Computer:
Computer is
an electric device, which is used in almost all fields of life. Computer
receives instruction or data through input devices. It works on these
instructions in processor and provides meaningful results through output
devices. A computer can be divided into three main units.
Input units:
Such parts
of computer through which a computer can receive data are called input units.
E.g.: keyboard, mouse, microphone etc.
OR
The device from that a computer receives instructions is known
as input device. Data in any form is first digitized, i.e. converted into
binary form by the input devices before being fed to the CPU. This unit is also
called the “receiving section” of a computer system.
Keyboard:
It is one
of the most useful input devices. It provides convenient to feed data in a
computer. A computer keyboard is similar to an electronic typewriter keyboard
with little modification. It has some additional keys like function keys, arrow
keys, numeric keys etc.
Mouse:
Mouse is a
pointing device which is use to select an option and have two buttons to click
on any option. Now a days laser type mouse is used.
Scanner:
It scans
the image of the information exposed to it and conveys these to computer’s
memory for further processing.
Light pen:
The light
pen looks like an ordinary pen, but its tip is light sensitive detector. It is
use to write/indicate information directly on monitors screen. When tip of the
pen touched the surface of screen, the computer locates its position in the
form of x-y coordinates of that point. A wire to CPU connects this pen. The
written information is, at the same time conveyed to memory also. For example,
you might have seen a circle drawn around a fielder during cricket match
telecast. This circle is drawn by the light pen.
Magnetic
tape and cartridges are used to input data into computer for various
applications.
Output devices:
Such part
of a computer where by a computer provides us the results of processing are
called output units. The output units receive the data from CPU in the form of
binary bits. Some common output deices are listed below.
Monitor:
The results
are termed as output from computer, output is displayed on a device that is
similar to TV and is called monitor known as VDU (visual display unit). The
data can be presented on the screen either as words, numbers, graphics, tables
or diagrams. Monitor use the technology of cathode ray tube (CRT). Usually it
is of 14” screen size when measured diagonally and has a 25*80 (25 rows and 80
character per row) display. Display of output on monitor is power dependent,
vanishes when power is switched off. Many different types of monitor are in
common use. These may be of VGA, SVGA, MVGA and EVGA types, depending on the resolution.
They are.
Paper white monitor:
A display
monitor in which text and graphics character are displayed in black against the
white background to resemble the appearance of printed page. Some manufacturers
Monochrome monitor
Color monitor
E.g. monitor,
printer, plotter etc.
Processing unit:
This is the
main part of a computer therefore it is also called the brain of computer
system. It is contained on a single integrated circuit or “chip”. All jobs of
processing are carried out in this unit that is also called (C.P.U) central
processing unit.
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