Chapter 09 io devices 2o-p

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Computer Fundamentals: Pradeep K. Sinha & Priti SinhaComputer Fundamentals: Pradeep K. Sinha & Priti Sinha
Slide 1/58Chapter 9: Input-Output DevicesRef Page
In this chapter you will learn about:
§ Input/Output (I/O) devices
§ Commonly used input devices
§ Commonly used output devices
§ Other concepts related to I/O devices
Learning ObjectivesLearning Objectives
148

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I/O DevicesI/O Devices
§ Provide means of communication between a computer
and outer world
§ Also known as peripheral devices because they
surround the CPU and memory of a computer system
§ Input devices are used to enter data from the outside
world into primary storage
§ Output devices supply results of processing from
primary storage to users
148
Role of I/O DevicesRole of I/O Devices
Input
data
from
external
world
Results of
processing
in human
acceptable
form
Input data coded
in internal form
Processed data
in internal form
CPU
and
Memory
Input
Devices
Output
Devices
148

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Commonly Used Input DevicesCommonly Used Input Devices
§ Keyboard devices
§ Point-and-draw devices
§ Data scanning devices
§ Digitizer
§ Electronic cards based devices
§ Speech recognition devices
§ Vision based devices
149
Keyboard DevicesKeyboard Devices
§ Allow data entry into a computer system by pressing a
set of keys (labeled buttons) neatly mounted on a
keyboard connected to a computer system
§ 101-keys QWERTY keyboard is most popular
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The Layout of Keys on a
QWERTY Keyboard
The Layout of Keys on a
QWERTY Keyboard
Esc F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12
~
`
!
1
@
2
# 3 $
4
%
5
^
6
&
7
*
8
(
9
)
0
_
-
+
= ← Backspace
Q W E R T Y U I O P {
[
}
]Tab
←
→
A S D F G H J K L
:
; “
‘
← EnterCaps Lock
Z X C V B N M <
,
>
.
?
/Shift Shift
Alt
|

Ctrl Alt
?
/
Ctrl
Print Screen Scroll Screen Pause
Insert Home
Page Up
Delete End
Page Down
← ↓ →
↑
Num Lock Caps Lock Scroll Lock
Num Lock
/ * -
7
Home
8
↑
9
Pg Up
4
← 5
6
→
1
End
2
↓
3
Pg Dn
0
Ins
.
Del
+
Enter
149
Point-and-Draw DevicesPoint-and-Draw Devices
§ Used to rapidly point to and select a graphic icon or
menu item from multiple options displayed on the
Graphical User Interface (GUI) of a screen
§ Used to create graphic elements on the screen such as
lines, curves, and freehand shapes
§ Some commonly used point-and-draw devices are
mouse, track ball, joy stick, light pen, and touch screen
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MouseMouse
Commonly used in personal computers and workstations
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TrackballTrackball
Commonly used in laptop (notebook) computers
Ball to be
rolled with
fingers
Click buttons
151

