Computers: Computer-based machine-tool control: The best place to inject a computer in numerical control is locally, not as a controller of many systems

An important advance in the philosophy of numerical control (NC) of machine tools took place during the early 1970s. That advance was the shift toward the use of computers instead of controller units in NC systems, and it produced both computer numerical control (CNC), in which a self-contained NC system for a single machine tool includes a dedicated computer processor controlled by stored instructions to perform some or all of the basic numerical control functions; and direct numerical control (DNC), which refers to a system of several machine tools directly controlled by a central computer.