Computer

A computer is an electronic device that can accept, store and process

information to produce the required result.
The word “computer” comes from the word “compute” which means to
calculate. We can store bulky data in it. The computer has memory that can
save a lot of information and can take logical decisions like human beings.

Uses of Computers
Computers have a significant impact on modern society. Now days
nearly every profession uses computers.

Computers are used in

· Airline and Railway Reservations.
· Medical Diagnosis
· Weather Forecasting
· Payment of telephone and electricity bills
· Banking
· Manufacturing products like automobiles, shoes, computer cabinets
etc.
· Cartoon film production
· Space research
· Creation of blueprints for houses.

Computer System Characteristics

Speed: Computers are very fast computers can perform innumerable opera-
tions in just 1 second. The processing speed of a computer is generally mea-
sured in nanoseconds. The speed of computer is measured in terms of Million
Instructions per seconds. (MIPS)

Storage: A computer can store large amounts of information in its memory.

Computers have very large storage capacity. Every piece of information can
be retained as long as desired by the user and can be recalled as and when
required. Even after several years. The information recalled would be as on
the day when it was fed to the computer.

Accuracy: The accuracy of a computer is consistently high and the degree of

accuracy of a particular computer depends upon its design. A computer per-
forms each and every calculation with the same accuracy.

Diligence: Computer is free from monotony, tiredness and lack of concentra-

tion. It can do work for hours without creating any error. If five million calcula-
tions have to be performed a computer can perform the 5 million calculation
with the same accuracy and speed as it performed the first calculations.
Versatility:Computers can perform a wide range of jobs with speed, accu-
racy and diligence. Computers are used for diverse purposes such as ac-
counting, generating, pay-slips, keeping track of manager’s appointments,
play games during the recreation hours.

Inputting:The process of entering data and instructions into the computer

system is known as inputting. We can enter data and can give instructions to
perform a particular task.

Storing: Data’s and information can be stored in a computer system. The stored data
and information are available for initial or for additional processing as and when re-
quired.

Processing: The computer system can perform arithmetic operations or logical op-
eration (like comparisons like equal to, less than, greater than etc.) on data in order to
convert them into useful information.

Outputting: A computer gives result of a work. The process of producing

useful information or result for the user is known as output. Output can be
getting on monitor that can be only visually seen or in printed form through a
printer.

Controlling : In computer system controlling means directing the manner and

sequence in which all of the above operations are performed.

Limitation of Computer: The computer provides too many facilities and ben-
efits to the user. But it has some limitations. Those are as following:

Hasn’t I.Q.: The computer hasn’t I.Q. It has to be told what to do and in what
sequence. Only user can determine what tasks a computer will perform.

No Feelings: The computer has no feelings and no instincts because it is a

machine. Computer cannot make judgments of their own. Its judgment is
based on the instructions given to them in the form of programs that are writ-
ten by us.

Can’t remove error itself:The computer can’t remove errors itself. If an

unanticipated situation arises, computers will produce wrong results or aban-
don the task. They do not have potential to work out alternate solutions.

Can’t work without human being: Computer can’t perform any task on its
own. It can’t take independent decision. It requires human instruction to take
a decision or what to do.
HISTORY OF DEVELOPMENT OF COMPUTERS
Computers are invented as a result of man’s search for fast and accu-
rate calculating device. Computer is developed passing through different
stages. They are as following:

Abacus : Abacus is considered to be the first computer and was invented by

the Chinese about 5000 years ago. The basic purpose of the device is to
make calculations. It consists a rectangular frame with a number of strings.
Each string has a collection of beads. These beads are used to perform cal-
culations.

Charles Babbage’s Mechanical Computer : Charles Babbage invented the first

mechanical computer during the period of 1830 to 1850. This computer performed
basic arithmetic functions. Babbage is known as the father of modern digital comput-
ers.

Punched Cards:The next device that contributed to the evolution of comput-

ers was the punched cards. These cards were made up of special pulp refer.
Machines were used to make holes in the card and to store information.

The Mark-I Computer :

This was the first fully automatic calculating machine. It was designed
by Howard A. Aikne it collaboration with IBM.
This machine was proved to be extremely reliable. It was very complex
in design and huge in size.
It was capable of performing five basic arithmetic operations, addition,
subtractions, multiplication, and division and table reference.
The Atonasoff - Berry Computer (1939-42)
This electronic machine was developed by Atanasoff to solve certain
mathematical equations. It used 45 vaccum tubes for internal logical and ca-
pacitors for storage.

Electronic Numerical Integrator and Calculator (ENIAC)

It was the first electronic computer. It was built by a team of professors
at more school of university of Pennsylvania. It was a bulky machine consist-
ing of 18000 vaccum tubes. It was based on decimal arithmetic.

Electronic Discrete Variable automatic Computer (EDVAC)

It was designed on stored program concept. Dr. John Von Neumann in-
troduced it. The basic idea of stored program is that a sequence of instruc-
tions as well as data can be stored in the memory of computer. Neumann got
a share of credit for introducing the ideas of storing both instructions and data
in the binary form (0&1) (in 1950 Cambridge).

First Generations :
 The computers produced between 1942-1955 are called the first gener-
ation computers. They were extremely large with low reliability. These ma-
chines were made possible by the invention of “Vaccum Tube”. IBM 650 was
the most popular first generation computer. It was used for both business and
scientific applications.

Advantages of first generation computer

· Vaccum Tubes were the only electronic components available during
those days.
· Vaccum Tube technology made possible the advent of electronic
digital computers.

Disadvantages of first generation computer

· Too bulky in size.
· Unreliable
· Thousand of vaccum tubes that were used emitted large amount of
heat and burnt out frequently.
· Air conditioning required.
· Prone to frequent hardware failures.
· Constant maintenance required.
· Not portable

Second Generation:
In second-generation computers advanced technology can be used.
Vaccum tubes were replaced by Transistors. These components were
smaller in size, easier to manufacture, less power consuming, cheaper &
more durable. Computer storage technique improved with the use of mag-
netic disks. The machine language was replaced by high-level language like
FORTRAN IBM 700 was one of the computers.

Advantages of Second Generation Computer:

· Smaller in size as compared to first generation computers.
· More reliable
· Less heat generated

These computers were able to reduce computational times from milliseconds

to microseconds.

Disadvantages of Second Generation Computer

· Air conditioning required.
· Frequent maintenance required.
· Manual assembly of individual components into a functioning unit
was required.
· Commercial production was difficult and costly.
Third Generation
The third generation computers employed integrated circuits. The inte-
grated circuits (IC) based on the small, medium and large Scale integration
(LCI) Technology replaced Transistors. The LCI technology led to the devel-
opment of very small but extremely powerful micro- computers.

