V
ideo output is a very important part of the PC, at least to the user. Without video
displays, the output from the PC would be much slower and most likely limited to
text only. The outputs on the PC are geared to the human senses of sight and
sound. Think about doing any task on a PC without the use of the monitor; it would be
virtually impossible. The PC’s video system and monitor share the credit for the growth
in popularity of the PC. It is doubtful that the PC would be nearly as popular if its output
were printed on paper.
The heart of the PC’s video system is the video card, or graphics card or graphics
accelerator,asitisalsocalled.Fromitsbeginning,whenitcoulddisplayonlytexttotoday’s
3D and full motion video, the video card has essentially performed the same tasks. This
chapter provides a look into the video card and how it generates the video display and
the technology it uses to do it.
The video card does a lot more than just provide a connection for the monitor to the
PC. It also controls the look, movement, color, brightness, and clarity of images displayed
on the monitor. The video card processes every bit of the data sent to the monitor by any
of the software running on the PC, turning digital data into text, graphics, and images on
the monitor.How a Video Card Works
The text and images displayed on the monitor are generated by software running on the
PC. The software could be the operating system, as in the case of Windows, or in an appli-
cation program, such as Microsoft Word, Adobe PhotoShop, or Paint Shop Pro. Regard-
less of its type, the software generates graphic data and instructions for a series of video
frames that instruct the PC’s CPU exactly how each frame of video output should look.
The CPU and the video card then work together (more on this later) to create the image
displayed on the monitor.
The instructions generated by the operating system or application software is sent to
the CPU. The CPU sorts through the data and extracts the instructions it needs and sends
the rest on to the video card. Depending on the type and capabilities of the video card, the
CPU, the video card, or both create images by formatting pixels (picture elements—see
Chapter 16) to form text or 2D images or tiny polygons and triangles for 3D graphics.
Thetext,images,shapes,andshadowsformedbythepixelsandtrianglesaregenerated
in two phases: the transform and lighting phase and the setup phase.Transform and Lighting Phase
The images displayed on the monitor rarely remain the same. As you type a letter or play
a card game, each keystroke or mouse click causes a change in the display. Each of these
changes, regardless of how bold or subtle they may be, are called transforms. In the trans-
form phase, the graphic data is analyzed to determine just what has changed and the
image data is constructed to change the displayed image accordingly.(^254) PC Hardware: A Beginner’s Guide