Page 66 - DCAP101_BASIC_COMPUTER_SKILLS

Unit 4: Secondary Storage Devices

4.2.2.2 LCD Monitor Notes

LCD stands for Liquid Crystal Display, referring to the technology behind these popular flat
panel monitors. An LCD monitor is distinguishable from a traditional CRT monitor as the
latter has a bulky footprint with a depth of several inches and a weight 13-23
kilograms or more, while LCDs are commonly 1-3 inches (2.5-7.5 cm) thick and weigh less
than 4.5 k.
LCD displays were used on laptop computers before the technology improved enough to
make the jump to desktop monitors. An LCD monitor consists of five layers: a backlight, a
sheet of polarized glass, a “mask” of colored pixels, a layer of liquid crystal solution responsive
to a wired grid of x, y coordinates, and a second polarized sheet of glass. By manipulating
the orientations of crystals through precise electrical charges of varying degrees and voltages,
the crystals act like tiny shutters, opening or closing in response to the stimulus, thereby
allowing degrees of light that have passed through specific colored pixels to illuminate the
screen, creating a picture.

Figure 4.15: LCD Monitor

4.2.2.3 Printers
Printers are the most popular output devices used today for producing hard-copy output.
Different types of printers are described below.

Dot-Matrix Printers
Dot-matrix printers arc character printers that print one character at a time. They form
characters and all kinds of images as patterns of dots. Figure 4.16 shows how various types
of characters can be formed as patterns of dots. A Dot matrix printer has a print head that
moves horizontally (left to right and right to left) across the paper. Print contains an array
of pins that can be activated independent of each other to extend and strike against an inked
-n to form patterns of dots on the paper. To print a character, the printer activates the
appropriate set of pins as the print head moves horizontally. For faster printing, many dot-
matrix printers print both ways—while the printer head moves from left to right and while
it moves from right to left, on return. Such method is called bidirectional printing. Figure
4.16 shows a dot-matrix printer.

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