Advantages of third generations computers:

· Smaller in size as compared to previous generation computers.
· Even more reliable than second-generation computers.
· Even lower heat generated than second generation computers.
· Maintenance cost is low because hardware failures are rare.
· Easily portable.

Disadvantages:
· Air conditioning required in many cases.
· Highly sophisticated technology required for the manufacture of IC
chips.

Fourth Generation
The fourth generation computers used VLSI (very large scale integra-
tion) technology. The VLSI devices have thousands of more components
packed into an assembly. This technology led to the development of micro-
processors, where on entire CPU circuitry is placed on a single chip. Comput-
ers like IBM PCs, Apple Macintosh, sun Spare stations etc. fall under this
generation of computers.

Advantages of fourth generation computer:

· Low cost machine.
· High speed
· Large memory
· Small size
· Less power consumption
· Hardware failure is negligible
· Heat generated is negligible
· Cheapest among all generations.
Disadvantages
Highly sophisticated technology required for the manufacture of ISI
chip.

Fifth Generation
Scientists are now at work on the fifth generation computers. They aim
to bring us machines with genuine I.Q. This Generation is under develop-
ment. Size of computers became small like laptop. Notebook etc. Develop-
ment of Internet, multimedia and develop software according to task like ac-
cording to business, hospital and traffic control etc.
TYPES OF COMPUTERS :CLASSIFICATION OF COMPUTERS

Today several types of computers are available in the market. Through each
computer we can do different type of work like: Calculation work, weather
forecasting. Statistical analysis for business management etc. All types of
computers are available in different sizes. They have different capabilities.

1. Classification based on application/computational method.

2. Classification based on purpose.
3. Classification based on size and capability.

1. Classification based on application:

In applications computer is designed for different type of work according to re-
quirement. Computer is divided in three parts on the basis of application.

(i) Analog Computer

(ii) Digital Computer
(iii) Hybrid Computer

(i) Analog Computer:

Analog computer is a special purpose computer. Through their we can
take result in the form of measurement because this type of system is worked
on quantity like in petrol pump, weather forecasting, temperature etc. Analog
computers process data input in a continuous form.

Advantages :
· Analog computers carried out measurement by a few single purpose
devices. So the analog computer offers low cost.

Disadvantages:
· The main disadvantage of an analog computer is the accuracy fac-
tor. The result of analog computers are not accurate.
· Analog computer has limited storage capacity.
· Analog computers are not suitable for processing business data.
(ii) Digital Computers:
It is a general computer. It is used for all general purposes. It gives accu-
rate result because this computer uses digital signals for working. A digital
computer can count, and accept numbers and letters through various input
devices.
1. Strong data for processing.
2. Performing logical operations.
3. Editing or deleting the input data.

Advantages:
· Digital computers gave any desired level of accuracy. It can be
achieved by considering as many places of decimal as are neces-
sary.
· Digital computers are most suitable for business application.

Disadvantages:
· The main disadvantage is high cost of digital computer.
· Digital computers have complexity in programming.

(iii) Hybrid Computers

This computer is a combination of analog and digital computer. For this
computer both analog and digital signals worked. It can convert’s the analog
signal to digital signal and digital signal to Analog signal. This type of system
is mostly used in hospitals. Modem is an example of hybrid system.

2. Classification based on purpose.

Computers are also designed according to work. There are two types of com-
puter in this category.

(i) General purpose computer

(ii) Special purpose computer

(i) General purpose computer:

General-purpose computer is a normal computer. Which is used every-
where. This type of computer can do programming, calculation, accounting
work, painting work etc. This computer is mostly used in homes, schools and
colleges etc. Digital computer is an example of general-purpose computer. It
is available in different sizes.

(ii) Special purpose computer:

This computer is designed according to different tasks like for weather
forecasting to make a film in photo studio etc. These computers are used
rarely. In the category of special purpose computer digital. Hybrid and analog
computer exist.
3. Classification based on size and capability:
In this category computer is divided into four parts

(i) Micro computer

(ii) Mini computer
(iii) Mainframe Computer
(iv) Super Computer

1. Micro Computer
It is very smallest computer. This type of computer consist a micropro-
cessor and associated storage and input/output devices. It is portable we can
move it easily from one place to another. Its storing capacity is very slow. Its
speed is also slow.
Example like Palmtop, Notebook etc.

Digital Diary
Microcomputers were first available for widespread use in the 1970’s
when it becomes possible to put CPU into a small silicon chip.

2. Mini Computer
Minicomputer is bigger than microcomputer. It is known as general-pur-
pose computer. This computer is used in schools, colleges and homes etc.
These computers can perform more complex tasks and cost more than micro-
computers. They are used for processing data and analyzing results of exper-
iments. They are also used for controlling ad monitoring production pro-
cesses. Its data transfer rate is high. We can connect many computers app.
50 computers. Some examples are PDP 11/42, Vax 11, and IBM series.

Desktop and laptop computers etc.

Mainframe Computer
Mainframe computers are more powerful and costly than minicomputer.
They are special computers, big in size. They are capable to handle all kinds
of scientific and business applications. They can process several million in-
structions per second. Its storing capacity is very high and data transfer rate
is too high. It has large on-line secondary storage capacity. We can connect
more than 500 computers through this. They are used in Wan. These com-
puters consume more electricity.
Mainframe computer such as ES/9000 family of IBM Corp. are used for
such applications as payroll computations, accounting, business transaction
information retrieval and airline seat reservations.

They are used in big companies and factories like BHEL, BSNL, and
NTPC etc.
(iv) Super Computer
Super computer is the largest and fastest computer. They are also
costliest computer. They are not used for commercial data processing. They
are used in fields like Science and Defence.Supercomputer can process 64
bits or more at a time. Its processing speed ranges from 10,000 million in-
structions per second (MIPS) to 1.2 billion instructions P/sec.
They can support 10,000 terminals at a time. They have huge numbers
of storage and other devices connected to them.
Example of Supercomputer is CRAY-1, CRAY-2, and CRAY-3.
Today India is making Super Computer PARAM-10000.

Personal Computer (IBM PC)

First personal computer is designed by IBM (International Business Machine)
company. In this computer 8056 microprocessor was fixed. In this computer
data storing is in kilobyte. In this computer one or two floppies were used.
There was no hard disk in the computer. 8 bit data is use in personal com-
puter. We can do mathematical calculation in this computer.

Types of PC (Personal Computer)

1. Desktop
Desktop is a microcomputer. It can be shift from one place to another place. It
can be put over table. It is used in home, schools, college etc. Its storage ca-
pacity is very high. Through this computer we can joint more than one com-
puter system. Its storage capacity is in the form of GB. We can use floppy
disk & CD.

2. Laptop
Laptop is a briefcase type computer. It works with electricity as well as with
battery. Its working is similar to desktop computer. It is costlier than desktop.
Its storage capacity is in Giga bytes (GB). Floppy and CD is used in laptop.

