Video 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, as it is also called. From its beginning, when it could display only text to today'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 application program, such as Microsoft Word, Adobe PhotoShop, or Paint Shop Pro. Regardless 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 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 to form text or 2D images or tiny polygons and triangles for 3D graphics.
The text, images, shapes, and shadows formed by the pixels and triangles are generated in two phases: the transform and lighting phase and the setup phase.
