Input and Output
Chapter 4
The User Connection
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1
Functions of Computer
Systems
Recall that there are four main
functions of computer systems.
Secondary
Storage
Input
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Processing
Output
2
Input and Output
The computer user
is very aware of
inputting data and
the output
(processed
information) that
is the result.
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Inputting Data
•
•
•
•
Keyboard
Mouse
Trackball
Magnetic-ink
character
recognition
• Scanner
• Optical mark
recognition
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• Optical character
recognition
• Bar codes
• Handwritten
characters
• Voice input
• Touch screens
• Looking
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Keyboard
A keyboard is similar to a typewriter
keyboard. Not all keyboards are
traditional. Customized keyboards
can be found in business, schools,
and homes.
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Mouse
The mouse movement corresponds to
movement of the pointer (cursor) on
the screen.
A mouse also has
one or more buttons
which allow selection
of items on a screen.
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Trackball
The trackball stays in one
place while the user
rolls the ball directly
with one hand.
Trackballs are ideal when
a flat surface does not
exist.
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Magnetic-ink Recognition
The most common
example of
characters made
of magnetic
particles can be
seen on personal
checks.
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Scanner
A scanner is an optical recognition system
that uses light to scan an image and convert
it into electrical signals.
The signals are then processed so that the
image appears on the computer monitor.
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Optical Mark Recognition
This technique uses a
machine to sense
marks on a piece of
paper.
Computer-graded answer
sheets rely on optical
mark recognition
(OMR) to score tests.
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Exam
a b c d
1.
OOOO
2.
3.
4.
5.
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
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Optical Character
Recognition (OCR)
OCR devices use a
light source to read
special characters
or printed text.
OCR devices can
“read” pages in a
book or sale tags on
store merchandise.
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Bar Codes
Bar codes appear on the product as a
series of zebra-like stripes.
Bar codes are used to identify a
product when read by a device called
a bar code reader.
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Handwritten Characters
Machines can read
handwritten
characters.
However, the size,
completeness, and
legibility of the
handwriting must
follow rigid rules.
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machines
that can
read
13
Voice Input
Speaking to a computer
requires speech
recognition devices.
The computer processes
the sounds into
binary code and can
“learn” what the code
means.
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Hello
Hal.
Hello
Hal.
14
Touch Screens
Touch screens
are designed so
that if touched,
the computer
knows what
the person has
selected.
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Yes
N
o
15
Looking
In the future, input
might be gathered
from our eye
movements, and
watching images
that appear on
our retina.
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16
Output of Information
Useful information for the user can
take on a variety of forms:
• Computer screens
• Printers
• Voice output
• Music and sound
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Computer Screens
Screen output is
known as soft copy
because it is
intangible and
temporary.
Most computer
screens are of the
cathode ray variety.
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Cathode Ray Tube (CRT)
Most CRT screens use raster scanning
to produce the image.
The image must be refreshed often. The
rate of refreshing is called scan rate.
The image we see actually consists of
dots (pixels) on the screen that are
either illuminated or not.
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Pixels
Resolution is determined
by the number of pixels
on the screen.
The amount of space
between pixels is dot
pitch, which
determines image
quality.
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Resolution Just Gets
Better
There are two
common
resolutions
available today:
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SVGA •800x600
•1024x768
•1280x1024
•1600x1200
XGAmore colors
21
Flat Screens
Some computer
screens use liquid
crystal technology.
LCDs are popular
with laptop
computers.
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Terminals
Terminals integrate a monitor,
keyboard and communications
link.
Smart terminals have their own
CPU
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Printers
A printer is an output device that
produces a hard copy of your work
(a printout on paper).
There are two ways to
print onto paper:
• Impact
• Non-impact
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Impact Printers
An impact printer makes physical
contact with the paper to produce an
image.
Impact printers are practical for print
jobs in which quantity matters or
when multiple (carbon) copies are
needed simultaneously.
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Non-Impact Printers
Non-impact printers put the image on
the page without physically striking
the paper.
These printers are best when quality
is important.
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Voice Output
Hello
Dave.
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Synthesizing speech is
much easier for a
computer than speech
recognition.
There are two methods:
• Synthesis by analysis
• Synthesis by rule
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Synthesis by Analysis
In this method of speech synthesis,
the output device analyzes the
input of a human voice speaking
words.
The words are stored and the sounds
are processed.
Later, the computer “talks” by
reproducing the words as needed.
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Synthesis by Rule
In this method of speech synthesis,
the output device applies a complex
set of linguistic rules to create
artificial speech.
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Music and Sound Output
• May be as simple
as attaching
speakers to the
computer.
• For more serious
output, add sound
chips to simulate
different
instruments or
sound effects.
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• Use MIDI to record
and playback musical
compositions
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Computer Graphics Output
Examples of this kind of output
include:
•
•
•
•
Business graphics
Video graphics
CAD/CAM
Education
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• Computer art
• Science
• Sports
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Business Graphics
Business graphics is a
powerful way to turn
numerical data into
more meaningful
information.
April Sales by Teams
(A, B, C, and D)
The addition of color increases understanding.
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Video Graphics
Video graphics
combines
computer
graphics and
sound, with the
ability to
animate a series
of frames.
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TV’s Special Effects
Many television
programs and
movies rely on
the special
effects made
possible with
video graphics
technology.
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CAD/CAM
Computer-aided
design (CAM) and
computer-aided
manufacturing
use computers to
design, build, and
test products.
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Digital Cameras
• Digital cameras take photographs and
store them internally
• Photos are then sent to the computer for
output, or stored on disk.
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Ethics and Data
Just because a computer will allow
you to input data and produce new
information as output, doesn’t
always mean it is legal or right to
do so.
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Ethics and Data
Is the situation described below
ethical?
Use computer software to
substitute one person for another
in a photograph.
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Ethics and Data
Is the situation described below
ethical?
Erase contents of e-mails that may
help someone filing suit against your
company.
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Conclusion
Newer input and output devices are
announced regularly.
Users reap the benefits of
improvements in performance and
ease of use.
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