Input Output Devices
Presented by: Manjeet Singh
INPUT AND OUTPUT UNIT
 INPUT UNIT:
 The input unit gets the idea and program from various
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input devices.
The data is provided through input devices such as Key
board, Mouse, track ball and joystick.
Input data can also be provided by scanning images, voice
recording, video recording etc.
OUTPUT UNIT :
The output unit gets the processed data from computer
and sends it to output devices to make them available for
the user of computer.
The output data is provided through output devices like
display screen, printer, plotter and speaker.
 In addition to input and output devices, some devices
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function as both input and output devices. The input
and output devices provide the input to computer as
well as get output from computer.
LIST THE DIFFERENT INPUT AND OUTPUT
DEVICES :
Input devices: key board, mouse, track ball, joystick,
touch screen, light pen, speech recognition system,
digital camera, scanner, MICR, OCR, OMR, barcode
reader.
Output devices : Monitor, visual display terminal,
printer, plotter, computer output on Microfilm(COM),
videos output system, audio response system.
Input output devices : Hard disk drive, floppy disk
drive, USB drive, CD drive, DVD drive.
INPUT DEVICES
 Input devices allow user and other applications to
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input data into the computer, for processing. The data
input to a computer can be in the form of text, audio,
video, etc. Input devices are classified as follows :Human data entry devices :Keyboard
Pointing devices – mouse, track ball, joystick
Pick devices – light pen, touch screen.
Source data entry devices :Audio input- speech recognition
Video input- digital camera
Scanner- hand held scanner, flat bed scanner
Optical scanner- OCR, OMR, MICR, barcode reader.
Human Data Entry Devices
 Input device that require data to be entered manually to
the computer are identified as human data entry devices.
The data may be entered by typing or keying in, or by
pointing a device to a particular location.
(1) KEYBOARD :-
Features :-
Keyboard is a common input device. It is
used for entering the text data for inputting the data user
types the data using the keyboard. When the data is
being typed, the display monitor displays the typed data.
Cursor is a vertical line, an underscore, blinking line etc.
 Working :-
When a key is pressed, keyboard interacts with a
keyboard controller
and keyboard buffer. The keyboard
controller scores the code of pressed key in keyboard buffer and
informs the computer software that an action has happened on
the keyboard.
 POINTING
DEVICES :-
These devices are used for
providing the input to computer by moving the device to point to
a location on computer monitor. Operations like move, click and
drag can be performed using the pointing devices. Mouse, track
ball, joystick and digitizing tablet are some of the common
pointing devices.
 MOUSE
 Features:- it is the most common pointing input device. The
mouse may also be used to position the cursor on screen, move
an object by dragging, or select an object by clicking. It provides
an easy way to select and choose commands from menus, dialog
boxes, icons etc.
 Description :- Mouse is a small hand-held device having 2
or 3 buttons on its upper side. Mouse also has a small wheel
button. A mouse is classified as physical mouse and optical
mouse.
 Working :- In a physical mouse, rollers and sensors are used
to sense the direction and rate of movement of mouse. When an
optical mouse is moved, a beam of light is reflected from its
underside.
 TRACK BALL : Features:- Track ball is a device that is a variant of the mouse
but has the functionality of mouse. It is easy to use and takes less
space than a mouse. Track ball is generally built in laptops since
there is no space for the mouse to move on the lap.
 Working :- Track ball works in the same way as a physical
mouse
JOYSTICK
 Features : Joystick is a device which is commonly used for
playing video games. Joystick is mainly used to control the speed
of cursor and is thus popular in games involving speed like
racing and flying games.
 DIGITIZING TABLET :
 Features : It is an input device used primarily to input drawings,
sketches etc. It is used for Computer Aided Design (CAD) for
the design of buildings, maps etc.
 Description : It consist of two parts-electronic tablet and pen.
The electronic tablet is a flat bed tablet. The pen looks like a ball
pen but has an electronic head.
PICK DEVICES
 Pick devices are used for providing input to the
computer by pointing to a location on the computer
monitor. Light pen and Touch screen are some
common pick devices.
 Light pen :
 Features : It is a light sensitive pen-like input device
and is used to select objects directly on the screen. It is
used for making drawing, graphics and for menu
selection.
