Computer system Input and Output Devices

1. Introduction to Computer System
Input Devices & Output Devices
C. P. Divate

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. Input / Output ( I / O)Devices

4. 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

5. 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.

6. 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.

7. 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.
Types of Mouse:
a) Mechanical, b) Optical, c) Cord-Less,

8. Input Devices
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.

9. 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.

10. Input Devices
Speech Recognition Device: Mike
• 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.

11. Input Device
Digital Camera / Web 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.

12. 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.

13. 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 andplotter
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.

14. 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.

15. Output Devices
Monitors: 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
Monitors:

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
Projector:

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.
Types of Printer
• Laser Printers.
• Inkjet Printers.
• Dot Matrix Printers.
• 3D Printers.

20. Output Devices
Printer:
Types of Printer
• Laser Printers.
• Inkjet Printers.
• Dot Matrix Printers.
• 3D Printers.

21. Output Devices
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.

22. 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.
Types Of Speakers:
• Built-in Computer Speakers
• Headphones
• Stand-alone Computer Speakers
• 2.0 or Two Computer Speakers
• 2.1 Computer Speakers
• 5.1 Computer Speakers
• 7.1 Computer Speakers
• Wireless Computer Speakers
• Bluetooth Speakers
• Wi-Fi Speakers