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Unformatted text preview: er certain lighting
conditions. This is because unlike the phosphors used in CRT monitors, the liquid
crystals do not glow when charged, so there is not enough contrast between the images
and their background to make them clearly legible under all lighting conditions. To take
care of this problem, some LCD monitors put a light source behind the screen. Although
this makes the screen easier to read, the light source requires additional power, which can
be a problem for portable computer systems that often run on battery.
Printers are the most commonly used Output devices today for producing hard-copy
output. There are many ways to classify a wide variety of printers available today. The
most commonly used ways are:
Printing technology used. According to this classification, the common types of
printers are dot-matrix printers, ink-jet printers, drum printers, chain/band printers and
Approach of printing. According to this classification, printers are classified as
impact printers and non-impact printers. Impact printers use the approach of hammering
a typeface against paper and inked ribbon to produce printed output. Nonimpact printers
do not hit or impact a ribbon to print. They use thermal, electrostatic, chemical or inkjet
technology to produce printed output. Impact printers can produce multiple copies by
using carbon in a single print cycle, which is not possible with a non-impact printer.
However, an impact printer is noisy in operation and normally uses covers to reduce the
noise level. Non-impact printers are quiet in operation.
3. Speed of printing. According to this classification, printers are classified as character
printers, line printers and page printers. As the names imply, a character printer prints one
character at a time, a line printer prints one line at a time, and a page printer prints an
entire page at a time. Accordingly, printer speeds are measured in characters-per-second (cps) for character printers, lines-per-min...
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- Spring '14