INTRODUCTION
The word computer has been derived from
the Latin word ‘COMPUTARE’, which
means to compute or to calculate.
A computer can be defined as an
electronic device used to calculate and
manipulate the data (i.e. input) and
generates an output in the form of useful
information by following a set of
procedural instructions.
British scientist Charles Babbage is
considered as the Father of Computer.
He invented the first mechanical
computer in early 19th century and
further in 1833, he conceived a automatic
analytical engine for performing
arithmetic functions.
Alan Mathison Turing is widely regarded as
the Father of Modern Computers or Father
of theortical computer science and Artificial
Intelligence (AI).
Characteristics of Computer
● Speed ● Accuracy
● Diligence ● Versatility
Applications of Computer
● Education
● Hospitals
● Business
● Weather forecasting
● Entertainment
● Organisations
Types of Computer
Computer can be classified on three
basis
On the Basis of Functions
● Analog Computers This is a type
of computer that reads data using
measurement and some program
scale. It calculates by measuring
continuous changes in the physical
quantities. e.g. Mechanical
integrators, nomogram,
speedometer etc.
● Digital Computers This is a
computer that performs calculations
and logical operations with
quantities represented as binary
digits. e.g. Desktop, mainframe etc.
● Hybrid Computers These
computers are the combination of
both analog and digital computers. It
works by measuring quantity and
calculating logical operations. e.g.
ECG monitors, HRS-100 etc.
On the Basis of Purposes
● General Purpose Computers This
type of computers are designed in
order to work in all environments.
They are versatile computers but are
not efficient and also consume a
large amount of time in generating
the results. e.g. ENIAC, desktops
etc.
● Special Purpose Computers They
are designed to perform only a
specified task. They are not versatile
and their speed and size depends on
the task. They are efficient and
consume less time in generating
results. e.g. ATM, aircraft controllers
etc.
On the Basis of Size and
Capability
● Micro Computers It is a digital
computer used by individuals and is
also considered as an acronym for
Personal Computers (PCs). They are
small in size. They are usually used
at homes, in schools and offices etc.
e.g. Laptop, Palmtop, Notebook,
Desktop etc.
● Mini Computers This type of computers
are more powerful than micro computers,
but less powerful than mainframe
computers. They are also termed as
mid-range computers.
● It is a multiprocessing system capable of
supporting 4 to about 200 users
simultaneously. e.g. IBM mid range
computers, K-202, SDS-92 etc.
● Mainframe Computers It is a very large
computer and is used for handling major
applications in large business organisations.
They can also be used as centralised
computers with several terminal users
connected to it. They can contain large
databases and are also known as super
servers.
● They can handle huge amount of
input/output (I/O) operations at the same
time. They are very expensive. e.g. Fujitsu’s
ICL VME, Hitachi’s Z800 etc.
● Super Computers It can be defined as the
most powerful computer in terms of
performance and storage capacity. They are
highly expensive and are employed for
specialised applications such as for weather
forecasting, several scientific researches etc.
● NASA (National Aeronautics for Space
Administration) uses super computers for
launching space shuttles, controlling them
and for space exploration purpose.
● PARAM is the first super computer in India.
It is a series of gigaflops developed by the
Centre of Development of Advanced
Computing (C-DAC), Pune.
Components of Computer
The computer system comprises of the
following four main components
1. Input Unit
It consists of those devices through which
user can enter the data into a computer. It
links a computer to the external
environment. It translates the data into
computers understandable form. Some input
devices are
● Keyboard is used to enter data or
information, which may be in numeric
form or alphabetical form, in a computer
system.
● Mouse is a pointing device which provides
a means to input data and commands in
graphic form by selecting through moving
an arrow called pointer.
● Trackball is another pointing device which
is an alternative to a mouse.
● Joystick is an input device that moves in all
directions and controls the movement of
the cursor.
● Scanner is an optical input device and
uses light as an input source to convert an
image into an electronic form that can be
stored on the computer.
● Touch Screen is an electronic visual
display that can detect the presence and
location of a touch within the display area.
2. Output Unit
This unit contains those devices that
provide the desired output (results) in
the human acceptable format.
Some output devices are
● Monitor is also known as Visual Display
Unit (VDU). The monitor is provided
along with the computer to view the
display result. The popular types of
monitor are
◆ LCD (Liquid Crystal Display), a special
type of liquid is sandwiched between
two plates. It is a thin, flat and light
weight screen made up of any number
of colour or monochrome pixels
arranged in front of a light source.
