What is computer?
Computer is an electronic devices which accepts the data & process it by the pre desired software and gives the results.
Advantage of computer
A machine is said to be automatic, if it works by itself
human intervention. Computer is a
automatic machine because one started on a job, they carry on until the job is finished, normally
A computer is a very fast device. It can perform in a few seconds, the amount of work
that a human being
can do in an entire year.
In addition to bei
ng very fast, computer are very
accurate. The accuracy of a computer is
and degree of accuracy of a particular computer depends upon
Unlike human beings, a computer is free from monotony, tiredness and lack of concentration. It can
continuously work for hours, without
creating any error and without grumbling.
Versatility is one of the most wonderful things about th
e computer. On e moment, it is preparing
the results of an examination, the next moment, it is busy preparing electricity bills, and in between, it may be
helping an office secretary to trace an important letter in second.
Power of Remembering:
A computer can store and recall any amount of information because of its secondary
The Computer Generations
First Generation (1942
The characteristic features of first generation computers are as follow:
They were fastest
calculating device of their time
There were to bulky in size, require large rooms for installation.
Thousands of vacuum tubes , which were used, emitted large amount of heat and burnt out frequently.
Hence, the rooms/areas in which these computer were loc
ated had to be properly air
Each Vacuum tube consumed about half a watt of power. The power consumption of these computer
was very high.
Due to the law time between failures, these computer require almost constant maintance.
These computer we
re difficult to program and use. They had limited comm
The UNIVAC and
computers are examples of first
generation computing devices.
Second Generation (1955
electronic switching device, called transistor , was invented at Bell Laboratories in 1947 by John Bardeen,
Williand Shockly, and Walter Brattain. Transistor soon proved to be a better electronic switching device than the
stic feature of second
generation computers are as follows:
They were more than ten times faster than the first generation computer.
were used in this computer.
They were much smaller than first generation computers, requiring smaller space.
ume much less power than the first
They had faster and large primary and less prone to hardware failures than the first
They had faster and large primary and secondary storage as compared to first
They were much easier to program and use than the first generation computer. Hence. They had wider
Third Generation (1964
In 1958, Jack St. Clair Kilby and Robert Noyce invented the first integrated circuit (IC).
It circuit consisting of
several electronic components like transistor, resistors, and capacitors grown on a single chip of silicon,
eliminating wired interconnection between components.
The third generation was characterized by computer built using inte
the earlier once use Small Scale
Integration(SSI) technology and the later ones used Medium Scale Integration(MSI) technology.
The characters features of third
generation computers are as follows:
They were much more powerful than the
computers. They were capable of performing about
They were much
requiring smaller space.
They consumed much less power than the second generati
They were more reliable and less prone to hardware failures than the second generation computers.
Hence the maintenance cost was much lawer.
They had faster and large primary and secondary storage as compared to second generation
ndardization of high level programming languages allowed programs written for one computer to
be easily ported to and executed on another computer.
Time sharing operating system allowed interactive usage and simultaneous use of these systems by a
mbers of users.
Fourth Generation (1975
brought the fourth generation of computers, as thousands of integrated circuits were built onto a single
silicon chip. What in
the first generation filled an entire room could now fit in the palm of the hand. The Intel 4004 chip,
developed in 1971, located all the components of the computer
central processing unit
ry to input/output
on a single chip
The characters features of
generation computers are as follows:
The PCs were smaller and cheaper than the mainframes or minicomputers of the third generaton.
They consumed much less power than the third
They were more reliable and less prone to hardware failures than the second
They had faster and large primary and secondary storage as compared to second generation computer.
Standardization of high level progra
mming languages allowed programs written for one computer to be easily ported
to and executed on another computer.
Fifth Generation computer
Fifth generation computing devices, based on
, are still in development, though there are
, such as
, that are being used today. The use of
superconductors is helping to make artificial intelligence a reality.
will radically change
the face of computers in years to come.
The characters features of
generation computers are as follows:
Portable PCs (called notebook computers) are much
and handy than the PCs of the fourth generation
The desktop PCs and worksta
tion are several times more powerful than the PCs of the fourth generation.
They consume much less power than their predecessors.
They are totally general purpose machine.
Use of standard high
level programming languages allows programs written for one c
omputer to be easily
protected to and executed on another computer.
