Numerical control (NC) refers to the automation of machine tools that are operated by abstractly programmed commands encoded on a storage system, as opposed to controlled manually as with handwheels or levers. Such NC machines started being build in the 1940's as they were modified with motors that moved the controls to follow destination points fed with punched tape. It wouldn't be long before these mechanisms were augmented with analog and digital computers, creating the modern day computer numerical control (CNC) machine tools, which have revolutionized the machining process.
In modern CNC systems, end to end component design is highly automated using CAD and computer aided CAM programs. The programs produce a computer file that is interpreted to extract the commands needed to operate a particular machine, and then loaded into the CNC machine for production machining.
Since different tools are needed to effect the over-all design of the component like drills, saws mill bits, taps, end mills, etc... modern machines often combine multiple tools into a single cell. In other cases, a number of different machines are used with an external controller with human or robotic operators that move the components from machine to machine. In either case the complexity of steps needed to produce any part is highly automated and ultimately produces a part, which closely matches the original CAD design created.