Output Devices
Output Devices are all part of
the Hardware of a computer
system
Output Devices are about seeing
the results of your work!
Business Studies Stage I Computer Applications
Slide 1
Some Output Devices
Paper
Video Monitor
Sound
Controlling
Other Machines
Business Studies Stage I Computer Applications
Slide 2
Types of Output
• Soft Copy
• Hard Copy
• Communications
Channel
Business Studies Stage I Computer Applications
Slide 3
Screen Output – Soft
Copy
• Video Monitor
– Also called Video Display
Terminal (VDT)
– Image exists in video
memory—VRAM
– Monitor size is measured
diagonally across the
screen
Business Studies Stage I Computer Applications
Slide 4
Pixels
• Images are made up of
dots called pixels for
picture elements
• The number of pixels
determines the clarity of the
picture on the screen
• More pixels = higher resolution
= clearer picture
Business Studies Stage I Computer Applications
Slide 5
Color Depth (Bit Depth)
• This means the amount of information
stored in each pixel about what is being
shown on the monitor
– Monochrome (1 bit of information per pixel)
• This can only be black or white
– Gray-scale (8 bits of information per pixel)
• This can show more shades of grey
– True color (24 or 32 bits of information per
pixel)
• This can realistically reproduce a photograph on
the screen that looks very close to the original
Business Studies Stage I Computer Applications
Slide 6
Examples of Color Depth
The greater the color depth the more colours
that can be represented on the screen
1-bit depth
4-bit depth
8-bit depth
16-bit depth
Business Studies Stage I Computer Applications
Slide 7
Classes of Monitors
CRT (cathode ray tube)
LCD (liquid crystal display)
Business Studies Stage I Computer Applications
Slide 8
CRT (Cathode Ray Tube)
• A CRT is a television-style monitor
• Its features include:
–
–
–
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Clear image
Quick response time
Low cost
Very popular
Business Studies Stage I Computer Applications
Slide 9
Features of CRT Displays
• Display text and graphics
• Monitors differ in resolution
• Standards
– SVGA – 1024 x 768, 1208 x 1024 and 1600 x
1200
– XGA – has same resolutions but supports more
colours
• Screen sizes vary from 15” to 21”
Business Studies Stage I Computer Applications
Slide 10
LCD (Liquid Crystal
Display)
• LCDs comprise flat-panel monitors
• Found on watches, calculators, digital
cameras and notebook computers
–
–
–
–
–
Lighter weight
Crisp,clear images
Extra viewing area for same size
More expensive to buy
Consume less power
Business Studies Stage I Computer Applications
Slide 11
Paper Output – Hard
Copy
• A printer is a device that
produces output on paper
• Most printers today can
produce both text and
graphics
• Two types of printers:
– Impact printers
– Non-impact printers
Business Studies Stage I Computer Applications
Slide 12
Impact Printers
• There is some physical contact with
the paper to produce the image ie
physically striking the paper
• Types
– Line printers
– Dot matrix printers
Business Studies Stage I Computer Applications
Slide 13
Line Printer
• Line printers
– Used by mainframes for
jobs that need a large volume of
printing
– Limited characters available
– Print an entire line at a time
– Cheap to run
– Not high quality
Business Studies Stage I Computer Applications
Slide 14
Dot Matrix Printer
• Have a printhead made up of
columns of pins
– The pins form characters and images
as patterns of dots produced when
the pins strike the paper
– Reasonable quality text and graphics
– Inexpensive to buy and run
– Noisy
Business Studies Stage I Computer Applications
Slide 15
Non-Impact Printers
• Laser Printers
• Ink-jet printers
• Bubble-jet printers
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Slide 16
Laser Printers
• Laser printers
– Image transferred to paper
with a laser beam
• Faster and more expensive
than dot-matrix
• High-resolution output
• Expensive to buy
• Quite expensive to run
Business Studies Stage I Computer Applications
Slide 17
Ink-Jet Printers
• Ink-jet
– Dots of ink are sprayed onto the
paper to form the image
– Reasonably high quality
– Available in colour or B/W
– Speed measured in pages per minute
– Reasonably priced
– Expensive to run
Business Studies Stage I Computer Applications
Slide 18
Plotters
• Used by graphic
designers/architects
– Image transferred to paper with
ink pens
– Very high resolution
– Excellent for scientific and
engineering applications
Business Studies Stage I Computer Applications
Slide 19
Printing Terms
•
•
•
•
•
Dots per inch (dpi)
Pages per minute (ppm)
Characters per second (cps)
Laser printers – 50 ppm
Ink-jet printers – 12 ppm
Business Studies Stage I Computer Applications
Slide 20
Output You Can Hear
• Synthesizers can be
used to generate
music and sounds
• Many computers
have synthesizers
• Sound cards have
built-in synthesizers
Business Studies Stage I Computer Applications
Slide 21
Machines Controlling
Other Machines
• By turning bit information into
movements (robots) or
measurements (sensors), machines
can control other machines:
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Automated factory equipment
Telephone switchboards
Robot arms
Spacecraft
Business Studies Stage I Computer Applications
Slide 22
Output to a Network –
Computer to Computer
• Needs a Communications
channel
• The Internet and WWW
• Needs a modem to
convert data for
transmission across
network
Business Studies Stage I Computer Applications
Slide 23