code decimal system (BCD)
2. Extended binary code decimal interchange code system
(EBCDIC)
3. American standard code for information interchanges
systems (ASCII)
In BCD system 6 bits chain constitute 1 byte & EBCDIC &
ASCII system 8 bits chain constitute 1 byte.
There are provisions of parity bits in order to remove
the possibility of any mistake in the code of characters.
VDU
These are TV like screen connected to the computer which
is called VDU/monitor.
CPU
CPU of a computer it consists of circuits to perform
arithmetic & logic & also has circu9it to control & co-ordinate the
functioning of the memory & I/O units of a computers. (also known
as brain of computer).
HARD COPY

24. Page 24 of 31
When we get the output on the paper through the printer
is known as hard copy.
SHOFT COPY
When any matter or file copy one place to another place
is known as softcopy.
SOFTWARE
Software refers to the set of computer program procedures
& document etc.
Software means collections of program where objective it
is in hence the capability of hard ware machine.
eg.: Operating system, interpreter, compiler etc.
HARDWARE
The physical components of computer are known as
hardware.
Hardware refers to the physical device computer systems.
eg.: Keyboard, CPU, VDU, printer.
OR
Hardware are the physicals parts of the computer & it in
dudes all physicals parts cup input devices printer & secondary
devices output devices.
PROCESSING
Reading, writing, & manipulation of data known as
processing. It is the stage when the data is arrange in readable
information.
PROGRAM
The set of logically arranged instructions is known as
programmed.
PROGRAMMING
The technique methology by which program can be written
is known as programming .
ALGORITHM
The term algorithm is defined as a sequence of
instructions. Step by step procedure to solve any problem is known
as algorithm.
CHARACTERISTICS OF ALGORITHM
1. Each very instruction must be precise & correct.
2. Each instruction should be such that it can be performed in
a finite time.
3. One or more instruction should not be repeated infinitely.
This ensures that the algorithm will ultimately terminate.
4. After performing the instructions that is after the
algorithm terminates, the desired result must be obtained.

25. Page 25 of 31
eg. The algorithm for adding two numbers.
Step 1. Start the execution of program.
Step 2. Input the value of variable a.
Step 3. Input the value of variable b
Step 4. Add the value 01 variable a & b & assign
the result in variable c.
Step 5. Display the value of variable c.
Step 6. Stop the execution of programs.
FLOWCHARTING
Flowcharting is second method of problem solving. The
flowchart system introduced by john von numan in 1945. The symbol
used by making flow charts have been standardized by ANSI.
Flow Lines
I /O
Yes
Connectors
Diamond
/
Decision
No
Start / stop
Process
PROGRAMMING APPROACHES
(I) Top Down Design (Ii) Bottom Up Design (Iii)Linear
Programming (Iv) Structured Programming
TOP DOWN DESIGN
The top down approach is based on the fact that the large
problems become more ,manageable if they are divided into a large
number of smaller & simpler tags which can be tacked separately.
What really is required is that each of these parts had the
properties of the module.
BOTTOM UP DESIGN
A bottom up approach would be to write the most basic
subroutine in the hierarchy first & then use them to make more
sophisticated subroutines. The pure bottom up approach is not
recommended because it is difficult to anticipate which low level
subroutines will be need for any particular program.
LINEAR PROGRAMMING
Linear program is the straight forward programming
sequential manner. This type of programming does not involve any
type of decision making. General model of a linear program is

26. Page 26 of 31
(1) Read the data value (ii) compute an intermediate
result to compute the desired result. (iii) Print the answer.
(iv) Stop
STRUCTURED PROGRAMMING
Structured program are those which are divided into
functional modules & arranged in an hierarchical order instead
programs written in sequence. There are procedures that can use for
writing these complex programs that make them less error prone &
much easier to debug. Structured programming refers to the process
in which we break the overall job down into separate piece of
modules. The modules are in turn broken into smaller pieces which
can also be further subdivided. Modules must be chosen in such a
way that we can specify how they are interacting.
TYPES OF SOFTWARE
Computer need clear cut instruction to tell them what to
do how to do & when to do. A set of instruction to carry out these
functions is called a program. A group of such programs that are
put into a computer to operate & control its activities are called
software. Software can be classified into two major categories.
(i) System software (ii) application software
SYSTEM SOFTWARE
System software’s are the programs used to control the
operation of the computer system & aid the program in doing its
work efficiently. These programs provide the integration of various
components of computers to work together. It cab be many category.
Such as operating system software translator etc.
OPERATING SYSTEM
An operating system is a system software that controls
the internal activities of the computer hardware & provides user
interface. All application program need to be programmed in such a
way that they talk with the operating system for interacting & use
hardware resources. eg.: DOS, WINDOWS, UNIX, LINUX, SOLARIS & OS/2
All operating system can be classified into four general
categories.
SINGLE USER OPERATING SYSTEM
Operating system which allows only one user to work on a
computer at a time is known as single user operating system. Eg,
DOS, WINDOWS 9X etc.