3. Notebook
Notebook’s size is very small. It can be keep inside of pocket but in this com-
puter we can’t work like a desktop and Laptop computers. There is no typing
pad is available in this computer. Light pen is used in this computer to write
information. Light pen is directly worked on screen.
Examples contura 3/20 and Acer Anware etc.

4. Palmtop
Palmtop is a small computer. It has the size of a pocket calculator. It is not as
powerful as desktop. They support only a few applications.
It can be keep inside of pocket its storage capacity is in MB (mega byte).
Through this calculation can be done and can store information also. It is
mostly used in stock exchange.
Example HP 95 LX.
Workstations
In workstation computers desktop computer is use. In this more than one
desktop computer can be connected with each other. Monitors are very big
like 19”. monitor configuration of workstation system is very high, like proces-
sor speed, memory storage, size of RAM etc. (Similar to server) speed of
connected computer depend upon workstation .

Basic computer organization

1. Central processing unit: (CPU)
A central processing unit (CPU) controls the execution of programs and per-
forms the calculations. The CPU is also called as the brain of the computer.
This is because executions of any task by a computer are controlled entirely
by the CPU.

A CPU performs following tasks: -

· Manipulating alphabetic or alphanumeric data like word processing,
letter
· Writing, sorting in alphabetic or alphanumeric orders, editing, making
catalog etc.
· Storing the data temporarily and retrieving it as and when required.
· CPU does everything in binary language (0&1)

Arithmetical and Logical Unit (ALU)

Computer’s has to do a large number of calculations and computations. ALU
is designed to perform the four basic arithmetic operations, like add, subtract,
multiply, divide and logical operations of and or comparisons such as less
than, equal to or greater than. It can do complex calculations with fast speed.

Control unit
This unit controls the internal functioning of the computer and input or output
units the control unit directs call operations inside the computer. It is known
as nerve center of the computer. It manages and co- ordinates the entire
computer system.

Input Unit
Input unit is a device which provides man to machine communication with
computer. Input of any form is first converted into binary electronic signals
(0 &1), which can be understood by CPU. This process is called digitizing.

Inputs data may be linguistic, mechanical, graphical, and audiovisual.

· Linguistic input is given to computer by keyboard or punch cards,

floppy disk, magnetic tape and cassettes.
 · Audio input is given to computer through voice data entry (VDE),
which has got a microphone
Work of input unit
· The input units converts our everyday languages into binary patterns
for the machine and transfer it to the memory.
· The memory stores the input information (the program and data). It
also stores the data processed in the arithmetic unit.
· Data and instructions from the memory are transferred to control unit
and from arithmetic unit by the control unit.
· The arithmetic unit processes the data and sends it back to the
memory.
· From the memory, the processed data is converted from binary pat-
terns to humanly understandable language.

OUTPUT UNIT
Output unit of computer gives result. The output coming from the CPU is in
the form of electronic binary signals which needs conversion to make it un-
derstandable by human beings, i.e. graphical, alphanumeric in human lan-
guage, audio – visual. Output units perform this function. The output can
be given:

1. On the screen by visual display unit.

2. In printed form by printers
3. In graphic form by plotters.
4. In audible sound form by speech synthesizers.
5. Through other output devices.

Computer System Memory

Memory is a location to store something. Computer memory is used to store
data, information and programs. A computer works like the human brain,
computer can’t do work without it.

Computer uses two types of storage or memory.

Memory
Internal / Primary External / Secondary
Ram Rom Floppy Disk
Dram Sram Prom EPROM EEPROM HARD DISK

CD ROM
TYPES OF MEMORY USED IN COMPUTERS

Primary or Internal memory

Internal memory is known as main memory or primary memory. The primary
memory of a computer stores the data provided by the user and the instruc-
tion provided by the programs. It is a portion of CPU where current data or
program resides for execution in computer.

It stores the results also which can be there after transferred to output unit.
The primary memory is placed on the motherboard in the form of chips.

Main memory stores:

· Instructions waiting to be obeyed by other components of the CPU.
· Instructions currently being obeyed.
· Data waiting processing.
· Data currently being processed.
· Processed data awaiting output.

Use of Primary memory

1. Data are fed into an input storage area where they are held until ready
to be processed.
2. A working storage space is used to hold the data being processed and
the intermediate result of such processing.
3. An output storage area holds the finished results of the processing op-
erations until they can release.
4. The primary storage section contains a program storage area that holds
the processing instructions.

Classification of Primary Memory

Primary memory classified into following group
1. RAM (Random Access Memory)
2. ROM (Read only memory)

1. RAM
Whenever a computer receives any information, it stores it in the RAM. Input
data is stored in this memory before it goes to the processor for actual pro-
cessing. The storage capacity of RAM may vary in different computers. The
characteristics of RAM are: -
· We can read data from RAM as well as write data onto RAM. Ram is
also called Read and w0rite memory.
· Ram is volatile, because information stored in RAM is lost when the
computer is switched off.
RAM can be of two types
1. DRAM (Dynamic RAM)
2. SRAM (Static RAM)

1. DRAM – (Dynamic RAM)

In DRAM the memory element have less retention period and loses its value
unless it is refreshed. Refreshing is a process where the RAM is read and
rewritten. This kind of RAM requires extra circuits for refreshing. These are
relatively slow but less costly compared to static RAM. This kind of memory is
therefore used in mass scale.

2. STATIC RAM:
SRAM chips are also volatile storage devices. Static RAM elements once set
to their values, don’t loose them if the power supply doesn’t go off. If some
value is stored, it will remain in the main memory till the power is on. SRAM
chips are more complicated and take up more spaces for a given storage ca-
pacity.

Rom (Read Only Memory)

There are portions in the computer memory where no writing is allowed. The
contents are pre written and can only be read. Such memories are called
Read only Memory (ROM). It is used for micro-programs not available to nor-
mal programmes.
The term read only means that the storage can’t be attired by regular
program instructions. The information from the memory may be read out but
rush information can’t be written into it (BIOS)

TYPES OF ROM
1. PROM -PROM are those in which the user can insert the contents of
choice only once. It can only be read and never written means recorded infor-
mation can’t be changed. PROM is non-volatile storage.

2. EPROM-In EPROM information can be erased and the chip can be pro-
grammed to record different information. Eraser is achieved by exposing the
chip to ultraviolet light. EPROM is also known as UPROM (ultraviolet PROM)
or EAPROM (electricity Alterable)

3. EAROM -It is a recently developed type of memory can be programmed

and erased by electrical signals. This type is called electrically alterable read
only memory.
4. EEPROM -It is a memory, which can be easily re programmed by the appli-
cation of a small voltage.
UNIT II

Input Devices
Those devices’s, which are used to giving instructions or data in CPU, are
known as input devices. Data and instructions must be entered into the mem-
ory of the computer to perform computation. The input devices carry out this
task.
All input devices provide data to memory in binary form (codes of 0.41) work-
ing principles of each device is different. All devices will have an interface,
which will enable the device to communicate with the system.

