Lucid 3-D, created by PCSG, Inc. and sold by DacEasy, Inc., is a
spreadsheet program for MS-DOS. The feature that sets it apart from
others is that it is memory-resident, so you can bring it up on top
of other DOS programs and exchange data with them. Unlike simple
TSRs, however, Ludid 3D is a full featured spreadsheet. It features
linking, macros, windowing, intelligent recalculation, background
recalculation, and user-definable functions.