PURPOSE: To execute the software on other central processing unit without rewrite by executing the instruction of other central processing unit as the program same as the specific instruction so as to manage it.

CONSTITUTION: An arithmetic section 1 reads a required data, stores the result of arithmetic operation, instructs the address of an instruction to be read next to a main storage control section 3 and executes the next instruction. Moreover, an instruction decoding/execution control section 2 discriminates identification additional information 6 of specific/other system instruction among the instructions read from the main storage device 4. In the case of instruction of the other system, a required program is selected among simulation execution program groups 10W12 specifying the operation relating to the said prepared instruction code on the main storage device 4 in advance by the said instruction code to switch the execution. When the execution is finished, the control is transferred to the instruction to be executed next to the instruction included in the program of the other central processing units AWC.