Functions of Input devices

1. It accepts (read or input) the data form outside world.
2. It converts the data into the ASCII code or binary form.
3. It sends data in binary form to the computer for further processing.

Names Of Input Devices

1. Keyboard
2. Mouse
3. Light Pen
4. OCR (Optical Character Reader)
5. OMR (Optical Mark Reader)
6. Bar Code Reader
7. Joy stick
8. Voice Recognition
9. Digital camera
10. Web Camera

1. Keyboard -It is a general-purpose device as like a typewriter machine. We

can type alphabets, numerical and special characters through it. A computer
contains only binary number in the form of 0 &1. It has some function keys
also. It is connected with CPU.

2. Mouse -This device is worked on GUI (Graphical user interface) based ap-
plications GUI based application contains written commands. We use a
mouse click to execute these commands. It is connected with CPU. Mouse
has two button left and right.

3. Light Pen - Light pen is a free hand writing pen. We can draw any sketch
and can do signatures. This device is connected with CPU. This pen contains
the laser beams to draw anything. It is used over the screen (monitor) and
light pen pad.
One can sign an authority letter from far place by light pen.
4. OCR (Optical Character Reader)
It is a special device. It reads only special character, which is known as
optical character. These optical characters are in combination of black and
white. Computer reads 1 for the black and 0 for the white character.

There are two types of scanners:-

1. Hand remote scanner
2. Flat bed scanner

Hand remote scanner is used for small images. Composing for visiting cards,
marriage card and monos.

5. OMR (Optical mark reader)

It is also a special device. It is used in the examinations like in railway,
bank or PET Exam. This device reads special characters, which are ap-
peared on computerized sheet. The software handles this device.

6. MICR (Magnetic Ink Character Reader)

This device is used only in banks. It read MICR number, which are ap-
peared or mentioned at the bottom of cheque or drafts. These numbers are
used to stop delicacy.
There are two types of MICR number fonts: -
-E-13 B font style
-CMC- 7 Font style

7. BAR CODE READER

It is a special device, which reads the bars and appeared on various
items. This device stops the delicacy of the products. Each bar contains the
manufacturing number and item.

8. Joystick:
This device is similar to mouse. But is not used nowadays. This device
contains a stick, which can easy to move. The mouse pointer is moved on the
screen according to movement of stick. But today mouse is used in place of
that.

9. VOICE RECOGNITION
It is also an input device. It detects voice.

11. WEB CAMERA

 This camera is mostly used in Internet. This device reads the moveable
movies but it doesn’t work without computer.

OUTPUT DEVICES:
Those devices, which are used to give a softcopy or hardcopy result is
known as output devices. This output can be displayed on monitor or printed
on paper by using a printer.

Names of output devices: -

1. Monitor
2. Printer
3. Plotters
4. Speaker

Hardcopy result can be derived from printer. Softcopy result can be seen on
monitor.

1. Monitor or visual display unit: -

A screen like T.V. connected to the computer is called the video display
unit (VDU). It displays graphics, characters and number on screen.

Monitor has following characteristics: -

1. The computer has a screen to display output.
2. The computer screen is called VDU or monitor.
3. The monitor of the computer resembles a television screen.
4. It can display colored as well as black and white output.
5. A computer can display data in two modes, text and graphics. In text
mode, individual characters are displayed. In graphics mode, images
are displayed.
6. Images are formed on the monitor’s screen by a card called the display
adaptor card. The PC can’t display output without this card.
7. This unit provides soft copy result.
8. We can see its output visually.

Types of Monitor

There are two types of monitors is used to see the results

1. Colour monitor
2. Monochrome monitor

1. Colour Monitor
There are three basic colors used in this monitor. Red, Green, Blue
(RGB). Today color monitors are only available.

2. Monochrome monitor
 Monochrome monitor used only two basic colors black and white. Moni-
tors create information in the form of dots.

Two types of picture tubes are used in a monitor.

1. CRT (Cathode Ray Tube)
2. LCD (Liquid Crystal display)

1. CRT (Cathode Ray Tube)

A cathode ray tube screen is generally found in desktop workstations. It
is larger transportable PC models. It is broad. It can’t move easily and
cheaper. It is not used in small portable computer.

2. LCD
LCD is costly. It occupies less space. It can move easily. Its picture
quality is better.

RESOLUTION
This inside of the screen is coated with dot of phosphorus called pixel. It
can be used for games or graphics or displaying the result of a calculation
done by computer. The more is the number of pixel or dots in a screen, the
better will be the capacity of computer to display on information. This capabil-
ity is known as resolution.

DOT PITCH
Dot pitch is not a hardware component. It is a method that is used in a
monitor. Through this option can check the quality of resolution. If two pixels
gape is more increased, monitors resolution isn’t good. The gape of two pix-
els can be measure with the help of dot pitch. Pixels are set by machine.

REFRESH RATE
Refresh rate is a method. This option is used for monitor. We can see
the changes of screen with the help of this option.

Right click on desktop - Setting – can set pixel and colour.

## Video Cards
1. VGA (Visual graphic adaptor)
2. SVGA (Super visual graphic adaptor)
3. XGA (extended graphic adaptor)

Through this card pixel, monitor colors and resolution can be set. Each card
provides option of different color and pixels.

Best video card is SVGA. It can provide thousands of colors. It provides more
pixels. We can set colors and pixels in windows.
Right click on desktop – setting – can set pixel and colour.

PRINTER
It is an output device used to produce the hard copy of information on
paper. It is used to print the results of an operation performed by the com-
puter. Printers are popular output devices. The output information is in the
permanent readable form.

Types of printer
1. Character Printer: This printer prints only one character at a time. In
this printer character size is fixed previously. Example: - Dot matrix
printer.
2. Line printer: This printers print an upper part of complete line. It prints
one line of text at a time. In this printer alphabets size are not fixed.
That’s why its prints text as well as graphical information. Example: -
Chain or drum printer
3. Page printer: This printer can print both types information text as well
as graphical information. It can print one page at a time. Its speed is
very fast Example: - Laser printer.

Printer is divided into two categories

1. Impact printer
2. Non impact printer

1. Impact printer
Those printers, in which hammer technology is used for printing, are
known as impact printer. In impact printer the typeface means head or needle
strike on an inked ribbon and makes a mark on the paper. The most com-
monly used impact printer is the dot matrix printer.

Type of impact printer:

1. Dot matrix printer
2. Drum printer 300 to 2000 lines per minute
3. Chain printer 400 to 2500 character per minute
4. Daisy wheel printer 10 to 50 cps.

