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

The shift toward the use of computers instead of controller units in NC systems 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. One of the objectives of CNC and DNC systems is to replace as much of the conventional NC hardware with software as possible, and to simplify the remaining hardware. There are many ways in which functions can be shared between software and hardware in such systems, but all involve some hardware in the controller dedicated to the individual machine.