Introduction of Computer
Definition
of Computer: Computer
is an electronic device which takes the input value from user, store in memory
and gave a correct and meaningful result (or output).
INPUT --> PROCESS --> OUTPUT
Parts
of Computer: There
are two parts of computer-
1) Hardware 2) Software
1) Hardware:
The physical parts of computer are
known as hardware. Some such parts are micro processor, hard disc, printer,
monitor etc.
The
hardware devices are divided into three categories-
1.1) C. P. U 1.2) Input & output Device 1.3) Secondary Memory
1.1) C. P. U.:
The full name of CPU is Central
Processor Unit. It is the brain of computer. The primary function of CPU is to
load a computer and control input and output devices. All work of computer is
controlled by this part that is CPU.
The
primary function is also divided into three parts-
1.1.1) Primary Memory 1.1.2) A. L. U. 1.1.3) C. U.
1.1.1)
Primary Memory: Primary
memory is a storage unit of computer. Primary memory is a small and relatively
fast storage unit. It store data and instructions that are being correctly use
by the computer.
Primary
memory is divided into two parts-
1.1.1.1)
RAM: The full name of
RAM is Random Access Memory. It is a temporary type of memory. User can work in
RAM. It retains the stored information as long as it is supplied with power
supply. When power supply is switched off or interrupted, the stored
information in the RAM is lost. RAMs are various capacities are available, for
example 256 MB, 512 MB, 1 GB, 2 GB and 4 GB.
1.1.1.2)
ROM: The full name of
ROM is Read Only Memory. It is a permanent type of memory. User can not work in
ROM.
PROM : Programmable Read Only Memory
EPROM : Erasable Programmable Read Only
Memory
EEPROM : Electrically Erasable Programmable Read
Only Memory
1.1.2)
A. L. U.: The full
name of ALU is Arithmetic and Logic Unit. It is responsible for all mathematical
and logical work. The data and instructions, stored in the primary memory prior
to processing, are transferred to the ALU where processing takes place.
Results
generated in the ALU are transferred to the primary memory. After completion of
processing, the final result available in the primary memory, are sent to an
output device, such as monitor.
1.1.3)
C. U.: The full name
of CU is Control Unit. It is control all throw of signals from various part of
computer. It is able to maintain order and direct the working of the entire
computer system. Although it does not perform any processing on the data, the
control unit acts as the central nervous system for all other components of the
computer. It coordinates the entire jobs done by the computer system.
1.2) Input & Output Devices:
Input Devices:
Data and Instructions
are entered into a computer through input devices. An input device first
converts desired input data and instructions into a suitable binary form (0, 1)
and then feed it into the CPU.
There
are some common input devices such as-
1)
Keyboard: Programs
and data are entered into a computer through a keyboard which is attached to a
computer. A keyboard is similar to the keyboard of a typewriter. It contains
alphabets, digits, special characters, function keys and some control keys.
2)
Mouse: A mouse is a
pointing device. It is held in one hand and moved across a flat surface. The
mouse can also be used to draw sketches, diagrams etc. on the monitor screen. The
mouse is also used to edit text.
3)
Light Pen: A light
pen is a pointing device. It is used to select a displayed menu option on the
monitor screen. It is a photosensitive pen-like device. With the help of light
pen we can draw any picture on the monitor screen when its tip touches the
screen.
4)
Scanner: A scanner is
a hardware device used to scan text or images into the computer. Sometimes the
information, picture or text that is available on paper is needed on the
computer.
5)
Joystick: A joystick
is also a pointing device. It is used to move the cursor position on a monitor
screen. Its function is similar to that of a mouse and is used for playing
games.
6)
Web Camera: A web
camera allows a computer to accept input just by focusing on an object. The
camera is focused on the input object to take a picture of the object. Picture
so taken can be transferred over computer network to a distant place.
7)
OMR: The full name of
OMR is Optical Mark Reader. OMRs are special scanners used for recognizing a
pre-specified type of mark made by pencil or pen. For example, in the objective
test paper of DOEACC, you mark your answers on a special sheet by darkening a
small square, using a pen or pencil.
8)
Bar Code Reader: Bar
code readers are special devices used to read bar coded data. Bar code is a
specialized code use for fast identification of items. It consists of a series
of small lines, known as bars.
9)
MICR: The full name
of MICR is Magnetic Ink Character Recognition. MICR detects the special encoded
characters on bank cheques and deposit slips. After detecting the encoded
characters, the MICR converts them into digital data for the computer.