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JoystickJoystick
Commonly used for video games, flight simulators,
training simulators, and for controlling industrial robots
Stick
Socket
Ball
Click button
Light
indicator
152
Electronic PenElectronic Pen
§ Pen-based point-and-draw device
§ Used to directly point with it on the screen to select
menu items or icons or directly draw graphics on the
screen
§ Can write with it on a special pad for direct input of
written information to a system
§ Pressure on tip of a side button is used to cause same
action as right-button-click of a mouse
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Touch ScreenTouch Screen
§ Most simple, intuitive, and easiest to learn of all input
devices
§ Enables users to choose from available options by simply
touching with their finger the desired icon or menu item
displayed on the screen
§ Most preferred human-computer interface used in
information kiosks (unattended interactive information
systems such as automatic teller machine or ATM)
152
Data Scanning DevicesData Scanning Devices
§ Input devices that enable direct data entry into a computer
system from source documents
§ Eliminate the need to key in text data into the computer
§ Due to reduced human effort in data entry, they improve
data accuracy and also increase the timeliness of the
information processed
§ Demand high quality of input documents
§ Some data scanning devices are also capable of recognizing
marks or characters
§ Form design and ink specification usually becomes more
critical for accuracy
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Image ScannerImage Scanner
§ Input device that translates paper documents into an
electronic format for storage in a computer
§ Electronic format of a scanned image is its bit map
representation
§ Stored image can be altered or manipulated with an
image-processing software
153
A flat-bed scanner A hand-held scanner
Two Common Types of Image ScannersTwo Common Types of Image Scanners
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Optical Character
Recognition (OCR) Device
Optical Character
Recognition (OCR) Device
§ Scanner equipped with a character recognition software
(called OCR software) that converts the bit map images
of characters to equivalent ASCII codes
§ Enables word processing of input text and also requires
less storage for storing the document as text rather than
an image
§ OCR software is extremely complex because it is difficult
to make a computer recognize an unlimited number of
typefaces and fonts
§ Two standard OCR fonts are OCR-A (American standard)
and OCR-B (European standard)
154
Optical Mark Reader (OMR)Optical Mark Reader (OMR)
§ Scanner capable of recognizing a pre-specified type of
mark by pencil or pen
§ Very useful for grading tests with objective type
questions, or for any input data that is of a choice or
selection nature
§ Technique used for recognition of marks involves focusing
a light on the page being scanned and detecting the
reflected light pattern from the marks
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A sample use of OMR for grading tests with objective type questions
For each question, four options are given out of which only one is
correct. Choose the correct option and mark your choice against
the corresponding question number in the given answer sheet by
darkening the corresponding circle with a lead pencil.
1. The binary equivalent of decimal 4 is:
a) 101
b) 111
c) 001
d) 100
2. The full form of CPU is:
a) Cursor Positioning Unit
b) Central Power Unit
c) Central Processing Unit
d) None of the above
3. Which is the largest unit of storage among the following:
a) Terabyte
b) Kilobyte
c) Megabyte
d) Gigabyte
(a) Question sheet
(b) Pre-printed answer sheet
1.
a b c d
2.
a b c d
3.
a b c d
Indicates direction in which the
sheet should be fed to the OMR
Sample Use of OMRSample Use of OMR
155
Bar-code ReaderBar-code Reader
§ Scanner used for reading (decoding) bar-coded
data
§ Bar codes represent alphanumeric data by a
combination of adjacent vertical lines (bars) by
varying their width and the spacing between them
§ Scanner uses laser-beam to stroke across pattern
of bar code. Different patterns of bars reflect the
beam in different ways sensed by a light-sensitive
detector
§ Universal Product Code (UPC) is the most widely
known bar coding system
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21000 67520
Product category character
0 – grocery products
3 – drugs and health related
products, etc.
Manufacturer/supplier
identification number Specific product code
number
0
An Example of UPC Bar CodeAn Example of UPC Bar Code
156
Magnetic-Ink Character Recognition (MICR)Magnetic-Ink Character Recognition (MICR)
§ MICR is used by banking industry for faster processing
of large volume of cheques
§ Bank’s identification code (name, branch, etc.), account
number and cheque number are pre-printed (encoded)
using characters from a special character set on all
cheques
§ Special ink is used that contains magnetizable particles
of iron oxide
§ MICR reader-sorter reads data on cheques and sorts
them for distribution to other banks or for further
processing
156

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§ It consists of numerals 0 to 9 and four special characters
§ MICR is not adopted by other industries because it supports only
14 symbols
MICR Character Set (E13B Font)MICR Character Set (E13B Font)
157
DigitizerDigitizer
§ Input device used for converting (digitizing) pictures,
maps and drawings into digital form for storage in
computers
§ Commonly used in the area of Computer Aided
Design (CAD) by architects and engineers to design
cars, buildings medical devices, robots, mechanical
parts, etc.
§ Used in the area of Geographical Information System
(GIS) for digitizing maps available in paper form
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Stylus in the form
of cross-hair cursor
Table top
Digitizing tablet
A DigitizerA Digitizer
158
Electronic-card ReaderElectronic-card Reader
§ Electronic cards are small plastic cards having encoded
data appropriate for the application for which they are
used
§ Electronic-card reader (normally connected to a
computer) is used to read data encoded on an
electronic card and transfer it to the computer for
further processing
§ Used together as a means of direct data entry into a
computer system
§ Used by banks for use in automatic teller machines
(ATMs) and by organizations for controlling access of
employees to physically secured areas
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Speech Recognition DevicesSpeech Recognition Devices
§ Input device that allows a person to input data to a
computer system by speaking to it
§ Today’s speech recognition systems are limited to
accepting few words within a relatively small
domain and can be used to enter only limited kinds
and quantities of data
158
Types of Speech Recognition SystemsTypes of Speech Recognition Systems
§ Single word recognition systems can recognize only a
single spoken words, such as YES, NO, MOVE, STOP, at
a time. Speaker-independent systems are mostly of
this type
§ Continuous speech recognition systems can recognize
spoken sentences, such as MOVE TO THE NEXT
BLOCK. Such systems are normally speaker-
dependent
(Continued from previous slide..)
158

