Numerical controller

A numerical controller for controlling a machine tool for machining a work on the basis of an NC program for execution including a variable, comprising:

• an NC program for variable-check storage region for storing an NC program for variable-check indicating an execution situation of the NC program for execution;
• NC program reading unit for sequentially reading the NC program for execution on a predetermined unit basis;
• NC program analyzing unit for analyzing the predetermined unit of the program read by the NC program reading unit;
• workpiece machining unit for controlling the machine tool on the basis of a result of analysis by the NC program analyzing unit;
• and
• a variable value table sequentially holding a variable value assigned to the variable at time of execution of the predetermined unit of the program read by the NC program reading unit, wherein
• the NC program analyzing unit has variable replacing unit, character string for variable-check creating unit, and NC program for variable-check writing unit;
• the variable replacing unit outputs, to the workpiece machining unit, a program in which the variable included in the predetermined unit of the program read by the NC program reading unit is replaced with a variable value obtained from the variable value table on the basis of the variable value and also outputs, to the character string for variable-check creating unit, the predetermined unit of the program read by the NC program reading unit and the variable value obtained from the variable value table;
• the character string for variable-check creating unit replaces a character string included in an instruction affected by the variable in the predetermined unit of the program with a character string for variable-check on the basis of the predetermined unit of the program read by the NC program reading unit and the variable value obtained from the variable value table input from the variable replacing unit;
• and
• the NC program for variable-check writing unit stores the replaced predetermined unit of the program in the NC program for variable-check storage region.