Dot Matrix printer

Dot matrix print characters, which are formed by using dots. It speed
range is 30 CPS to 600 CPS (character per second). It can print both text and
graphics. These types of printer can print in any language without any addi-
tional hardware.
DMP has following features:
The printer head of DMP has a vertical array of pins. As the head
moves across the paper, pins strike on inked ribbon to form a pattern of dots
on the papers. Using 5 dot rows and 7-dot columns form the capital letters. It
is called 5x7 matrix.

Non impact printer

Those printers in which hammer technique isn’t used called non-impact
printer. In non- impact printers, there is no contact between the typeface
(head or needle) and the paper while printing. It does not have any mecha-
nism to strike. It uses the chemical, thermal electrostatic, and laser beam or
inkjet technology for printing. These types of printers are faster than the im-
pact printers.

Names of non impact printers

1. Laser printer 2. Thermal 3. Ink jet printer

Laser Printer-
A laser printer uses a beam of light to form images on the paper. Laser
printers are used for printing both text and graphics. This printer uses a laser-
produced light to charge a photo conductive in the latest image of the charac-
ters to be printed. These printers are capable of very high speed. It can print
15,000 lines per minutes.

2. Thermal This is a type of the impact dot-matrix printer. In this printer nee-
dles are pressed against heat sensitive paper to form characters. There is
very little noise with thermal printing. The advantage of this printer is that the
terminals unit is much quieter. The disadvantage is that special type of paper
is must for this. It is not possible to produce multiple copies through it.

3. Inkjet Printer An inkjet printer produced characters by spraying small ink

droplets onto paper. A high frequency electrical generators used to vibrate
and throw off tiny ink droplets, supplied from a reservoir. This type of printer
has high speed. It prints 45,000 lines per minute with software control of
styles and size of characters. It is a costly machines, it is used for large vol-
umes of printed output. It provides color printing in its some models.

3. Plotter:
This device is similar to a printer. Plotter is used for graphical output like
pie charts, bar charts ands graphs etc. Engineers and architect use this de-
vice. It is used for designing. Plotters produce good quality drawings and
graphs have been designed. This can easily move in any direction. It is a spe-
cial purpose device. There are two types of plotters.
· Drum plotter
· Flat bed plotter

4. Speaker
 This output device provides soft copy result in the form of sound. Sound
card is compulsory to install in a computer to get result in speaker. Sound
card is must to insert the pins of speaker. It consists in CPU. It is fixed in
motherboard Nowadays sound cards are inbuilt in the computer.
Secondary Memory
This memory is designed for user. We can store information in permanent
form through this. This memory is divided into two important categories.

1. Sequential or serial memory-In this memory we can store read informa-

tion’s in a sequential method. It is a time consuming memory. That’s why
nowadays this memory is not in use audio - cassette.

2. Direct memory -In this memory we can store information and remove also
so that why today all memory devices using this concept .

Types of secondary memory

1. Hard disk
2. Floppy disk
3. Compact disk (CD)
4. Winchester disk
5. Magnetic tape
6. Cartridge tape

1. Hard Disk -Hard disk is an expensive storage device. Because this device
contains disc as well as drive. Its storing capacity is highest. This device
worked on a direct storage method. This device is fixed inside of CPU. Two
types of heads are used in hard disk.

A. Movable head -In this category there is only one head. It is moved at the
surface of the disk.

B. Non moveable head

This type of head contains too many heads according to tracks of disk. Head
doesn’t move at the surface of disk.
Storing capacity
1 character takes = 1 byte space
8 byte= 1 bit
1 KB = 1024 byte
1 MB = 1024 kilobyte
1 GB= 1024 megabyte
Computer stores in only bit (0,1)

2. Floppy Disk: It is a direct storage device. A small flexible disk used as

storage medium for small computer is known as floppy disk. It is used to store
information. Its storing capacity is very low. Its storing capacity is 1.44 MB.
This device is coated with magnetic particles. It is one of the most common
storage media that is usually used to move data from one location to another.
Today several sizes of floppies are available
(1) 3.5” inch floppy (2) 5.25 inch floppy (3) 8 inch floppy
3. Compact Disk-It is also a direct storage device. This device stores more
than floppy but less than hard disk. It is much reliable comparatively, floppy
disk. Its storing capacity is 650 MB to 750 MB. This disk is coated with mag-
net particles. In a CD only one side can be used for reading or writing pur-
pose.

CD is divided into two parts.

1. CD – R (Compact disk receivable)
2. CD-RW (Compact disk readable write able)

1. CD-R: In this CD only one time information can be write but we can read
information as and when we required. It is very cheap. Its cost is approximate
Rs.10 to 50.

2. CD-RW: In this disk we can read & write information’s so many times. This
disk is very costly. Its cost is app. 250 to 300. Storing capacity of both types is
same about 650 MB to 750 MB.

4. Magnetic Tape: It is an old storage device. It is worked on sequential ba-

sis. This device is not currently used because it is a time consuming device. It
stores information in the form of MB. The advantage of this device is that it is
most reliable storage device. Magnetic tape is used where information have
to keep for many years.

5. Winchester Disk: This disk is similar to hard disk. But this disk works fast
in comparison of hard disk. It is cheaper than hard disk. If some problem ex-
ists in disk, it can’t be repair because it is packed with a lubricant. It is used in
big computes like mainframe. Its storing capacity is in MB. It is air-free be-
cause it is sealed.

6. Cartridge Tape: Cartridge tape is a storage medium that is used to store

large amounts of data. It has two wheels.This tape is covered with a plastic
cover. It is used in large machines. Retrieving data from a cartridge tape
takes time. This tape is used to make a back up. It is mostly used in banks.
This device takes backup from only hard disk.

7. Zip Drive: Zip drive is a storage device similar to floppy. But its size is
greater than floppy. Its body cover is harder than floppy. Its storing capacity is
app. 100 Mb. Zip drive can be fixed in CPU and zip floppy can be insert only
in it. Zip drives are gaining popularity in the market. Zip disks are used for
lacking up hard disks and transferring large files. It is used to create zip disks.
Floppy:
It may cause physical damage and hence loss of data.
Always keep the floppies inside a paper cover. Don’t expose it to dust or heat.
Data Storage and Retrieval Method
1. Sequential method
2. Direct method
3. Index Sequential method

1. Sequential Method:
In sequential method information can be stored and retrieve in sequen-
tial concept. This method is implemented only in a sequential method device
like magnetic tape. It is a time consuming method. That’s why today this
method is not used.

2. Direct Method:
This method is known as Random method. Because any information
can be stored or retrieve directly in this method. This method is worked only
with optical disk like floppy, CD, hard-disk etc. It is mostly used method in
computer field because it is a time saving method.

