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. Similarly computer after processing, gives output through other devices called output devices.
For a particular
application one form of device is more desirable compared to others. We will
discuss various types of I/O devices that are used for different types of
applications. They are also known as peripheral devices because they surround
the CPU and make a communication between computer and the outer world.
Input
Devices
Input devices are
necessary to convert our information or data in to a form which can be
understood by the computer. A good input device should provide timely, accurate
and useful data to the main memory of the computer for processing followings
are the most useful input devices.
1. Keyboard: - 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. It contains a total of 101 to 104 keys. A
typical keyboard used in a computer is shown in Fig. 2.6. You have to press
correct combination of keys to input data. The computer can recognize the
electrical signals corresponding to the correct key combination and processing
is done accordingly.
2. Mouse: - Mouse is an
input device shown in Fig. 2.7 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.
3. Scanner:
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).
a. 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.
b. 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.
c. 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.
Output
Devices
1. 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 messages 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.
2. Terminals: It is a very
popular interactive input-output unit. It can be divided into two types: hard
copy terminals and soft copy terminals. A hard copy terminal provides a
printout on paper whereas soft copy terminals provide visual copy on monitor. A
terminal when connected to a CPU sends instructions directly to the computer.
Terminals are also classified as dumb terminals or intelligent terminals
depending upon the work situation.
3. 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.
Input device
In
computing,
an input device is a peripheral
(piece of computer hardware equipment) used to provide data and control
signals to an information
processing system such as a computer
or other information appliance. Examples of input devices include keyboards, mice, scanners,
digital cameras and joysticks.
Many
input devices can be classified according to:
- modality of input (e.g. mechanical
motion, audio, visual, etc.)
- whether the
input is discrete (e.g. key presses) or continuous (e.g. a mouse's
position, though digitized into a discrete quantity, is fast enough to be
considered continuous)
- the number
of degrees of freedom involved (e.g. two-dimensional traditional mice, or
three-dimensional navigators designed for CAD applications)
Output device
An
output device is any piece of computer hardware
equipment used to communicate the results of data processing
carried out by an information processing system
(such as a computer)
which converts the electronically generated information into human-readable
form.[1][2]