Computer Numerical Control: A CAM technology using computers to control cutting machines such as milling machines and lathes to cut specified three-dimensional shapes. CNC has been used since the early 1970s. Prior to this, prepared tapes controlled machines and the process was called simply Numerical Control (NC).
Found on http://www.encyclo.co.uk/local/20846
(CONTROL SYSTEMS GLOSSARY) Computer Numerical Control allows machines to be operated from PLCs by means of a numerical code. Found on https://www.encyclo.co.uk/local/20479