Introduction, Keyboard, Pointing Devices, Speech Recognition, Digital Camera, Scanners, Optical Scanners. Introduction, Classification of Output, Hard Copy Output Devices, Printers, Plotters, Computer Output Microfilm (COM), Soft Copy Output Devices, Monitors, Audio Output, Projectors, Terminals.

1. Introduction to Computer System
Input Devices & Output Devices
Prepared By
S.K. Barnwal
Assistant Professor
Arka Jain University
Research Scholar (NIT, Jamshedpur)

2. Objectives
After studying this unit you should be able to understand:
the basic concepts of input/output devices;
functions of input/output devices;
types of input/output devices;
types of monitors, printers, scanners and graphics tablet
 newer technologies in computer hardware.

3. Inputs are data or signals received by the computer system. An Input
unit takes the input and converts it into binary form, so that it can be
easily understand by the system.
If computer is not communicating with the external world then it will
be of no use. Thus, a computer must have a system to receive
information from the outside world and must be able to communicate
results to the external world. For this, a computer consists of
input/output devices. Input and output devices can also be written as
I/O devices.
I/O devices of a computer system are the devices that connect users to
computer. Input devices let us to transfer data and user command into
the computer system. Input devices are used to interact with the
computer system. For example, we can type in data by using a
keyboard, we can give command/ instruction using voice recognition
system, or we can input data in picture form by using a scanner in
computer system etc.

4. On the other hand, output devices display the result of input data or
signals after processing of our given input instructions or command.
Examples of these could be our computer’s monitor, which displays all
the programs which are running on the computer, as well as the printer,
which will print out a hard copy of the information which is saved in
our system.
Input and output devices allow the computer system to interact with the
outside world by moving data into and out of the computer system.

5. I/O Devices
Examples of some input devices
are:
• Keyboard
• Mouse
• Joystick
• Microphone
• Bar code reader
• Graphics tablet
• Pen drive
• CD/DVD
• Digital Camera
Examples of some output devices
are:
• Monitor
• Printer
• Plotter
• Speaker

6. Input Devices
Keyboard:
It is the most common i/p device used for entering data and information
into the computational system. This is the standard input device
attached to all computers. The keyboard is a primary device for
inputting text by pressing a set of keys. All the keys are neatly mounted
in a keyboard connected to the computer system.
Standard keyboard used with most computer system, have enough keys
to make them useful for any type of application. The layout of
keyboard is just like the traditional typewriter of the type QWERT,
contains a total of 101 to 104 keys some extra command keys and
function keys.
In general, a computer keyboard has following keys :
1. Alphanumeric Keys: It includes letters and numbers.
2. Punctuation Keys: These include comma, period, semicolon etc.
3. Special Keys: These can be function keys, control keys, arrow keys and
Caps lock keys etc.

7. Input Devices
Keyboards generally utilize integrated circuits to perform essential
functions, such as determining the combination of 1s and 0s, or binary
code, to send to the CPU, corresponding to each key pressed by the
user so that system can understand. The wireless function is achieved
by infrared signals or by radio frequency.
In general all the modern keyboards of computer are classified as:
(a) Original PC keyboard having 84 keys;
(b) Advance Technology (AT) Keyboard having 101-104 keys;
(c) Multimedia Keyboard having 120 – 140 keys.

8. Input Devices
Pointing Devices:
1. Mouse: It is a pointing device which is used to input data and
information into the computer system by pointing on it. It is a
handy device which can be moved on a smooth surface to cause the
movement of a cursor on the screen. Physically, it contains a small
case, held under one of the user’s hands with one or more buttons.
For GUI-based systems a mouse is an essential pointing-device.
The cursor of the mouse moves in the same direction in which the
mouse ball rolls.
Its name is derived from its shape that looks like a mouse, with its
connecting wire that one can imagine to be the mouse’s tail. A Mouse
rolls on a small ball and has two or three buttons on the top. When you
roll the mouse across a flat surface on the screen, sensors sense the
mouse in the direction of mouse movement. The cursor moves very fast
with a mouse giving you more freedom to work in any direction. It is
easier and faster to move through a mouse compared to movement
using keys.

9. Input Devices
Types of Mouse:
a) Mechanical, b) Optical, c) Cord-Less,
2. Trackball: It is also a pointing device having a movable ball
mounted on a stationary device, can be rotated manually by using
fingers. In a trackball, the ball is placed on the top along with buttons
which can be rolled with the fingers. These are used in playing video
games.
Mouse and mobile phones
are equipped with trackballs
to navigate addresses as well
as play games.

10. Input Devices
3. Joystick: It is a pointing device used as a remote control device for a
computer playing video games to indicate the position. It has a stick
that pivots on a base and is used for controlling the action in video
games. The User moves a spherical ball with the help of a stick in the
joystick as opposed to the trackball where fingers are used for moving
the ball. Joysticks are also used for controlling machines such as
cranes, trucks, underwater unmanned vehicles, flight simulators,
industrial robots etc.

11. Input Devices
Speech Recognition Device:
Speech recognition devices were introduced in the early 1970s. Mostly,
such systems contain a database of stored voice patterns. This database
of voice patterns is generally stored in a recognition unit or in
secondary storage. A microphone, attached to the keyboard or
recognition unit, records the spoken word patterns. A built-in
microprocessor then compares, word by word, these patterns with the
stored patterns and transmits the results of the comparisons to a
computer for processing. A sentence must be spoken as a series of
disjoined words and numbers spoken as a series of digits and not as a
single number. Speech recognition devices are generally used in
situations where access to a switch or control is not possible or where a
user's hands are otherwise occupied.

