PURPOSE: To realize automatic cut-off with use of a simple circuit, by controlling a system program of an external storage means to write into a volatile memory based on a program of an internal nonvolatile memory when the power source is applied.

CONSTITUTION: An internal nonvolatile memory 1A that performs a bootstrap sets and stores a cut-off instruction word after a program by which a prescribed operation is carried out after a power source is applied. Then a system program is controlled to write into a volatile memory 1B from an external storage device 12 and based on the program of the memory 1A during a period from the application of power source to the detection of the cut-off instruction word. When the reading of the cut-off instruction word is detected, the memory 1A is cut off to be jumped to a desired program of the memory 1B.