 TOUCH SCREEN:
 Features : It is an input device used in applications like
Automated Teller Machine (A T M),public information
computer like Hospitals, airline reservations etc.
 Description : It consist of a clear glass panel that is
placed over the view area of computer screen.
 Working : Touch screen have an infrared beam that
criss cross the surface of screen. Some touch screen
have ultrasonic waves that cross the surface of screen.
Source Data Entry Devices
 AUDIO INPUT DEVICE : It can be provided to the
computer using human speech. It can be used for
making telephone calls, to record voice etc.
 VIDEO INPUT DEVICES : It is provided to the
computer using Video Cameras and Digital Camera.
Video camera capture full motion video images.
Digital camera works like video camera but can
capture still images.
 OPTICAL INPUT DEVICE :It allow computers to use
light as a source of input. Common optical input
devices are MICR,OMR,OCR and Bar Code Reader.
SCANNER
TYPES OF SCANNER :
 Hand Held Scanner : They are portable and are placed
over the document to be scanned. They have to be
moved at a constant speed over the document to be
scanned.
 Flat Bed Scanners : They provided high quality scan in
a single pass. It is a box shaped machine similar to a
photocopy machine and has a glass top and a lid that
covers the glass.
OPTICAL CHARACTER RECOGNITION (OCR)
 An optical character recognition is a technique
for the scanning of a printed page, translating
it, and then using the OCR software to
recognise the image as ASCII text that is
editable.OCR is used to read character of
special type font printed on conventional paper
with conventional ink.
MAGNETIC INK CHARACTER READER (MICR)
 MICR reads these characters by examining their
shapes, using a 7* 10 matrix, it determines, from the
response of the segments of the matrix to the
magnetic head. It is mostly used in bands.
 OPTICAL MARK READER (OMR):
 In this method, special preprinted forms are designed
with boxes which can be marked with a dark pencil or
ink. Such a document is read by a document reader
called optical mark reader which transcribes the marks
into electrical pulses which are transmitted to the
computer.
BARCODE READER
 They are adjacent vertical lines of different width that
are machine readable. They are fast and accurate. They
enable faster service to the customer and are also used
to determine the items being sold, no. of each item or
to retrieve the price of item.
Output Devices
 Output devices provide output to the user, which is
generated after processing the input data. Output
devices are classified as follows:
 HARD COPY DEVICES: The output obtained in a
tangible form on a paper or any surface is called hard
copy output. Printer, Plotter and microphone are
common hard copy output devices.
Printer
 A Printer prints the output information from the computer
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onto a paper. Printers can be divided into distinct
categories:
(A) IMPACT PRINTER:
*Line Printers : A printer prints a complete line at a time.
Printing speed vary from 150 lines to 2500 lines per minute
with 90 to 100 characters on 15 inch line. There are two
types of line printers :
(a) Drum printer : it consists of cylindrical drum on which
characters are embossed. A printer can print up to 132
characters per line.
(b) Chain printer : it consists of steel band on which the
characters are embossed.
 *Character printers : they print one character at a time,
with the print head moving across a line. These
printers normally print 30 to 300 characters per second
(CPS).
 (a) Dot Matrix printers : it is the most popular serial
printer. In the DMPs , the capital letters are formed by
using 5* 7 matrix of dots that is 5- dot rows and 7 – dot
columns.
 (B) NON-IMPACT PRINTERS:
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These are faster and quierer than impact printers.
they produce high quality output and can be used for
printing text and graphics in black and white color.
 *InkJet printers : Some printers direct a high velocity
stream of ink towards the paper. In some systems the ink
stream is broken into droplets by an ultrasonic transducer.
 *Laser printers : these printers make use of office copier
technologies. The speed can be up to 10- 15 pages per
minute.
COMPUTER OUTPUT ON MICROFILM
A microfilm is in fiche or roll format and is used to
record computer output directly from the computer
tape or cartridge. COM is a high speed low cost
process. The standard roll film is 16 mm wide with a
film image that is 1/24 of the original document. COM
is used for storing output in banking and insurance
applications , medical X-rays etc.