PURPOSE: To operate plural guest OSs comprehensively with an operation for real machine by conforming an interruption code to the operation in a system comprised of plural kinds of guest OSs, a virtual machine, and the real machine.

CONSTITUTION: The real machine 1101 notifies an operating command inputted from a CD 1401 to the virtual machine 1201 in the interruption code. The virtual machine 1201 simulates interruption in accordance with the kind of the guest OS and the interruption code and notifies them to the guest OSs #1-#3. The guest OS executes an OS command string in accordance with the operating command registered in advance dealing with the interruption code. In this way, the comprehensive operation of a computer system when it goes down can be performed with an easy operation, which reduces the burden on an operator.