27. Page 27 of 31
MULTI-USER OPERATING SYSTEM
A multi-user operating system allows a number of users
to work together on a single computer. Each user will be provided a
terminal connected to a single computer. eg. LINUX, UNIX, WINDOWS
NT etc.
SINGLE TASKING OPERATING SYSTEM
Operating system which can execute only a single task at
a time is known as single tasking operating system. Eg, DOS.
MULTITASKING OPERATING SYSTEM
Multitasking operating system supports execution of more
than one job at a time on a computer. Most of today’s operating
systems such as WINDOWS 2K, OS/2, UNIX, LINUX etc.
FUNCTION OF AN OPERATING SYSTEM
There are many functions of operating system.
(i)processor management (ii) memory management (iii)
i/o management (iv) file management (v) scheduling (vi)
timesharing (vii) security management
PROCESSOR MANAGEMENT
The operating system assigns processors to the different
tasks that be performed by the computer system.
MEMORY MANAGEMENT
It (OS) allocates the main memory & secondary memory to
the system programs user programs & data.
I/O MANAGEMENT
It carries out the I/O management & co-ordinates &
assigns different I/O devices.
FILE MANAGEMENT
It manage files or various storage devices & the transfer
of these files from one storage device to another it also these
files from one storage device to another
SCHEDULING
It establishes &enforces the job priority that is it
determines & maintains the order in which jobs are to be executed
in the computer system.
TIMESHARING
It co-ordinate & assign compilers, utility programs,&
other software packages to various users working on the computer
system.

28. Page 28 of 31
SECURITY MANAGEMENT
It establishes data security & integrity that is keeps
different programs & data in such a manner that they do not
interfere with each other moreover; it also protects data from
being destroyed by any other user.
TRANSLATORS
Translator is a program that takes as input a program
written in one programming language. Translator can be classified
into two major categories
(I) Compiler (II) Interpreter
COMPILER
To check the whole program at a time & then executer the
error free message.
INTERPRETER
To check the program line by line
APPLICATION SOFTWARE
It enable the computer to produce some output. These are
developed by specialist software programmers to solve common
problem faces by manby user. eg. Ms office.
BLOCK DIAGRAM OF THE COMPUTER
CPU
CU
ALU
INPUT OUTPUT
MU
1. CPU CENTRAL PROCESSING UNIT
2. VDU visual display unit
3. CU control unit
4. MU memory unit
5. ALU algorithm logic unit

29. Page 29 of 31
BOOTING
Booting means to load the operat9ing system into the
primary memory of the computer is known as booting.
They are classified into two categories
(I) Cold booting (II) Worm Booting
COLD BOOTING
When we on the main switch of computer & check the self
I/O devices after then load the operating system int6o the primary
memory of the computer.
WORM BOOTING
When we press the reset button of the front of the
cabinet or use the CTRL +ALT+DEL key for restarting the computer.
NECESSARY FILES FOR BOOTING
(I) COMMAND.COM
Previously internal load the operating system into the
primary memory of computer then execute the prompt(c:>) sign.
(II) MSDOS.SYS
To check the commands. Like as date, time, cls, ver, dir
etc.
(III) IO.SYS
To check the peripheral devices.
FILE ORGANIZATION
File organization can be classified into four major
categories.
(I) serial file (I) sequential file (III) direct / random
access file (IV) indexed sequential file
SERIAL FILE
In a serial file the records are placed one after the
other serially. The records are physically adjacent to one another
on the medium. However there is no specific order in arrangement of
these records. On a magnetic tape storage device, the records of a
serial file are written along the length of the tape while on the
disk they are written along the track, one after the other.
SEQUENTIAL FILE
A sequential file is one in which the records are kept in
some sequence. A student file may be kept in the order of roll
number. It is not necessary that records of a sequential file
should be physically in adjacent positions. However on magnetic
tape serial & sequential file organization, the records are written
one after the other along the length of the tape. In case of disks,
the records of a sequential file may not be in adjacent locations.

30. Page 30 of 31
DIRECT / RANDOM ACCESS FILE
Random access file organization is best suited for on
line processing systems where current information is always
require. It is not necessary for the user to know where the record
is kept on the disk.
INDEXED SEQUENTIAL FILE
An indexed sequential file is basically a sequential file
organization serially on a key field, in addition, an index is
maintained which speeds up the access of isolated records. Just as
you may use indexes to located information in a book, an index is
provided for the file. The file is divided into a number of blocks
& the highest key in each block is indexed.
SECURITY OF SYSTEM
Computer security is the ability of a system to protect
information and system resources with respect to confidentiality
and integrity.
BASIC COMPONENTS OF COMPUTER SECURITY
Computer security is frequently associated with three
core areas, which can be conveniently summarized by the acronym
“CIA”.
(I) CONFIDENTIALITY
Ensuring that information is not accessed by unauthorized
persons.
(II) INTEGRITY
Ensuring that information is not altered by unauthorized
persons in a way that is not detectable by authorized users.
(III)AUTHENTICATION
Ensuring that users are the erosn they claim to be.
Computer security is not restricted to these three broad concepts.
Additional ideas that are often considered part of the taxonomy of
computer security include:
(I) ACCESS CONTROL
Ensuring that users access only those resources and
services that they are entitled to access and that qualified users
are not denied access to services that they legitimately expect to
receive.
(II) NON REPUDIATION
Ensuring that the originators of messages cannot deny
that they infact sent the messages.

31. Page 31 of 31
(III) AVAILABILITY
Ensuring that a system is operational and functional at a
given moment, usually provided through redundancy; loss of
availability is often referred to as “denial-of-service”
(IV) PRIVACY
Ensuring that individuals maintain the right to control
what information is collected about them, how it is used, who has
used it, who maintains it, and what purpose it is used for.
Threats to computer security
A threat is a potential violation of security. When a
threat is actually executed, it becomes attack. Those who execute
such actions, or cause them to be executed are called attackers.
Some common threats the average computer user faces every day are
being given below
1. Viruses(eg: worms, Trojans)
2. Spyware
3. Adware
4. Spamming
5. Pc instruction(denial of service, sweeping, password guessing)
6. phishing