Numerical Control (NC) is a way to automate machines. In numerical control, the commands these machines get come from a storage medium; they are not controlled and operated manually. The first such machines were Jacquard looms controlled by punched cards. Machine tools for cutting metal were built in the 1940s and 1950s. They used punched tape instructions. Soon, the tools were changed, to use computers. Numerical control with computers is known as Computer Numerical Control, or CNC.