PC Hardware A Beginner’s Guide

(^386) PC Hardware: A Beginner’s Guide
Aperture grill monitors use stripe pitch instead of dot pitch to indicate the distances
between two stripes of the same color. Common stripe pitch distances are about the same
as current dot pitch distances—from .24 mm to .32 mm. However, the two measurements
cannot be compared to each other. Stripe pitch distances compare only to other stripe
pitches. Like a dot pitch though, smaller is definitely better.

Scan Rates

How fast a CRT is able to complete its sweep left to right and complete the refresh of the

entire screen of pixels is an indicator of its brightness and image sharpness. The quicker

the screen can refresh, the less likely it is that parts of the display will fade before they can

be refreshed again.

Two scan rates used to indicate the frequencies in hertz of the CRT. The first is the

horizontal scan rate that indicates in kilohertz (KHz) or the number (in increments of one

hundred) of left to right sweeps that can be made by the electron gun to refresh the pixels

on a single row. The second is the vertical scan rate, which indicates how fast the electron

gun can complete a scan of the entire display area. Table 16-6 lists the scan rates for the

more commonly used CRT resolutions. Remember that it takes one hundred kilohertz to

make one hertz.

Raster versus Vector Graphics

An image drawn on the screen of a CRT can be produced using two different drawing

techniques: raster or vector. Essentially, all paint and imaging software uses raster graphics,

and virtually all freehand drawing and animation software uses vector graphics. Nearly

all graphic output devices, including monitors and printers, are raster devices. In fact,

vector graphics must be translated before they can be printed. Most printers include a

special processor, called a raster image processor, to perform this conversion. On the PC,

metafile formats, such as the Windows Metafile format (.wmf files), combine the best of

bitmapped (raster) and vector graphics into a single file.

Resolution Horizontal Scan Rate Vertical Scan Rate

640 × 480 31.5 to 43KHz 60 to 85Hz

800 × 600 32 to 54KHz 50 to 85Hz

1024 × 768 48 to 80KHz 60 to 100Hz

1280 × 1024 52 to 80KHz 50 to 75Hz

Table 16-6. Typical CRT Scan Rates