Abstract: A system for use with large libraries of existing technical drawings for permitting the drawings to be electronically captured and digitally stored in a central data base. As needed, the documents can be retrieved, displayed, electronically revised, and printed out. The system includes scanners which scan existing drawings to generate a bit stream of pixel data which is then compressed and stored in a mass storage unit. A drawing revisory subsystem is provided capable of operating in a DRAWING REVISION MODE and a DRAWING REDISPLAY MODE. When operating in the DRAWING REVISION MODE, as the operator inputs revisory commands, the revisory subsystem generates primitives which modify the displayed drawing in real time by changing a bit map stored in a dedicated pixel memory driving a display monitor. Additionally, however, the revisory subsystem automatically caches the primitives defining the desired drawing revisions.