Transcript Input and Output Part II

Input & Output
Part II
Bayram Güzer
Output
• Output provides the information for the
user.
• Computer systems have several kinds of
outputs.
• Main output units in computer systems are
screens and printers.
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Output
• Example: Suppose that you went to a travel
agency and asked for reservation on an
flight connection. The travel agent will
enter data and make few queries to find
available flights and the results will be
displayed on a screen. If reservation is
made, then the agent can get a printed
output for tickets, traveler's itinerary and the
invoice.
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Computer Screen Technology
• In computer systems, screen is one of the main
elements.
• When you enter data, it appears on the screen.
• The screen is a part of the computer monitor
which also includes electrical components,
monitor stand and etc…
• Soft copy is the screen output because it is
intangible and temporary
• Hard copy is produced by printer on a paper
and it is tangible and permanent
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Common Forms of Monitors
•
•
•
•
Cathode Ray Tube (CRT)
Flat-Panel Screens
Smart Displays
Terminals
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CRT Monitors
• Display text and graphics
– Most are in color
– Some monochrome monitors are used in
applications that have no need for color or
graphics
– Uses of monochrome monitors are in business
applications such as customer inquiry or order
entry systems that no color is needed.
– Graphics card converts signals from the
control unit into the image the user sees
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CRT Monitors
• Most CRT screens uses a technology which is
called as raster scanning.
– Raster scanning is a process of sweeping
(süpürmek) electron beams from back of the
screen.
– The screen display has a phosphorous coating that
glows whenever it is hit by a beam of electrons.
– But the phosphorus doesn’t glow for very long, so
the image must be refreshed often.
– If the screen is not refreshed often enough, the
fading screen image appears to flicker (titreme).
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CRT Monitors
• Scan rate
– The frequency with which the image is refreshed
– The sufficient rate is 80 or 100 times per second
• Interlaced is another method for scanning the
screen.
– In interlaced fashion, first the odd-numbered lines
and then the even-numbered lines are scanned.
– This requires a lower refresh rate without
producing any flickering.
– When animations appear in monitors, interlacing
can create irritating flutter (dalgalanma) effect. For
that reason, most screens are today announced as
non-interlaced which means all lines are scanned in
order.
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CRT Monitors
• A computer screen is divided into dots that is
called as addressable because they can be
addressed individually.
• Each dot can be illuminated individually on the
screen.
• Each dot is potentially a picture element or a pixel.
• Resolution defines clarity (açıklık) of screen
– Measured in pixels (picture elements)
– The more pixels, the higher the resolution
– There are some graphics standards exist
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CRT Monitors
• Dot pitch
– It is the amount of space between dots
– If the dot pitch is smaller, the image is sharp-edged
(keskin kenarlı)
• Most computers come with built-in graphics
compatibility.
– But if the computer doesn’t have built-in graphics, there
will be a need for graphics card or graphics adapter
board.
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Graphic Standards
• Defines the agreement on resolutions, colors,
other issues related to displaying graphics
– Super Video Graphics Adapter (SVGA) is most
common standard
• Provides 800 (horizontal) x 600 (vertical) pixels on the
display
– Other varieties of SVGA exist
– 1024 by 768
– 1280 by 1024
– 1600 by 1200
– Support 16 million colors
• The number of colors that can be displayed depends on
amount of video memory
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Graphic Standards
• Extended Graphics Array (XGA) is a high
resolution graphics standard designed to
replace older standards.
• It provides more simultaneous colors
• It allows monitors to be non-interlaced.
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Flat Screen Monitors
• Liquid crystal display (LCD)
– Originally used for laptops, but making their way to
desktop computers by becoming bigger every day.
•
•
•
•
Very thin (only a few inches)
Produce sharper text images than CRTs
Easier on eyes than CRTs
More expensive than CRTs
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Flat Panel Technologies
• Active-matrix
– Uses many thin-film transistors (TFT)
– Produces brighter image and can be viewed from wider
angles
• Passive-matrix
– Uses fewer transistors
– Cheaper and uses less power
• Gas plasma
– Supports very large displays
– Has brilliant color display
– Viewable at very wide angles
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Smart Displays
• Based on flat-panel
technology
• Each contains its own
processor
• Wireless transmitter-receiver
allows user to control desktop
from anywhere in the house
• Idea was announced by
Microsoft as Mira in 2002,
but the project was cancelled
in December 2003.
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Terminals
• A screen can be part of a terminal attached to a
large computer.
• A terminal consists of an input device, an
output device, and a communications link to
the main computer.
• Smart terminals are the terminals which has
some processing ability of their own CPU.
– Bank tellers use terminals to communicate directly
with a central computer to determine bank balances
and other information.
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Printers
• A printer is a device that produces
information on paper output.
– Old printers were producing only letters and
numbers.
• Most printers have two orientation setting
which is portrait and the landscape.
– Portrait mode prints out on vertical side
– Landscape mode prints out on horizontal side
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Printers
• There are two ways for printing an image
on paper.
– Impact method
• Uses some sort of physical contact with the paper to
produce an image
• Physically strike (hit) to paper, ribbon and print
hammer together
• Line Printers: Impact printers that print entire line at
a time is called as line printers. It is typically used
with mainframe computers for printing lengthy
reports.
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Printers
• There are two ways for printing an image
on paper.
– Impact method
• Dot-matrix printers: Has print head consisting of
one or more columns of pins
• Pins form characters and images as patterns of dots
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Printers
• There are two ways for printing an image on
paper.
– Nonimpact method
• Places an image on a page without physically touching
the page.
• Major nonimpact technologies are laser and ink-jet
printers.
• Laser printers use a light beam to help transfer images to
paper.
• Laser printers produces high-quality output at very fast
speeds.
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Printers
• There are two ways for printing an image
on paper.
– Nonimpact method
• Ink-jet printers spray ink from multiple jet nozzles
• Can print in both black & white and different colors.
• Print quality and speed is not matching that of a
laser printer.
• Less expensive than laser printers but requires high
quality paper so ink doesn’t spread
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Voice Output
• Speech synthesis is the process of enabling machines
to talk to people.
• Voice synthesizers convert data to vocalized sounds
that is understandable to humans.
• Two approaches exist
– Synthesis by analysis - analyzes actual human voice, records
and plays back as needed
– Synthesis by rule - uses linguistic rules to create artificial
speech
• Used in automated telephone-based customer service
applications
– Useful when an inquiry would be followed by a short reply,
such as a balance inquiry, automatic telephone voice survey.
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References
• Capron, H. L. (2000). Computers Tools for an
Information Age.(6th ed.). New Jersey, USA:
Prentice Hall.
• Long, L. & Long, N. (2001). Computers. (8th ed.).
New Jersey, USA: Prentice Hall.
• Smart Display. (n.d.). Retrieved 01 November 2009
from http://www.amazon.com/ViewSonic-airpanelV150-Smart-Display/dp/B00007A5K0
• Smart Displays. (2008). Retrieved 01 November
2009 from http://en.wikipedia.org/wiki/
Smart_Display
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