In random-scan systems, an application program is inputted and stored in the system memory alongside a graphics package. Graphics commands within the program are translated by the graphics package into a display file, which is then stored in the system memory. The display processor accesses this display file to refresh the screen. During each refresh cycle, the display processor cycles through each command in the display file program.
The display processor in a random-scan system is sometimes referred to as a display processing unit or a graphics controller.
To draw graphic patterns on a random-scan system, the electron beam is directed along the component lines of the picture. Lines are defined by specifying the coordinates of their endpoints. These input coordinate values are then converted into x and y deflection voltages. The scene is drawn one line at a time, with the beam positioned to fill in the line between the specified endpoints.
By understanding the architecture and components of raster-scan systems and random-scan systems, we gain insight into the inner workings of interactive graphics systems, which play a significant role in various applications such as computer-aided design, gaming, and multimedia.