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Output is the result of the process. It present data in a form that can be
understood by humans. The most common output devices are discussed below.
Visual display units (VDUs)
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A VDU is found on nearly all computers. The display unit is a television-like
screen called a monitor. It can be used to display lines of text as well as
graphics. The three most important features of a monitor are the size, whether
the monitor is color or monochrome, and the resolution. |
 An
increasing popularity-LCD monitor |
High resolution is very important as it means that more detail can be
displayed. Today's most common visual display is 15'' VGA monitor.
One of the disadvantages of using a monitor is its radiation. With the
improvement in manufacturing technology, the price of LCD has fallen. You can
buy a 15'' viewable LCD with just $4,000. LCD is free of radiation.
Printers
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The display on the VDU is only temporary. If the VDU is switched off, the
display is lost. Often, we want a hard copy or a printed output. The most common
device for generating hard copies is a printer. |
There are two types of printer: Impact printers and non-impact printers
Impact printers
| Dot-matrix printer :
The dot-matrix printer arranges printed dots to form characters
an images. The quality of the output depends on the density of the dots.
Different typefaces are also possible. |
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Dot Matrix
Mechanism
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matrix printers print columns of dots in a serial fashion. The
more dot hammers (pins), the better looking the printed results |
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Line
printer :
Line printer can print one line at a time. A typical line
printer is the drum printer. The drum printer consists of a cylinder with
raised characters on its surface.
Line printers have a fixed character letter style and size. They
are also expensive. However, their big advantage is that they are very
fast. They can print 600 to 2000 lines per minute.
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Line Printer
Today's line printers are
even quieter than laser printers. The
line printer is typically enclosed in a cabinet that completely seals the
unit from the outside world. This used to be essential when line printers
were extremely noisy. Today's line printers are even quieter than laser
printers.
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Daisy
wheel printer :
A daisy wheel printer produces letter quality output for
word processors. It works like a typewriter. The daisy wheel consists of a
circular fan of 'spokes' with alphabetical and numerical characters at the
end of the spokes. Daisy wheel printers cannot produce graphics and only
one character style and size are available. The speed is relatively slow
too. It is not popular now.
Non-impact printers
| Ink-jet printer : |
It uses the dot-matrix principle. Droplets or electrically
charged ink are injected through a nozzle towards the paper. They are
deflected to the proper position when they pass through an electric field.
Printing speed is relatively fast , and the quality is also good. |
| Laser printer : |
A laser printer uses laser beams
and photocopying techniques
for printing. It combines high quality and high speed printing. In the
past, laser printer was very expensive and just common in business uses.
Now the price is becoming much lower. |
Plotters : |
It is capable of producing graphic
output but are usually limited by size and quality. |
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Sound synthesizer
Voice output from computers was developed earlier than speech recognition. It
combines the basic sound units that make up speech. When the computer has to
'say' something, the appropriate codes are processed and a sound is
formed. Sound card is required in producing voice output.
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A pair of voice
speaker |
The usefulness of this output device includes it is used in automatic
telephone answering machines, phone banking system and 'speaking ' dictionary.
It is also of great use to those people who are handicapped by not being able to
speak.
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