Correct Answer - Option 3 : is a method for controlling by means of a set of instructions
Explanation:
Numerical Control
Numerical control (NC) is the name given to the method where the movements of the machine components are controlled by directly inserting the coded instructions, in the form of numbers and letters into the system.
The functional elements of an NC machine tool involve the following
Data Input: The numerical information is read and stored into the tape reader or computer memory.
Data Processing: The programs are read into the machine control unit for processing.
Data Output: The information in the tape is translated into the commands to the servomotors. The servomotors then move table onto which workpiece is there to specific positions by means of stepping motors, lead screws and other devices.
