video graphics - how does a video card work?

video graphics elektor september 1983 • • • how does a video card work? While researching the background for the VDU (Video Display Unit) card published elsewhere in this issue it occurred to us that it might not be a bad idea to look at how all those characters appear on the screen. In other words, how is the image of the characters built up and what does a video card do exactly? That is what we will try to clarify in this article and even if you have no intension of building a VDU card, it is still an interesting subject. • • •••■•• • • - • • • • SIMMI■ • • .• • • •• which we will return later. In television the video signal is modulated onto a carrier wave, so that a receiver and decoder section are also needed to regain the pure video signal from the received signal. The principles of how a television builds up an image on its screen have been dealt with in detail before in Elektor (September 1977, p. 9-33) so there is not real...