Numerical controller including DNC operation unit

A numerical controller including a direct numerical control (DNC) operation unit, the numerical controller buffering a machining program loaded from an external storage or an external controller via a connection unit in an internal memory and performing automatic operation based on the buffered machining program by an automatic operation execution unit, wherein

• the machining program includes one or a plurality of buffering point instructions that specify a breakpoint for the buffering of the machining program, and
• the automatic operation execution unit includes
• a buffering completion checking result holding unit for checking whether a portion of the machining program to be buffered includes the buffering point instruction and holding a result of the checking in the buffering of the portion of the machining program in the internal memory,
• an execution checking result holding unit for, when the automatic operation execution unit executes a portion of the machining program buffered in the internal memory, checking whether the portion of the machining program to be executed includes the buffering point instruction and holding a result of the checking,
• a comparison unit for comparing the result held by the buffering completion checking result holding unit with the result held by the execution checking result holding unit, and
• an execution unit for performing any one of continuation, suspension, and resumption of the automatic operation based on a result of the comparison,
• wherein, prior to performing the automatic operation based on the buffered machining program, a diagnosis is configured to be made for each of partial areas, which is sandwiched between two of the buffering point instructions, of an entire area of the machining program stored in the external storage or the external controller to determine whether a size of each partial area exceeds a predetermined area size of the internal memory.