A computer numerical control, or CNC, operator is a person who loads and unloads parts from a CNC machine, starts the machine cycle and performs tests to ensure that machined parts conform to specifications. They are not usually qualified machinists and do not make changes to the CNC machine.
A CNC operator works closely with a CNC machinist. It is the operator's job to check that parts are being machined properly. Tools and other parts of CNC machines need to be periodically replaced and will occasionally break while in use. A proficient CNC operator can save a great deal of waste by spotting non-conformity issues quickly and notifying a CNC machinist who can make necessary modifications or perform necessary maintenance.