3. Index Sequential Method:

This method is similar to direct method. It is used in a direct storage de-
vice like hardisk, floppy, CD etc. But in this method information can be re-
trieve through indexing because indexing is much faster.

COMPUTER VIRUS
About virus : Virus is a destructive program. It is destroyed the information
of a system. This program is automatically executed in a computer and it in-
creases automatically. If virus is inserted in a computer. Working of system
will be automatically changed. Virus is similar to diseases, which infect the
body the human being.
Two Pakistani brothers develop first virus in 1988. “Virus” name is
“Brain virus”. This virus infected the boot sector of a storage device. Virus can
insert through CD, floppy or hard disk.

Problems That Can Be Created In Computer, By Virus

1. Computer’s speed becomes slow
2. Files and folders names are automatically changed.
3. Files and folder’s icons are changed.
4. File size is changed. File size is increases.
5. File extension is automatically changed.
6. File information destroys slowly.
7. The process of shut down became automatically slow. It takes two
much time to shut down.
8. System booting process became slow.

Different Types of Virus Creates Different Problems

1. Boot sector virus
2. File virus
3. Table partition virus.

1. Boot Sector Virus: This virus is attacked on bootable sector of a storage

device. Bootable virus affected when the computer is booted. This virus first
loaded in a memory then booting process is started. This virus infected the
system files of bootable sector like MSDOS.Sys, Command.com. etc.

2. File virus:This virus is directly attacked on stored files of a system. When-

ever a file is opened, virus attacked on it automatically. It corrupts the infor-
mation of a file. So that file can’t do work properly. It destroys the contents of
files which are opened by censes. This virus is loaded automatically when the
booting process of computer is completed.

3. Table Partition Virus: This virus is used to destroy the partition table of
any storage device. If a partition of a table is destroyed. System can’t access
particular part of hard disk. The other drives of disk exists but can’t reach at
other drive. We can’t see other drives and can’t get files or stored information
of that drive.

Types of Virus:
1. Brain Virus 2. Pentagon 3. Friday -13 4. 1 April 5. Saturday 6. Isralti Virus
7. Dog virus 8. Night Virus 9. Rabbit virus

Antivirus : Antivirus is also a program. Through this we can trap the system
virus and then remove it, Anti virus is similar to medicine. Today several types
of Anti viruses are available like Norton Anti Virus, PC-Cilline, boot-p etc. It is
necessary to update anti virus. Today through Internet we can easily update
anti virus. Anti virus is also available piratedly. Norton is most popular anti
virus. It detects any type of virus.

Methods To Prevent from Virus

1. Floppy must be scan by anti virus before use.
2. Before to copy or download any file from Internet, It should be scan by
anti virus.
3. Right protected notch should be used in floppy.
4. Games should not be played in computer

Basic sources of virus are

1. Storage device (CD, floppy, hard disk)
2. Through Internet

SOFTWARE
Software is a collection or set of commands or set of instruction, which can be
seen only but can’t touch, is known as software. Software is basically de-
signed to solve any task. Computer system is whole operated and handled
software’s like Word, Excel, Paintbrush, Dos, Window’s etc.

Software is divided into three categories.

1. System Software or operating software
2. Application software
3. Utility software

1. System software: That software’s which are used to operate whole com-
puter system is known as system software. System software is a collection of
programs, which are designed to operate control and extend the processing
capability of the computer system. System software comes along with com-
puter system. These programs are used for starting the computer, controlling
and managing its resources, converting high level language program to ma-
chine language or for some specific purposes.
Today several types of system software’s are available like DOS, Windows,
Unix, and Linux etc.

Types of operating system

1. Single user operating system.
2. Multi user operating system.
3. Time sharing operating system.
4. Batch processing operating system.
5. Multi processing operating system.
6. Multi tasking operating system.
7. Multi programming operating system.

2 . Application software This software is basically designed to solve any task.

Application software worked over system software. In other words we say applica-
tion software depends on system software like word, excel. Application software
can be developed using a computer language. These are developed in high-
level languages such as COBOL, C, Visual tools etc.

3. Utility software Utilities are programs, which performs a specific function.

Utilities are part of system programs. Utility programs are generally supplied
by the computer manufacturer and also available for the call up by the operat-
ing system. This software is designed to perform any task with operating sys-
tem. Most utility software are inbuilt like scandisk, compiler, interpreter etc.
Utility program related to software maintenance, unnecessary files are cre-
ated by system and they are deleted by utility program. Example: -. Antivirus.

Translator
Translator is software. Through this we can convert any language
source code into other language. It is a mediator. It works between user
source code and machine.
A digital computer accepts digits and alphabets as input. All inputs are
translated into machine language by translator, which is understandable by
computer.

Translator can be classified into the following categories.

1. Compiler
2. Interpreter
3. Assembler

1. Compiler A compiler is program’s that reads a program and translate it

into machine code. Through this software, we convert a high level language
into machine language. Today most programming languages used compiler.
Compiler reads a whole program at a time. It occupies less space of memory
and debugging process is also very fast (check and analysis).

2. Assembler Through this software we convert the source code of assembly

language into machine language. But today this software is not in use.

3. Interpreter An interpreter functions like a compiler. It takes one statement

of program at a time and translates into machine code. Through this software
we convert high level language to machine language. This software occupies
more space of memory and debugging process is also very slow. Interpreter
is oldest translator. Advance form of translator is compiler.

Difference between compiler and interpreter

Compiler Interpreter
1 It compiles a whole program at a Interpreter read a single line at a time.
time.
2 Its debugging process is fast Its debugging process is slow
3 It shows all errors at a time. It shows errors one by one
4 It occupies less space of memory It occupies more space of memory
5 Compiler reads source code every Interpreter reads source code only
time before execution. one time at the beginning.
6 If any change is made in program it If we change anything in your program
 will not read the program. then it will read the program.

Language
Language is a system for communicating. A language consists of all the
verbal and written symbols and expressions that are used to exchange ideas
and information. In computer science, human languages are known as natu-
ral languages. Computer cannot understand natural languages. We must
communicate with computer using special computer languages.

In computer there are two types of languages.

1. High level language
2. Low level language

1. High level language

It is a famous language. It is known as user-friendly language. Because
general English words are used. This language can be run on any type of ma-
chine. It’s a modification of low- level language. We can understand program,
which are written in this language. But the execution of program is slow. Be-
cause high- level language first convert into machine language. In this lan-
guage no security is for source code. Because anyone can understand the
source code easily.
High level Compiler Machine
Language Interpreter Code

Advantages of High Level Language

1. They are easier to learn than assembly languages.
2. They require less time to write.
3. They provide better documentation.
4. They are easier to maintain.
5. A programmer skilled in writing programs in such language is not re-
stricted to using a single type of machine.

2. Low Level Language: It is an oldest language. Everyone cannot under-

stand this language because low-level language is a machine language.

