PURPOSE: To cope with the kind expansion of application instructions as it is without altering software or hardware.

CONSTITUTION: A user memory 13 is stored with assigned instructions, which are selected by a user among selectable instructions and assigned to object codes, in table form in addition to a user program. An MPU NO inputs the table from the user memory 13 and also writes jump destination addresses for the object codes of the assigned instructions in a RAM 12 in table form by referring to the previously stored table of the selectable instructions. When the user program is executed, the MPU 10 once reading an object code in the user program fetches an assigned instruction from a jump destination address made to correspond to the object code by referring to the table in the RAM 12 and executes the instruction.