PURPOSE: To automatically prepare the operation environment required for only the function used by each process out of auxiliary functions presented by a coprocessor with less overhead in the system where auxiliary functions are supported by the coprocessor.

CONSTITUTION: A stage 1 where coprocessor auxiliary functions are invalidated at the time of initializing a process, a stage 2 where an interrupt is generated if coprocessor auxiliary functions are used though being invalidated, a stage 3 where the operation environment for the use of coprocessor auxiliary functions is prepared at the time of generation of the interrupt, and a stage 4 where coprocessor auxiliary function are validated to re-execute the instruction which causes generation of the interrupt after arranging the operation environment of coprocessor auxiliary function are provided.