Rando Scan Systems

An application program is input and stored in the system memory along with a graphics package. Graphics command in the application program are translated by the graphics package into a display file stored in the system memory. This display file is then accessed by the display processor to refresh the screen. This display processor cycles through each command in the display file program once during every refresh cycle. Sometimes the display processor in a random scan system is referred to as a display processing unit or a graphics controller.
Graphics patterns are drawn on a random scan system by directing the electron beam along the component lines of the picture. Lines are defined by the values for their coordinate end points, and these input coordinate values are converted to x and y deflection voltages. A scene is then drawn one line at a time by positioning the beam to fill in the line between specified endpoints.