PC Hardware A Beginner’s Guide

(^372) PC Hardware: A Beginner’s Guide
LCD Display Sizes
As illustrated in Table 16-1, LCD flat-panel displays may provide a better bargain on a
price per viewable inch basis. The nominal size of an LCD display is its viewable area as
opposed to the one-inch margin of error used by CRT manufacturers.

Dots and Pixels

The images displayed on a PC’s monitor are created from a pattern of dots in much the same

way as the photographs in a newspaper. Dots are shaded lighter or darker so that your eyes

can form a visual image from them. The CRT creates these dots from the phosphor on the

back of its screen using masking methods that isolate each dot so that it can be illuminated by

an electron gun. (I’ll go into exactly how the dots are created a little later in the chapter.)

A monochrome, or single color, monitor has phosphor of only one color, so that when

the phosphor dots are illuminated, the text and graphic image is a single color on a

contrasting background. Typically, the background is black and the display color is

green, amber, or white.

The image produced on a color monitor is created by illuminated small triangles of

phosphor dots called picture elements, or pixels for short. In the CRT, one-third of the

dots are red dots, one-third are green dots, and one-third are blue dots. These different

colored dots are interspersed evenly on the screen so that a dot of each color can be

grouped with a dot of each of the other colors to form a triangle or pixel.

A color CRT has three electron guns that are used to light up the phosphors in each

pixel. The combinations and intensities used to illuminate the phosphors define the

image produced on the screen. The electron guns sweep over the pixels from side to side,

one row at a time, to create or refresh the displayed image.

LCD displays are of two different types: passive matrix and active matrix. A passive

matrix display has a layer of LCD elements on a grid (matrix) of wires. When current is

applied to the wire intersections, the diodes (pixels) are lighted. A passive matrix refreshes

Nominal Size CRT Viewable Size LCD Viewable Size

14" 13.2" 14"

15" 13.8" 15"

17" 15.9" 17"

19" 18" 19"

21" 19.8" 21"

Table 16-1. Display Nominal versus Viewable Screen Sizes