Numerical controller

A numerical controller comprising:

• a display configured to display a machining path graphic screen;
• and
• a processor configured to:
• analyze a machining program prior to machining to generate a syntax tree of the machine program;
• draw an unmachined machining path on the machining path graphic screen, on a basis of a result of an analysis of the machining program prior to the machining;
• store, prior to the machining, information on a block serving as a restart position candidate where the machining is to be restarted after the machining is interrupted, the restart block candidate being extracted from the syntax tree generated by the analysis of the machining program prior to machining;
• display current positions under machining moment by moment during the machining;
• draw, when the machining is interrupted, a machining position corresponding to a head of the block serving as a stored restart position candidate, on the machining path displayed on the machining path graphic screen;
• receive, from a user, designation of a machining positon at which the machining is to be restarted, from among machining positions corresponding to restart position candidates drawn on the machining path displayed on the machining path graphic screen;
• set a block corresponding to the machining position designated by the user as a restart block;
• and
• receive, from the user, an instruction to restart the machining, and restart the machining at the machining position designated by the user in response to receiving the instruction to restart the machining.