PURPOSE: To prevent the unjust copying of a program by changing the instruction code of a hardware system even in the same machine type by the recognition code which discriminates the hardware uniquely and changing the program in accordance with this change.

CONSTITUTION: Each hardware system 1 is provided with a recognition code 11 which discriminates the hardware system 1 uniquely and a decoder 12 which recognizes a recognition code setting instruction 10. An object program 21 executed by the hardware system 1 is provided with an area 21a where the positions of the recognition code setting instruction 10 are indicated. when the object program 21 is converted to a program structure matched to the hardware system 1 by a converting program 22, the recognition code 11 i set to the discrimination code part 10b of the recognition code setting instruction 10, and the contents of the area 21a are erased when this processing for all recognition code setting instructions 10 is terminated.