About The Video System of Your PC
About The Video System of Your PC
About The Video System of Your PC
Introduction
All computers are connected to some type of display. That
is called a monitor . Monitors are available in many
different types and sizes (generally 12 to 21 inches
diagonal screen size). The monitor is a part of the
computer video system. To understand how to obtain a good
screen image, we need to look at the complete video system.
It includes three elements:
Fast development
The video system has developed as explosively as the rest
of the PC during the last 10 years. These improvements have
occurred in different areas:
• The monitors – both the tubes and the electronics
continue to improve. They render better and better
images - sharper, with better resolution and better
colors.
• New monitor types are arriving on the market. The flat
TFT screens are in the stores. In few years, they will
replace CRT all over the world.
• The video cards are getting faster. They can deliver
better images, which the new monitors are capable of
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The video system is a sub system in the PC, with its own
technological development. At the same time, monitors and
video cards are areas, where manufacturers and dealers
often cut corners. As an ordinary user, you can improve
your screen images significantly with careful planning.
That holds true when you buy your PC - you must select your
video system carefully. It also holds true for existing
video systems, where better drivers and software optimizing
can help produce the optimal screen image.
Common principles
The principles in these screen types are quite different,
but the screen image design rests on the same concepts:
• Video RAM: All video cards have some RAM. How much
depends on the desired color depth. Video cards
usually have 1, 2 or 4 MB RAM for normal usage.
Greater resolutions
The greater the number of pixels in the screen image, the
better the resolution. And the greater the resolution, the
sharper the image appears. The lowest resolution seen in
modern PC's is found in text based DOS screen images, which
are 640 x 480 pixels. That is called a VGA image. VGA was
the standard, until Windows came on the market. Back in the
eighties, there were even lower standards, like CGA, which
I will not even describe. As the PC's got more powerful,
around 1990 a demand developed for better screen
resolutions. Windows is a graphic environment, and it works
fine in all screen resolutions. The same programs work as
well in 640 x 480 as in higher resolutions. Many DOS games
also demanded better screen quality. Anyway, VGA was the
last "real standard" working on any PC. Screen resolution
was since improved relative to VGA, and the term SVGA
(Super VGA) came into use. Later came XGA and other names,
which each described different resolutions.
Actually, the terms SVGA and XGA are not used much anymore.
Instead we are looking at resolution, image frequency and
color depth. But, let us stay with the resolution. It ties
in with screen size, the bigger the screen the bigger the
possible resolution.
Screen size
Monitor screen sizes are measured in inches, just like TV
sets. The most common sizes are 14", 15", 17", 19" and 21"
screens. The measurement is the diagonal size of the screen
However, the nominal size of the common CRT screens does
not give a true description of the visible size. The
nominal size is the internal diagonal of the the picture
tube. However, the visible diagonal is smaller! The visible
diagonal of a CRT screen is always about 10% smaller.
Therefore, the visible image on a 17"
CRT screen and a 15.5" LCD screen is about the same.
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Colors
Colors are a must! Good PC’s must be able to display many
colors on the screen.
16 or 24 bit colors
We must be able to vary the three basic colors in a number
of steps. Typically. we use 8 bits for each color. 8 bits
provide 256 possible variations – from 0, giving a light
intensity of zero – and up to step 255, giving maximum
intensity of that color. That will provide the following
possible color variations:
Screen savers
Early monitors had low quality phosphor coatings. That
could result in a screen image to "burn-in" if left
unattended. You could clearly see that in work places,
where the PC was used for only one program. That program
image remained clearly on the screen, after the PC was shut
down. That led to screen savers. This prevents the regular
image from burning in. Screens have improved a lot since
then - the screen image will not "burn in" in a modern
screen. At the same time, screen savers have developed into
an art form of their own. Use the screen savers. They can
spice up day-to-day work.