◆ LED (Liquid/Light Emitted Diode) is
an electronic device that emits light
when electrical current is passed
through it.
◆ TFT (Thin Film Transistor) is a LCD
with active-matrix displays, each pixel
is controlled by one to four transistors
that can make the screen faster,
brighter, more colorful than
passive-matrix and capable of being
viewed at different angles.
◆ 3-D Monitors describe an image that
provides the perception of length.
When 3-D images are made interactive
then user feel involved with the scene,
and this experience is called virtual
reality.
● Printer prints information and data
from the computer onto a paper. It can
print documents in colour as well as in
black and white.
● Plotter is a special kind of output
channel, like a printer, that produces
images on paper. They are mainly used
to produce large drawings or images.
● Speaker is an output device that
receives sound in the form of electric
current. It needs a sound card
connected to a CPU, that generates
sound.
3. CPU (Central Processing
Unit)
CPU is considered as the ‘Brain of
Computer’. It is responsible for all the
manipulations and processing of the
data provided to the computer. It is
further categorised basically into two
main components
● Arithmetic Logical Unit (ALU) This
unit performs both arithmetical and
logical operations. Arithmetic opera-
tions involves addition, subtraction,
multiplication, division etc and the
logical operations involves AND, OR,
NOT, NOR, NAND etc.
● Control Unit (CU) It is an important
part that instructs, maintains and
controls the flow of information but
does not store the data. It tells the
memory, ALU and I/O devices that
how they have to respond to the
program’s instructions.
4. Memory Unit
This unit stores the data and
instructions, intermediate results or the
processed data and thus, provides the
relevant information whenever required
by the other units of computer.
It consists of two types
● Primary Memory It is considered to
be the main memory of computer that
stores the data which is currently in
use by the computer.
● Types of Primary Memory:
◆ RAM (Random Access Memory) is a
volatile memory, which losses the data
when the power gets switched OFF.
There are basically two types of RAM:
Static RAM and Dynamic RAM.
◆ ROM (Read Only Memory) is a non-
volatile memory, which retains the data even
when the power gets switched OFF.
◆ Program and data that cannot be altered are
stored in ROM. There are basically three
types of ROM: Programmable ROM(PROM),
Erasable PROM(EPROM) and Electrically
EPROM(EEPROM).
● Secondary Memory The computer system
uses secondary memory to store data,
program instruction and information. It
stores the data permanently. User can
access or retrieve the data whenever
required. Types of Secondary Memory:
◆ Magnetic Tape (sequential access)
◆ Magnetic Disk (Floppy Disk, Hard Disk)
◆ Optical Disc (CD, DVD, Blu-ray Disc)
◆ Solid State drive (Flash drive, SD cards)
Cache Memory
It is a type of memory used to hold the frequently
used data. It acts as a buffer between the CPU
and the main memory. It consumes less access
time as compared to main memory and thus, is
used to match up the speed of fast running
processor.
Registers
These are defined as the special memory units
used by the CPU to speed up the rate of accessing
information. There are some special type of
registers used for specific work.
e.g. Program Counter (PC) is used to hold the
address of the next instruction for execution.
Some other examples are Accumulator, Memory
Buffer Register (MBR), Instruction Register (IR) etc.
Hardware
It can be defined as the physical components
of a computer i.e. the parts that can be seen
and touched.
The four main categories of hardware are
● Input devices e.g. keyboard, mouse etc.
● Outputdevicese.g.printer,monitoretc.
● Storage devices e.g. hard disk, floppy disk etc.
● Processing devices e.g. CPU etc.
Software
The term software can be defined as the set of
programs and procedures that enable a
computer to perform a specific task or to
process the information. Software can be
classified into three types :
System Software
It is a set of one or more programs designed
to control the operations of a computer
system including hardware components
and implementations of application
software.
Types of System Software are
● Operating System It is a system
software, consisting of an integrated set
of programs that controls computer
resources (CPU, memory, I/O devices,
etc) and provides common services for
efficient execution of various application
software.
● Language Translator It helps in]
converting programming languages to
machine language. There are three kinds
of language translator
◆ Assembler It converts program written in
assembly language into machine
language.
◆ Interpreter It converts a high level
language into machine language by
converting it line by line.
◆ Complier It also converts high level
language program into machine language
at one go.
