Hewlett-packard Company

David C Hempstead

Richard H Jundanian

This invention provides a method and apparatus for controlling the type of information displayed at each display pixel on the video monitor of a video display system. A number of video RAMs are provided which number is at least equal to the number of different types of information. A bitmap is stored for each type of information in the video RAMs in interspersed fashion, a selected number of bits for select display pixels of the bitmap for a given type of information being simultaneously stored in said RAMs, followed for each RAM by the selected number of bits for the same selected display pixels for the bitmap of at least one other information type. No more than one bitmap bit for a given display pixel is stored in any video RAM. The addressing of the RAMs for read out of the bitmap is shifted so that bits for the same display pixels for all of the bitmaps are simultaneously read out from the RAMs. The bits of the bitmaps for each display pixel are then prioritized, the prioritizing including determining and generating an indication of the type of information which has priorty and is to be displayed at each display pixel.

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Methuen, MA, United States of America

David C Hempstead