Newer and more powerful application, including multimedia application, makes the system more useful in
Classification of Computers
Depending upon their speed and
memory size, computers are classified into following four main groups.
Supercomputer is the most powerful and fastest, and also very expensive. It was developed in
1980s. It is used
to process large amount of data and to solve the complicated scientific problems. It can perform more than one
trillions calculations per second. It has large number of processors connected parallel. Supercomputer are
mainly used for:
Nuclear energy research.
To control industrial units.
The examples of supercomputers are CRAY
2, Control Data CYBER 205 and ETA A
2. Mainframe Computers
ters are also large
scale computers but supercomputers are larger than mainframe. These are
also very expensive. The mainframe computer specially requires a very large clean room with air
This makes it very expensive to buy and operate. It can
support a large number of various equipments. It also
has multiple processors. Large mainframe systems can handle the input and output requirements of several
thousand of users. For example, IBM, S/390 mainframe can support 50,000 users simultaneously.
These are smaller in size, have lower processing speed and also have lower cost than mainframe. These
computers are known as minicomputers because of their small size as compared to other computers at that time.
The capabilities of a minic
omputer are between mainframe and personal computer. These computers are also
The minicomputers are used in business, education and many other government departments
The first minicomputer was introduced in the mid
1960s by D
igital Equipment Corporation (DEC).
The microcomputers are also known as personal computers or simply PCs. Microprocessor is used in this type
of computer. These are very small in size and cost. The IBM’s first microcomputer was designed
in 1981 and
was named as IBM
Personal computers are available in two models. These are:
A desktop personal computer is most popular model of personal computer. The system unit of the desktop
personal computer can lie flat on the
desk or table. In desktop personal computer, the monitor is usually placed
on the system unit.
Another model of the personal computer is known as tower personal computer. The system unit of the tower PC
is vertically placed on the desk of table. Usually
the system unit of the tower model is placed on the floor to
make desk space free and user can place other devices such as printer, scanner etc. on the desktop. Today
computer tables are available which are specially designed for this purpose. The tower mo
dels are mostly used
at homes and offices.
Microcomputer are further divided into following categories.
1. Laptop computer
Laptop computer is also known as notebook computer. It is small size
11 inch notebook computer and
can fit inside a briefcase. The laptop computer is operated on a special battery and it does not have to be
plugged in like desktop computer. The laptop computer is portable and fully functional microcomputer. It is
stly used during journey. It can be used on your lap in an airplane. It is because it is referred to as laptop
Workstations are special single user computers having the same features as personal computer but have the
peed equivalent to minicomputer or mainframe computer. A workstation computer can be fitted on
a desktop. Scientists, engineers, architects and graphic designe
rs mostly use these computers.
3. Network computers
Network computers are also version of person
al computers having less processing power, memory and storage.
These are specially designed as terminals for network environment. Some types of network computers have no
storage. The network computers are designed for network, Internet or Intranet for data
entry or to access data on
4. handheld computer
In the mid 1990s, many new types of small personal computing devices have been introduced and these are
referred to as handheld computers. These computers are also referred to as Palmt
op Computers. The handheld
computers sometimes called Mini
Notebook Computers. The type of computer is named as handheld computer
because it can fit in one hand while you can operate it with the other hand. Because of its reduced size, the
screen of handhe
ld computer is quite small. Similarly it also has small keyboard. The handheld computers are
preferred by business traveler. The examples of handheld computers are:
Personal Digital Assistance
H/PC Pro devices
1. Personal Digital Assist
The PDA is one of the more popular lightweight mobile devices in use today. A PDA provides special functions
such as taking notes, organizing telephone numbers and addresses.
2. Cellular phones
A cellular phone is a web
based telephone having
features of analog and digital devices. It is also referred to as
Smart Phone. In addition to basic phone capabilities, a cellular phone also provides the functions to receive and
mails & faxes and to access the Internet.
3. H/PC Pro Devices
Pro dive is new development in handheld technology. These systems are larger than PDAs but they are
not quite as large as typical notebook PCs. These devices have features between PDAs and notebook PCs. The
H/PC Pro device includes a full
size keyboard but
it does not include disk. These systems also have RAM with
very low storage capacity and slow speed of processor.
