CONTROLLER

PROBLEM TO BE SOLVED: To make a user program reproducible at the point of time after one- line editing was performed plural times while additionally changing a user program etc., consisting of modules when the user program is additionally changed. SOLUTION: When a source code 17 stored on a hard disk 7 is executed, a tool 1 reproduces the user program at the point of time after on-line editing was done plural times so as to restore the source code 17 stored on the hard disk 7 on a magnetic disk 6. Further, a run-time core 31 clears remaining variables to 0 when the variables of the source code 61 before the on-line editing are left at the time of the on-line editing of the source code 61 restored on the magnetic disk 6 from the hard disk 7.