(i) Machine Language: This language is not easy to understand. Because

in this language 0,1 code is used. This code is also known as binary code.
This language can’t be run on any machine (computer). It’s not a user-friendly
language.

(ii) Assembly Language: This language is developed in low -level lan-

guage. In this language mnemonic code is used. This code is in the form of
general English. These codes are basically designed for mathematical calcu-
lation like add, subtract Div. etc. This language is not used today. Assembly
language allows symbolic addressing.

ASCII
(American standard code information interchange)
Today most computers are used ASCII number code system. ASCII
code is 7-bit number system. In this number system first four bits are for num-
ber and next three numbers are for zone part. ASCII code has 0 to 255 char-
acters. In this code a to z. alphabets, 0 to 9 numbers and many special char-
acters are used.
ASCII code is used for small computers like micro & mini.

2. EBCDIC Code:
(Extended binary coded decimal information code).
In this code there are 256 characters are used. This number is of 8 bits.
First four bit for numbers and next four (bit) numbers are for zone part. This
number system is used in big computers like Macintosh, apple, super com-
puter etc.

3. BCD :
(Binary Coded Decimal)
It is an oldest number system but today this number system is not used.
This number system is basically designed for decimal number. It is 4-bit num-
ber system. In this number system each decimal digit represents four bits.

#SIGNAL
1. Analog Signal:
Analog signal’s frequency level always fluctuates so the information and data
which are received through it are not accurate. These signals are used in
telephones, radio, weather forecasting etc. These signals are in the form of
wave. Its frequency is never stable.

Wave Signal
Fluctuate frequency
1. Analog Signal
i.Periodic: In periodic signals,the distance of one signal to other is same.
ii.Aperiodic:Its distance is not same. The distance of one signal to another is
changed.
Changed Frequency
Aperiodic Signal

2. Digital Signals
These signals worked on fixed or constant frequency. Data received
from these signals are right and accurate. These signals use in calculators,
watches, computer etc. It frequency is not in the form of wave so they give
right result.

Digital Signals
Digital signal is divided into two parts.
i. Periodic: In periodic the distance of one signal to other is same.
Constant Frequency
Periodic Signal
ii. Aperiodic:Its distance is not same. The distance of one signal to an-
other is changed.
Changed Frequency
Periodic Signal

MODULATION
1.Amplitude Modulation: It is used in analog signal. Through this we can get
(calculate) amplitude value between points of two signals. We can count dis-
tance between two points like A to B, C to D or any two, points of signal.

2.Frequency Modulation: Through this we can calculate how many analog

waves are formed in a second. We can calculate how many Analog waves
are created in one second. The method is used on analog signal. It is used to
find out that frequency is not going low.

3.Phase Modulation: It is also worked on analog signal. Through this we cal-

culate degree and radian of analog signal.

Direction Of Transmission Flow

1. Simplex: It is a communication channel. Information can be send in one di-
rection. But we can’t receive data from it. So it is called one-way channel
also. For example keyboard. It is a cheapest channel.

2. Half Duplex: This communication channel is called two-way line also. In

this we can send information as well as received information. But can be
done one work at a time. Example -Hard disk/Floppy disk

3. Full Duplex: Full duplex is also a communication channel it is a costly

communication channel. It is also called two-way line channel. Data can be
sending and receive at a time in this channel. Like telephone
Sender & Receiver

COMMUNICATION SOFTWARE
Communication software: That software which is used in a network is
known as communication software, like oracle, FoxPro, MS Office etc. All
these software’s are installed in a server. That can be access in other system.
These software’s give the facility of communication.
 Example. Yahoo.com. It is not software but website. It can be access in
every computer that has Internet connection.

Communication Protocols: We need protocol for any communication in a

network. Without protocol we can’t do work in a network. There are different
types of protocols are available for each of them are working in a network.
This protocol is basically program or a set of rules. Protocols like FTP, TCP/
IP, HTTP and POP etc.

FTP: (File Transfer Protocol)

This protocol is used for transferring of files.
TCP/IP: (Transmission Control Protocol / Internet Protocol)
This protocol (TCP) is used with FTP & IP protocol. It contains the address of
working.
POP: (Post office Protocol)
This protocol is used with the electronic mail (e-mail) to upload & download
E-Mails from server.
HTTP: (hypertext Transfer Protocol)
This protocol is used to transfer hypertext (website) from server to client.

Communication Channels

1. Twisted Cable:It is a very cheapest medium of communication. In this

wires are twisted in each other. This cable is mostly used in cable lines. But in
this cable, so many times information can be destroyed because signals are
collapsed (destroyed)/ mixed in each other. Because body cover of cable is
very thin. This cable doesn’t provide security as the signals collapsed. This
cable is used in local telephone lines.

2. Fiber Optic Cable: It is a very costly cable. This cable is used in big net-
works line (convert to another). In this cable there is no possibility of loosing
of information because inside of this cable there are glass particles is used.
These glass particles help to prevent in collapsing signal. A kind of cutter is
used to cut this type of cable. This cable contains poison.

3. Coaxial Cable:
This cable is widely used in the network because this cable is cheaper
than fiber optic cable but it is costlier than twisted cable. In this cable rate of
collapsing the signal is very low because this cable used a twice packing.
One is inner packing of cable and other is outer packing of cable.

4. Serial and Parallel Communication:

This cable is fixed inside of CPU. In a serial communication we can do
only one work at a time. If we serial a data we can’t receive. If we receive the
data we can’t send. It is costly cable. We can do both work at a time. We can
send as well as receive the information. Because this cable contains two data
bus. Data bus is cable.
MODEM
Modem is a hardware component. It is called hybrid also. It is used to
connect phone lines to computer. This device coverts analog signal to digital
signals and digital signal to analog signals. When any data comes through
phone line, Modem is used to convert signals. When any signal sends from
computer to phone lines, Modem converts these signals.

Modem is divided into two parts.

i. External Modem: This modem is not fixed inside of CPU. It is connected
outside of CPU. This modem is costly because can easily shift this modem
from one location to another location and also easy to install in any computer.
Two category of modem is fax, voice.

ii. Internal Modem: This modem is fixed inside of CPU. It is fixed on mother-
board. It is not a costly modem it can’t be taken from one location to another
easily. Its speed is less than external modem.

Types Of Connection
1. Dial up: It is a program through which we can connect with Internet. In this
program telephone number is must for connection.
2. Leased Lines: It is also known as dedicated line because we can only
work with Internet.
3. ISDN: (Integrated Services Digital network).Through this line we can
send the text, voice and graphical images in form of digital signals.

Network: Network is a collection of computers connected with each other to

transfer the data from one location to another.

