Computer operating with battery and its initial setting method

PURPOSE: To obtain an initial setting method which is improved for the computer which can operate on plural operation systems such as DOS and OS/2 running in real mode and protect mode by enabling a power source management interruption according to which of the operating systems DOS and OS/2 is loaded in a main memory. CONSTITUTION: On the completion of POST 20, an operating system is loaded according to a setup. Namely, when the DOS is the requested operating system, it is loaded in the main memory 16 so that the processor 12 executes it. When it is judged that an array of specific codes or routines is executed first after the power source is turned on or the system is rebooted, the power source management interruption by a controller 54 is allowed by setting an input gate connected to a line 52. Even when the processor is so set up as to operated with the OS/2, an interruption is similarly allowed.