10)
Card Reader: A card
reader is a device that reads memory cards. A memory card is a storage medium
made of thick paper card that holds data in the form of punched holes.
11)
Video Camera: A video
camera is a camera that takes continuous pictures and generates a digital or
analog signal for display on a monitor.
12)
Trackball: A
trackball is also a pointing device and contains a ball which can rotate in any
direction. The user spins the ball in different directions to move the cursor
on the monitor. This type of pointing device is normally used in a laptop
computer.
Output Devices: Output devices are those devices of
computer system that supplies information or results either in form of hardcopy
(printer) or softcopy (monitor). Some of the common output devices are as
following:
1)
Monitor: A monitor is
very similar to a television. It shows text or picture in color or black &
white, depending on the type of monitor. Whatever you type on the keyboard, you
can see it on the monitor.
VDU – Visual Display Unit
CRT – Cathode Ray Tube
TFT-LCD – Thin Film Transistor-Liquid
Crystal Display
LED – Light Emitting Diode
2)
Printer: Printers are
the most popular output devices. They provide information in a permanent
readable form. They produce printed outputs of results, programs and data.
Based on their function, the printers are available in three different types:
2.1)
Dot Matrix Printer: Dot
Matrix Printer is one of the oldest printers, yet in use. It is direct contact
to print medium (paper). It is a low cost printer and the print quality is very
low. It is used in bill printing, ticket printing, etc.
2.2)
Inkjet Printer: The
inkjet printer contains ink nozzles. In this type of printers, continuous
stream of ink-drops is used. It is also available in colored versions.
2.3)
Laser Printer: Laser
Printer is expensive and very good quality printer. They print one page at a
time. These printers use laser or other light source to produce an image.
1.3) Secondary Memory:
You
cannot store data in the main memory of a computer permanently. Firstly,
because it is very expensive and secondly its contents are erased when the
computer is turned off. For permanent storage of data, you have to use
secondary memory or storage device such as floppy disk, hard disk, compact disk
(CD), etc. These are also called external storage device.
1.3.1)
Hard Disk: A hard
disk is a device used for mass storage of data. The data stored on a hard disk
can be retrieved at a very fast speed, being a direct address device. Unlike
floppies, CDs, zip disks, etc. You cannot easily remove hard disk from a
computer.
1.3.2)
Floppy Disk: A floppy
disk also called a disk or diskette is a removable storage disk used for
storing data. It is called a floppy disk because the round film inside the
disk’s plastic shell is flexible (floppy).
1.3.3)
CD-Rom (Compact Disk-Read Only Memory): It is an optical Read Only Memory (ROM). A CD-ROM has a
shelf life of more than 40 years. A CD-ROM can store about 700 MB data, (about
800 floppies).
1.3.4)
DVD: DVD stands for
digital video disk or digital versatile disk. DVD disks provide high video
resolution and high quality of sound. A DVD can store about 4.7 GB data.
1.3.5)
Pen Drive: USB
(Universal Serial Bus) flash drive or pen drive is typically small,
lightweight, removable and rewritable. It is a flash memory card that plugs
into the computer’s USB port. It emulates a small disk drive and allows data to
be easily transferred from one computer to another computer.
1.3.6)
Memory Card: A memory card is a storage medium made of thick
paper card that holds data in the form of punched holes. The holes are punched
into the card by a keypunch machine or card punch peripheral device connected
to a computer.
2.2)
Application Software: Application software
is a set of one or more programs, which solves a specific problem, or does a
specific task. For example, payroll processing software, examination results
processing software, railway/airline reservation software and computer games
software are application software.
2) Software:
Software
is a set of computer programs. A program is the name given to a list of
instructions or statements that direct the computer to perform the required
task. Software is what we see on the computer’s screen. We cannot touch it
physically, but only see it. The programs and files stored on the computer are
called software.
Software
(Programs) is of the following types:
2.1) System Software 2.2)
Application Software
Software
Application Software System
Software
User
Written Readymade Assemblers Compilers
Loaders Linkers Operating
Software Software
System
2.1)
System Software:
System software or system packages are set of one or more programs that are
basically designed to control the operation of a computer system. They are
general programs written to assist users in the use of the computer system by
performing tasks, such as controlling hardware, moving data into and out of a
computer and all the other steps in executing the application program. In
general, system packages control the following:
(a) Running the other software
packages.
(b) Communicating with peripheral
devices such as printers, hard disk, etc.
(c) Monitoring the use of various
hardware resources such as memory, peripherals, CPU, etc.
System
software thus makes the operation of the computer system more effective and
efficient.