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§ For inputting data to a computer system by a person in
situations where his/her hands are busy, or his/her eyes
must be fixed on a measuring instrument or some other
object
§ For data input by dictation of long text or passage for
later editing and review
§ For authentication of a user by a computer system based
on voice input
§ For limited use of computers by individuals with physical
disabilities
Uses of Speech Recognition SystemsUses of Speech Recognition Systems
159
Vision-Input SystemsVision-Input Systems
§ Allow computer to accept input just by seeing an object.
§ Input data is normally an object’s shape and features in
the form of an image
§ Mainly used today in factories for designing industrial
robots that are used for quality-control and assembly
processes
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Commonly Used Output DevicesCommonly Used Output Devices
§ Monitors
§ Printers
§ Plotters
§ Screen image projector
§ Voice response systems
160
Types of OutputTypes of Output
§ Soft-copy output
§ Not produced on a paper or some material that can be touched
and carried for being shown to others
§ Temporary in nature and vanish after use
§ Examples are output displayed on a terminal screen or spoken out
by a voice response system
§ Hard-copy output
§ Produced on a paper or some material that can be touched and
carried for being shown to others
§ Permanent in nature and can be kept in paper files or can be
looked at a later time when the person is not using the computer
§ Examples are output produced by printers or plotters on paper
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MonitorsMonitors
§ Monitors are the most popular output devices used for
producing soft-copy output
§ Display the output on a television like screen
§ Monitor associated with a keyboard is called a video
display terminal (VDT). It is the most popular I/O
device
160
Monitor
Keyboard
A video display terminal consists of a monitor and a keyboard
MonitorsMonitors
160

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§ Cathode-ray-tube (CRT) monitors look like a television
and are normally used with non-portable computer
systems
§ Flat-panel monitors are thinner and lighter and are
commonly used with portable computer systems like
notebook computers. Now they are also used with non-
portable desktop computer systems because they
occupy less table space.
Types of MonitorsTypes of Monitors
160
PrintersPrinters
Most common output devices for producing hard-copy
output
160

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Dot-Matrix PrintersDot-Matrix Printers
§ Character printers that form characters and all kinds of
images as a pattern of dots
§ Print many special characters, different sizes of print and
graphics such as charts and graphs
§ Impact printers can be used for generating multiple copies
by using carbon paper or its equivalent
§ Slow, with speeds usually ranging between 30 to 600
characters per second
§ Cheap in both initial cost and cost of operation
161
ABCDEFGHIJKLMNO
PQRSTUVWXYZ
0123456789-.,
&/$*#%@=(+)
Formation of Characters as a pattern of dotsFormation of Characters as a pattern of dots
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A Dot Matrix PrinterA Dot Matrix Printer
161
Inkjet PrintersInkjet Printers
§ Character printers that form characters and all kinds of
images by spraying small drops of ink on to the paper
§ Print head contains up to 64 tiny nozzles that can be
selectively heated up in a few micro seconds by an
integrated circuit register
§ To print a character, the printer selectively heats the
appropriate set of nozzles as the print head moves
horizontally
§ Can print many special characters, different sizes of print,
and graphics such as charts and graphs
(Continued on next slide)
161

