Numerical control system, machine tool having numerical control system, and data structure of machining program

A numerical control system comprising:

• a numerical control apparatus that controls driving of a machine tool provided with a tailstock, and
• an external storage device that provides the numerical control apparatus with a machining program, wherein
• the external storage device includes a machining program storage unit that stores a machining program having a data structure including job data corresponding to one product and setup data included in the job data and corresponding to one machining process, the setup data being associated with a plurality of tailstock settings related to the tailstock, and
• the numerical control apparatus includes:
• a tailstock setting buffer including two or more buffer regions each capable of storing one of the tailstock settings;
• an active buffer region selection unit that, when machining using one of the tailstock settings stored in an active buffer region of the respective buffer regions is completed, selects a non-active buffer region as a new active buffer region;
• and
• a tailstock setting writing unit that, when the active buffer region selection unit selects the new active buffer region, writes one of the tailstock settings corresponding to next machining to a non-active buffer region.