A very flexible gate array that speeds the job of designing, updating, or varying the logic circuitry that turns standard microprocessor and memory ICs into computers and peripheral equipment is examined. The gates on this kind of IC are interconnected under software control, and downloaded into local memory cells from a program written by the user, which can alter it almost at will. The array is manufactured with a grid of interconnections consisting of metal segments and programmable switching points. The user's program defines which switching points are on and which are off, and in this way groups and interconnects the gates into useful functions. On conventional gate-array ICs, the interconnections are made once and for all by the manufacturer using photolithographic masks. Various types of arrays and methods for programming them are described. The approach to designing them is discussed, highlighting differences from the process for factory-configured gate arrays. Some example applications are presented. >