Components of a Computer
The components of a computer are classified into the two main categories
hardware and software
Hardware Refers to objects that you can actually touch, like disks, disk drives, display screens, keyboards, printers,
boards, and chips. In contrast, software is untouchable. Software exists as ideas, concepts, and symbols,
but it has no
The hardware of a typical computer system, irrespective of its size, consists of the following
Types of Hardware Parts
Central Processing Unit
Memory and Storage devices
Display and output
Central Processing Unit (CPU)
Central Processing Unit or processor, the
is essentially the “brains” of your computer.
The CPU may be a single silicon chip or a series of chips. A chip contains thousands of electronic switching circuits.
CPU performs arithmetic and logical calculations and controls the operations of other parts of the computer.
Memory and Storage Devices
Computer Memory, also known as internal storage device, consists of silicon chips that are directly linked to
here are two kinds of memory
Contains basic instructions of the computer stored permanently
In RAM the
computer copies and keeps
. The word RAM is often associated with
volatile types of
memory where the information is lost after the power is switched off
In order to store user programs and data permanently or as long as user wants, computers use (external) storage
The common storage devices used in personal computers are:
These are disks, fixed inside the cabinet, used for storing (read and write) very large
amounts of information. Typical sizes are about 40,80,120,160,and much more….
Used by means of floppy disk drive(s) attached to
the computer. Floppy disks in
normal use today store about 800 KB or 1.4 MB of data
read and write.
Used by means of CD
ROM drive(s). Standard capacity is about 600 MB of data
While a hard disc is fixed to the computer, floppy disks
ROMs are removable and can be used to
USB flash drive
data storage device
integrated with a
interface. USB flash drives are typically removable and
rewritable, much smaller than a
, and most weigh less than 1
is a removable
format, launched by
in October 1998,
and is also used in general to describe the whole family of
Measuring Unit of Data in the computer
1 Kilo Byte
1024 Kilo Byte
1 Mega Byte
1024 Mega Byte
1 Giga Byte
1024 Giga Byte
1 Tera Byte
provide data and control signals to an information processing system.
make up the hardware interface
Common used input device are
Used to enter text data
In computing, a
is typewriter keyboard, which uses an arrangement of buttons or keys, to act as mechanical
levers or electronic switches.
: Used to point and click at any location on the computer’s video display screen. Normally a mouse will have two
or three but
: Similar functionality as mouse
Used to point or sketch directly on the screen.
: To scan (input) images
: To capture pictures directly.
Display and Output Devices
a device that displ
ays images or symbols generated by computers
It is the main output device of a computer. It displays text as well as pictures in black and white or color.
The monitor screen consists of an array of tiny dots called
(picture elements). Typical sizes of this
array of pixels are
640 by 480
800 by 600
1024 by 768
. This is also referred as the resolution.
Another output device to which the computer can directly send the data to obtain hard copy
printouts of the results.
is a sequence of instructions written to perform a specified task for
a computer. A computer requires progr
ams to function, typically executing the program's instructions in a central
is the collection of computer programs and related data that provide
the instructions telling a computer what to do
Types of software
Practical computer systems divide software systems into three major classes
system software, programming
software and application software
System software helps run the computer hardware and computer system. It includes a combination
Programming software usually provides tools to assist a programmer in writing computer programs, and
software using different programming languages in
a more convenient way. The tools include:
pplication software offers different function based on users and the area it
developed for some certain purpose, which either can be a certain program or a collection of some programmes,
such as a graphic browser or the data base management system. Typical applications include:
is a computer program that can copy itself and infect a computer.
program or piece of code
that is loaded onto your computer without your knowledge and runs against your wishes. Viruses can also replicate
themselves. All computer viruses are manmade.
Types of Virus
There are six broad categories or types of computer vir
1. Boot Sector Virus
2. File Infection Virus
3. Multipartite Virus
4. Network Virus
6. Macro Virus
Name of Some Viruses
, Comet Cursor,
, Internet Optimizer,
Antivirus software is a computer program that detects, prevents, and takes action to disarm or remove malicious software
programs, such as viruses and worms. You can help protect your computer against viruses by using antivirus software.
f few Anti Virus programs.
Quick Heal Antivirus