Computer Input and Output Devices

An input device is any hardware component that
allows you to enter data and instructions onto a
computer. Most Widely used input devices are
1. Keyboard
2. Mouse
3. Microphone
4. Scanner
5. Digital camera
6. Stylus
7. Joysticks
8. Light Pen

The most commonly used input device is the
keyboard on which data is entered by manually
keying in or typing certain keys. A keyboard
typically has 101 or 105 keys.

The keyboard allows the computer user to enter
words, numbers, punctuation, symbols, and special
function commands into the computer’s memory.

Is a pointing device which is used to control the
movement of a mouse pointer on the screen to
make selections from the screen. A mouse has one
to five buttons. The bottom of the mouse is flat and
contains a mechanism that detects movement of
the mouse.

Variants of the Mouse - Trackpads
• A trackpad is a touch-sensitive pad that provides the
same functionality as a mouse.
• To use a trackpad, you glide your finger across its
surface.
• Trackpads provide a set of buttons that function like
mouse buttons.

Variants of the Mouse - Trackballs
• A trackball is like a mouse turned upside-down.
• Use your thumb to move the exposed ball and your
fingers to press the buttons.
Many styles of
trackball are
available.

Scanner is a light sensitive device that helps you
copy or capture images, photos, and artwork
that exist on paper.

Digital camera
A digital camera can store many more pictures
than an ordinary camera. Pictures taken using
a digital camera are stored inside its memory
and can be transferred to a computer by
connecting the camera to it. A digital camera
takes pictures by converting the light passing
through the lens at the front into a digital
image.

Microphone is a input device
used to input audio to
Computer.
• Three main types of
microphones are:
Desktop microphones
Headsets
Directional microphones

Stylus is an input device consisting of a thin
stick that uses pressure to enter information
or to click and point
• Styluses are used with:
PDAs
Tablet PCs
Graphics tablets

The main use of a joystick is to
play computer games by
controlling the way that
something moves on the
screen.

Light pen
•A light pen is a small ‘pen-shaped’ wand,
which contains light sensors.
•It is used to choose objects or commands on
the screen either by pressing it against the
surface of the screen or by pressing a small
switch on its side.
•A signal is sent to the computer, which then
works out the light pen’s exact location on the
screen.
•The advantage of a light pen is that it doesn’t
need a special screen or screen coating.

An output device is any hardware component
that conveys information to one or more
people. Three commonly used output devices
are
1.Printer
2. Monitor
3. Speakers

Monitors, commonly called as Visual Display Unit
(VDU), are the main output device of a
computer. It forms images from tiny dots,
called pixels that are arranged in a rectangular
form. The sharpness of the image depends
upon the number of pixels.
There are two kinds of viewing screen used for
monitors.
 Cathode-Ray Tube (CRT)
 Flat- Panel Display

 A CRT monitor contains millions of tiny red, green,
and blue phosphor dots that glow when struck by an
electron beam. Electron beam travels across the screen
to create a visible image.
 In a CRT monitor tube, the cathode is a heated
filament.
 The heated filament is in a vacuum created inside a
glass tube. The electrons are negative and the screen
gives a positive charge so the screen glows.

 The flat-panel display refers to a class of video devices
that have reduced volume, weight and power
requirement in comparison to the CRT. You can hang
them on walls or wear them on your wrists. Current
uses of flat-panel displays include calculators, video
games, monitors, laptop computer, graphics display.
 The flat-panel display is divided into two categories:
 Emissive Displays - The emissive displays are devices
that convert electrical energy into light. Example are
plasma panel and LED(Light-Emitting Diodes).
 Non-Emissive Displays - The Non-emissive displays
use optical effects to convert sunlight or light from
some other source into graphics patterns. Example is
LCD(Liquid-Crystal Device)

A speaker is a device that
produces computer output
as sound. Speakers are
common devices in
computer systems
Examples include:
• Built-in speaker
• Two-device set speakers
• Surround sound speakers

A printer produces a paper
copy of information
generated by a
computer.
There are two types of
printers:
 Impact Printers
 Non-Impact Printers

The impact printers print the characters by striking
them on the ribbon which is then pressed on the
paper.
Characteristics of Impact Printers are the following:
 Very low consumable costs
 Very noisy
 Useful for bulk printing due to low cost
 There is physical contact with the paper to produce
an image
These printers are of two types
 Character printers
 Line printers

Non-impact printers print the characters without
using ribbon. These printers print a complete page
at a time so they are also called as Page Printers.
These printers are of two types
 Laser Printers
 Inkjet Printers
Characteristics of Non-impact Printers
 Faster than impact printers.
 They are not noisy.
 High quality.
 Support many fonts and different character size.

Computer Input and Output Devices

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