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§ Non-impact printers. Hence, they cannot produce
multiple copies of a document in a single printing
§ Can be both monochrome and color
§ Slower than dot-matrix printers with speeds usually
ranging between 40 to 300 characters per second
§ More expensive than a dot-matrix printer
Inkjet PrintersInkjet Printers
162
An Inkjet PrintersAn Inkjet Printers
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Drum PrintersDrum Printers
§ Line printers that print one line at a time
§ Have a solid cylindrical drum with characters embossed
on its surface in the form of circular bands
§ Set of hammers mounted in front of the drum in such a
manner that an inked ribbon and paper can be placed
between the hammers and the drum
§ Can only print a pre-defined set of characters in a pre-
defined style that is embossed on the drum
§ Impact printers and usually monochrome
§ Typical speeds are in the range of 300 to 2000 lines per
minute
162
Printing Mechanism of a Drum PrinterPrinting Mechanism of a Drum Printer
Hammers (one for each band)
Paper
Solid
cylindrical
drum with
embossed
characters
Ribbon
N N N N N N N N N N N N N N
W W W W W W W W W W W W W W
R R R R R R R R R R R R R R
V V V V V V V V V V V V V V
U U U U U U U U U U U U U U
T T T T T T T T T T T T T T
S S S S S S S S S S S S S S
Q Q Q Q Q Q Q Q Q Q Q Q Q Q
P P P P P P P P P P P P P P
O O O O O O O O O O O O O O
Total number of bands is equal to the maximum
number of characters (print positions) on a line
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Chain/Band PrintersChain/Band Printers
§ Line printers that print one line at a time
§ Consist of a metallic chain/band on which all
characters of the character set supported by the
printer are embossed
§ Also have a set of hammers mounted in front of
the chain/band in such a manner that an inked
ribbon and paper can be placed between the
hammers and the chain/band
163
§ Can only print pre-defined sets of characters that
are embossed on the chain/band used with the
printer
§ Cannot print any shape of characters, different
sizes of print, and graphics such as charts and
graphs
§ Are impact printers and can be used for generating
multiple copies by using carbon paper or its
equivalent
§ Are usually monochrome
§ Typical speeds are in the range of 400 to 3000
lines per minute
Chain/Band PrintersChain/Band Printers
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Laser PrintersLaser Printers
§ Page printers that print one page at a time
§ Consist of a laser beam source, a multi-sided mirror, a
photoconductive drum and toner (tiny particles of oppositely
charged ink)
§ To print a page, the laser beam is focused on the electro
statically charged drum by the spinning multi-sided mirror
§ Toner sticks to the drum in the places the laser beam has
charged the drum’s surface.
§ Toner is then permanently fused on the paper with heat and
pressure to generate the printer output
§ Laser printers produce very high quality output having
resolutions in the range of 600 to 1200 dpi
164
§ Can print many special characters, different sizes of
print, and graphics such as charts and graphs
§ Are non-impact printers
§ Most laser printers are monochrome, but color laser
printers are also available
§ Low speed laser printers can print 4 to 12 pages per
minute. Very high-speed laser printers can print 500
to 1000 pages per minute
§ More expensive than other printers
Laser PrintersLaser Printers
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A Laser PrintersA Laser Printers
164
PlottersPlotters
§ Plotters are an ideal output device for architects,
engineers, city planners, and others who need to
routinely generate high-precision, hard-copy graphic
output of widely varying sizes
§ Two commonly used types of plotters are:
– Drum plotter, in which the paper on which the
design has to be made is placed over a drum that
can rotate in both clockwise and anti-clockwise
directions
– Flatbed plotter, in which the paper on which the
design has to be made is spread and fixed over a
rectangular flatbed table
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Paper
Design drawn
on the paper
A Drum PlotterA Drum Plotter
166
Design
drawn on
the paper
Paper
A Flatbed PlotterA Flatbed Plotter
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Screen Image ProjectorScreen Image Projector
§ An output device that can be directly plugged to a
computer system for projecting information from a
computer on to a large screen
§ Useful for making presentations to a group of people
with direct use of a computer
§ Full-fledged multimedia presentation with audio,
video, image, and animation can be prepared and
made using this facility
166
Voice Response SystemsVoice Response Systems
§ Voice response system enables a computer to talk to
a user
§ Has an audio-response device that produces audio
output
§ Such systems are of two types:
§ Voice reproduction systems
§ Speech synthesizers
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Voice Reproduction SystemsVoice Reproduction Systems
§ Produce audio output by selecting an appropriate
audio output from a set of pre-recorded audio
responses
§ Applications include audio help for guiding how
to operate a system, automatic answering
machines, video games, etc.
167
Speech SynthesizersSpeech Synthesizers
§ Converts text information into spoken sentences
§ Used for applications such as:
§ Reading out text information to blind persons
§ Allowing those persons who cannot speak to
communicate effectively
§ Translating an entered text into spoken words in
a selected language
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Key Words/PhrasesKey Words/Phrases
§ Bard code reader
§ Cathode Ray Tube (CRT)
§ Chain/Band printer
§ Data scanning device
§ Digitizer
§ Digitizing tablet
§ Dot-Matrix printer
§ Drum plotter
§ Drum printer
§ Electronic card reader
§ Electronic Pen
§ Flatbed plotter
§ Flatbed Scanner
§ Graphical User Interface
§ Hand-held scanner
§ Hard-copy output
§ Image Scanner
§ Information Kiosk
§ Inkjet printer
§ Input/Output device
§ Joystick
§ Keyboard device
§ Laser printer
§ Magnetic-Ink Character Recognition (MICR)
§ Monitor
§ Mouse
§ Optical Character Recognition (OCR)
§ Optical Mark Reader (OMR)
§ Peripheral device
§ Phonemes
§ Plotter
§ Point-and-draw device
§ Printer
§ QWERTY keyboard
§ Screen Image Projector
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§ Soft-copy output
§ Speech synthesizer
§ Stylus
§ Touch Screen
§ Trackball
§ Universal Product Code (UPC)
§ Video Display Terminal (VDT)
§ Vision-input system
§ Voice recognition device
§ Voice reproduction system
§ Voice response system
Key Words/PhrasesKey Words/Phrases
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