12. Input Device
Digital Camera:
It is an electronic device takes still photographs, video or both, digitally
by recording images via an electronic image sensor. Digital cameras
can do things which film cameras can’t, for example displaying images
on screen immediately after they are recorded. It looks like ordinary
cameras but have sufficient memory in the form of chips to store
thousands of images, rather than using photographic films. Images
recorded on a digital camera can be cropped for editing, deleted and
various types of special effects can be created by using Photoshop
software.

13. Input Devices
Scanners:
It is an input device used to feed data in the form of pictures into the
computer system. Optical scanners scan images, printed text,
handwriting, or an object, and converts it to a digital image. Examples
of scanners are a desktop or flatbed scanner. In scanners the document
is placed on a glass window for scanning. Mechanically driven
scanners that move the document are typically used for large-formatted
volume of documents. One more type of scanner is a planetary scanner.
This scanner takes photographs of books and documents. Three
dimensional scanners are used for producing three-dimensional models
of objects.

14. Output Devices
There are three types of output devices based on the type of output
produced by the computer in the following form:
1. soft copy: The output on the screen is called a soft copy. Ex; Visual Display
Unit (CRT, LCD, TFT, LED) Screen, Flat Monitor, Projector etc.
2. hard copy: Hard copies are tangible computer outputs. Ex; printer and plotter
3. sound output: The device which gives a sound output. Ex; Speaker
Monitors:
One of the most important output devices in computer system is its
screen commonly called monitor. It is an output device and displays all
the programs and applications which are running on the computer
system. A Monitor is the visual display unit of the computer system. It
displays images generated from the video output. It displays images
without keeping a permanent record.

15. Output Devices
Monitors:
A Graphic display is made up of a series of dots called ‘pixels’ (picture
elements) whose pattern produces images in computer system. Each
dot on the screen is defined as a separate unit which can be addressed
separately. Since each dot on the screen can be controlled separately it
gives greater flexibility in drawing pictures. The Number of dots per
inch (dpi) is called the resolution of the screen and represents the
quality of the computer system.
There are various kind of monitors are available.
 Monitors are on the basis of technology
CRT (Cathode Ray Tube) Monitor
LCD (Liquid Crystal Display) Monitor
TFT LCD (Thin Film Transistor Liquid Crystal Display)
LED (Light Emitting Diode)

16. Output Devices
 Monitors are on the basis of signal
Analog Monitor
Digital Monitor
 Monitors are on the basis of size
14 inch
17 inch
32 inch
40 inch
 Monitors are on the basis of resolution
1024 by 768 pixels
1280 by 1024 pixels
1600 by 1200 pixels

17. Output Devices
Projector:
This is a type of video projector used for displaying videos, images, or
computer data on a large screen or any other flat surface. Several
people in a classroom can view the output on a wide screen at the same
time. It is a modern equivalent of the slide projector or overhead
projector. A beam of high-intensity light travels through thousands of
shifting pixels in a LCD display. This beam of light then passes through
a lens which projects and focuses the image on the surface. . It receives
video signals and projects the corresponding image on a projection
screen. It uses a lens system for this projection.

18. Output Devices
Computer Output Microfilm (COM):
It is a process for copying data from storage media on a computer onto
microfilm. COM can be produced as microfiche or as 16mm-roll
microfilm or we can say that it is a technology enabling the output of
computers be recorded directly on microfilm rather than on paper. It is
a blending of the computer, microphotography, and electronics. This
process is faster than printing on paper, and the information produced
is more accessible and occupies less space than paper reports.
A COM system usually consists of a recorder/developer and a reader.
The recorder/developer equipment may be in a single unit or each unit
may be separate. The recorder reads computer magnetic tape, reduces
the physical size of the data, and transforms it onto film, which is then
developed. The reader, the main vehicle for retrieving information on
microfilm, magnifies the reduced data on the film so a report user can
read it.

19. Output Devices
Printer:
Printers are used for producing output on paper. There are a large
variety of printers and printing devices which can be classified
according to the print quality and printing speed.
Plotters:
A Plotter is a device that draws pictures on a page as output, after
receiving a print command from the computer. It is also called a graph
plotter. In plotters pens are used to draw lines on the paper, which is
placed in the plotter.

20. Output Devices
Speakers:
Computer speakers, or multimedia speakers, are external speakers,
commonly equipped with a low-power internal amplifier which
produces sound as output. External speakers are connected with a
computer by using a plug and socket.
Microphone:
It is an acoustic-to-electric transducer or sensor used to convert sound
signals into electrical signals. This input device was originally invented
by Emile Berliner in 1877, and allows you to record voices or sounds
and place them onto computers, generally as a wave file.

21. Output Devices
Terminals:
A computer terminal is an electronic or electromechanical hardware
device that can be used for entering data into, and transcribing data
from, a computer or a computing system. Ex; Teletype
Early terminals were inexpensive devices but very slow compared to
punched cards or paper tape for input, but as the technology improved
and video displays were introduced, terminals pushed these older forms
of interaction from the industry. A related development was
timesharing systems, which evolved in parallel and made up for any
inefficiencies of the user's typing ability with the ability to support
multiple users on the same machine, each at their own
terminal/terminals.