There are 3 types of networks:

1. LAN (Local Area Network)
2. WAN (Wide Area Network)
3. MAN (Metro Area Network)

1. LAN: This network is worked on small area like connection between com-
puters in a single room. In a building or building to building.
Topology of LAN:
1.Star topology 2.Bus topology 3.Ring topology
4.Tree topology 5.Mixed or mesh topology

(i) Star topology: In this topology all computers are connected with single
computer. In this topology one computer is called host and remaining are
nodes.
(ii). Bus topology: In this topology all the computers are connected with one
computer.

(iii). Ring topology: In this topology all the computers are connected in the
form of ring and data transmission can be possible in one direction. It is con-
nected by single cable.

(iv). Tree topology: In this topology a single computer can provide more than
one connection and only single cable is used for making a connection. This
topology works like a braches of tree.

(v). Mixed or Mesh topology: In this type of topology a single computer can
connect with so many computers. This topology is used to run, typical net-
work. This topology is used in WAN man also. It is very cheapest topology.

2. WAN This network works between the cities or countries. WAN is possible
with two methods. 1.Through satellite 2.Through telephone line.

3. MAN This network is worked between metro cities.

COMPONENTS OF LAN
1. Media: Through this we can work different types of activities like to watch
movies, songs, access the Internet and print any documents.
2. NIC (Network interface card) This card is fixed inside of CPU without this
card no computer can be connected with other. It is also called Ethernet card.
It is necessary to install in computer then we can connect systems.
3. NOS: (Network operating system) That operating system through which
we can connect more than one system and can make a network is called as
network operating system, like windows NT, Unix, Linux, novel NetWare (use
to join).
4. HUB: It is a hardware network component. This component is used in start
topology. It is also called workstation with the help of hub we can connect
node and services connections.
5. Repeater:This component is worked on single network. It is used to in-
crease the frequency of signals.It increases those frequencies which are low
there are two types of repeater. 1.Amplifier 2.Retransmit signal device
6.Bridge: It is a network component. Bridge is used to connect two different
types of network but it is compulsory that network operating system must be
same type and software should be same of both network. This device is help-
ful to transfer data from one network to other.
7. Router: Router is also a network component. Through it two different net-
works are connected to each other but in the network operating system must
be same but it is not compulsory that software should be same. In other
words we say that router works with two different protocols.
8. Gateway: It is a network component. It is most powerful component is
used to connect two different type of networks & Both networks with different
operating system and software likes windows NT, Unix, Transfer information
from one to another.
LASER PRINTER
Hardware Components
1.Drum 2.Toner -It contains ink. 3.Mirror (laser beams reflect) 4.Laser beam
Inkjet Printer :
It has small bottles of ink. Each has small hole (nogle) through which ink sup-
plied for printing. The bottle is known as cartridge.
Laser Inkjet
1. Cost Less costly than laser
2. Quality sharp Quality is good but poor than laser
3. Black & white Colour & B/W print
(Latest an print)
4. Page prints Line prints
5. It prints character It Print in the form of dots.
6. Speed fast slow.
Impact Printer Non Impact Printer
1. Impact printers head strikes Non-impact printers head doesn’t strike.
while printing
2. Impact printers produced sound It doesn’t produce sound.
while printing
3. Its printing speed is slow. Its printing speed is fast.
4. Impact printers quality is not Its printing quality is good.
good
5. It prints a line at a time. It prints line wise and page wise also. Inkjet
-line laser- page.
6. It prints black & white. It can print both colour & b/w
7. Exa. Drum printer Daisy wheel, Exa. Inkjet, Laser Printer.
Dot matrix
8. Its maintenance cost is less. Its maintenance cost is more.
9. Impact printer can print graphi- Non-impact printer can print graphically
cally but quality isn’t good. with good quality.

10. It used ribbon for printing. It has cartridge or toner for printing pur-
pose.
Super Computer & Structure
1. Hard disk
2. RAM
3. Wide network – can connect 500 to 1000 computers. However normally
250 computers.
4. Super computer’s memory is too large comparatively to normal.
5. Super computer’s size is very big. It has no portability. Normal compa-
nies are portable.
6. Super computer can work on both Analog and Digital signal.
Normal computer works on either analog or digital signal.
7. Super computers microprocessor is very powerful than other computer.
8. Super computer is not a general-purpose computer. However all other

High Level Language Low Level Language

1. High-level language work on Eng- Low-level language. /machine language
lish.
2. High-level language isn’t machine Low-level language is machine depen-
dependent. dent language. It can’t be run on other
machine.
3. High level is an understandable lan- Low-level language is not understand-
guage. able.
4. High-level languages execution is Its execution is fast. Because it isn’t
slow because it has to convert to in translated.
machine language.
5. High-level language doesn’t provide Low level provides source security.
security.
6. Error can be detected easily. In low-level language errors can’t detect
easily.
7. In High-level language compiler & In assembly language assembler is
interpreter are used. used.

Application software System software

1. Application software doesn’t use for sys- System software is designed for system
tem operating. operating
2. It is essential for user not for system. System software is essential for computer.
3. Application software can’t work without System software is do work without appli-
system software. cation software.
4. Application software is Word, Excel etc. System softwares are DOS, Windows,
Unix, and Linux.
5. Application software’s working is limited. System software’s working is unlimited.
6. Many people can use it. It has single user & multi user facility.
7. Application software can’t create net- System software is used/or can create net-
working. working.
8. It doesn’t provide tool for system mainte- System software provides system tools for
nance. system maintenance.

Batch Processing Time Sharing

1. Batch processing depends on time-shar- Time-sharing doesn’t depend.
ing.
2. One process executed in one time. Time-sharing processes many
process at a time.
3. Batch processing arranges a work in the In time sharing work, doesn’t ar-
form of a batch. range.
4. Batch processing work on FIFO. It doesn’t work on FIFO.
5. Batch processing works for a part if sys- Time-sharing works for whole
tem such as printing. system.

Multi Programming Multi Processing

1. Multi programming allows working Multi processing allows working on
on only program. any process or program like calcula-
tions.
2. Multi programming is performed Multi processing is performed on one
on many computers. computer and many computers.
3. Programs can be made in multi Programs can’t create in multi pro-
programming. cessing.
4. Multi programming is stored in an Multi processing is stored in server.
individual system .
5. Multi programming depends on Multi processing depends on time-
multi processing. sharing.

Sequential Method Direct Storage Method

1. Sequential tool take too much time to retrieve Direct storage takes less time in re-
data. trieving.
2. Ex. sequential magnetic tap Ex. Hard disk, Floppy, disk CD.
3. Sequential storage stores the information in se- In direct storage information stores
 quence step by step. anywhere.
4. Data can’t be retrieved sequentially. Data can be retrieve from any-
where directly.
5. Sequential method is used on sequential stor- Direct storage is used on optical
age device. disk type device.
6. Sequential doesn’t use fat. Direct storage used fat for storing &
retrieving.