1 - Graphics Displays

Abstract

This chapter discusses how graphics video displays work in a theoretical way. The first computer monitors or cathode-ray tubes (CRTs), or video display tubes (VDTs) were only capable of displaying a single color. They are called monochrome monitors. The chapter explains the methods of programming a monitor, namely, raster scan and vector scan. With a vector scan monitor, commands are given to steer the electron beam to draw the desired pattern. This method gives very clear, crisp looking lines; however, it can flicker and be quite slow if a complex pattern is drawn. With the raster scan technique, all pixels are covered each time the screen is refreshed. There are two types of color mixing techniques, additive, and subtractive. The chapter explains these color mixing techniques, and how color monitors work. The Hercules monitor is a high quality monochrome graphics monitor made by the Hercules company for IBM PC clones. It is the simplest of the PC graphics monitors as in many ways; it is very much like the monochrome monitor. The CGA monitor was IBM's first PC color graphics monitor. With CGA monitors, there is only one page for any graphics mode; however, other monitors have modes that support more pages. The chapter discusses the features of enhanced graphics adapter (EGA) monitors, multi-color graphics array (MCGA) monitors, video graphics array (VGA) monitors, and super VGA (SVGA) monitors.