Q. Explain the graphic display system?

The function of your graphic display system is to display bit-mapped graphics on your monitor.  The image displayed on your system so comprises small dots known as pixels (short for 'picture elements') and your video system includes a description of each of these dots in memory. At any moment display memory comprises exact bit-map representation of your screen image and what is coming after that.  This is as a time-slice of what you see on your monitor. Hence display memory is also known as a Frame buffer. These frames are read dozens of times a second and transmitted in a sequential manner via a cable to monitor.  The monitor receives the train of data and displays it on screen. This occurs by a scanning raster movement from up to down one row at a time.  A CRT (Cathode Ray Tube) based monitor will light its small phosphor dots in accordance with this raster movement.  In this prospect it is like a television that is also a CRT based device.

Figure: Raster Display

The more the number of dots it implies that higher the resolution of the image the sharper the picture is. Richness of the image is also dependant on number of colours (or in other words gray levels for a monochrome display) displayed by system. The higher the number of colours the more is information needed for every dot. Therefore amount of memory (frame buffer) needed by a system is directly dependent on resolution and colour depth needed.