APPARATUS FOR RAPIDLY CLEARING THE OUTPUT DISPLAY OF A COMPUTER SYSTEM

A computer output system having a first full screen bitmapped memory, a second full screen bitmapped memory, logic circuitry for providing input signals for writing information to be displayed by an output device to each position of the first memory, logic circuitry for storing in the second memory the positions of each position of the first memory to be written to the output device, and logic circuitry for comparing the signal stored at each position of the first memory and the signal stored at the same position of the second memory to determine whether information at the position is to be written to the output device.