PURPOSE: To execute a program even if a specified program is not connected by deciding whether a unit program specified by control transfer information is connected or not, and when disconnected, restoring control to the original program.

CONSTITUTION: A control transfer information storing means 1 stores control transfer information in a control transfer information storing part 11 and starts a deciding means 2 by a deciding means starting part 12. The means 2 decides whether the unit program specified by the control transfer information is connected or not by a specified program connection control part, and when connected, transfers the control to the specified program by a specified program control transferring part. If disconnected, a control restoring means 3 is started by a control restoring means starting part. The means 3 restores the control to the original program immediately before the starting of the means 1 by an original program control restoring part.