Input & Output Devices
Keyboard
Mouse
Scanner
Output Devices
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Input Devices
A computer is only useful when it is able to communicate with the external environment.
When you work with the computer you feed your data and instructions through some devices
to the computer. These devices are called
Input devices .
This is the standard input device attached to all computers. The layout of keyboard is just
like the traditional typewriter of the type
QWERTY . It also contains some
extra command
keys and
function keys . You have to press correct combination of keys to
input data. The computer can recognise the
electrical signals corresponding to the
correct key combination and processing is done accordingly.
Mouse is an input device that is used with your personal computer.
It rolls on a
small ball and has two or three buttons on the top. When you roll the
mouse across a flat surface the screen censors the mouse in the direction of mouse movement.
The cursor moves very fast with mouse giving you more freedom to work in any direction.
It is easier and faster to move through a mouse.
The keyboard can input only text through keys provided in it. If we want to input a picture the
keyboard cannot do that. Scanner is an optical device that can input any
graphical matter and
display it back. The common optical scanner devices are Magnetic Ink Character Recognition
(MICR), Optical Mark Reader (OMR) and Optical Character Reader (OCR).
1) Magnetic Ink Character Recognition (MICR) - This is widely used
by
banks to process large volumes of
cheques and
drafts . Cheques are put inside the MICR.
As they enter the reading unit the cheques pass through the magnetic field which causes
the read head to recognise the character of the cheques.
2) Optical Mark Reader (OMR) - This technique is used when students
have appeared in
objective type tests and they had to mark their answer by darkening a
square
or
circular space by pencil. These answer sheets are directly fed to a computer for
grading where OMR is used.
3) Optical Character Recognition (OCR) - This technique unites
the
direct reading of any printed character. Suppose you have a set of hand written
characters on a piece of paper. You put it inside the scanner of the computer.
This pattern is
compared with a site of patterns stored inside the computer.
Whichever pattern is matched is called a
character read . Patterns that cannot
be identified are rejected. OCRs are expensive though better the MICR.
Computer after processing, gives output through other devices called output devices.
Visual Display Unit
The most popular input/output device is the Visual Display Unit (VDU). It is also called the
monitor.
A Keyboard is used to input data and Monitor is used to display the input data and to
receive massages from the computer.
A monitor has its own box which is separated from
the main computer system and is connected to the computer by cable. In some systems
it is compact with the system unit. It can be
color or
monochrome .
Speaker
A speaker gives you sound output from your computer. Some speakers are
built into the computer and some are separate.
Printer
It is an important output device which can be used to get a printed copy of the
processed text or result on paper. There are different types of printers that are
designed for different types of applications.
Depending on their speed and approach
of printing, printers are classified as
impact and
non-impact printers.
Impact printers use the familiar typewriter approach of hammering a typeface against
the paper and inked ribbon.
Dot-matrix printers are of this type.
Non-impact printers do not hit or impact a ribbon to print. They use
electro-static
chemicals and
ink-jet technologies .
Laser printers and
Ink-jet printers are of this type.
This type of printers can produce
color printing and
elaborate graphics .
