Numerical Control (NC) is a way to automate machine tools. 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 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 Computerized numerical control, or CNC.
Nowadays, it is possible to make a program that can run on such machine tools, based on a CAD drawing of the piece to be produced.
The first attempts to automate machines were done in the 19th century, using so called cams. These are basically wheels that change the position of notches, and can control a machine with this. The basic difference to modern NC is that these cams only automated one given task; modern NC and CNC machines can be programmed to a greater extent.