A computer system of a multi-operation-system (multi-OS) has a main memory having a memory area for a first OS and a memory area for a second OS, both the areas being independent from each other, and a plurality of I/O devices divisionally allocated to the first OS and the second OS. The first OS is loaded in the first OS memory area, and thereafter when the first OS is operated, the second OS is loaded in the second OS memory area and initialized. When the first OS is operated, the first OS hardware resources and the second OS hardware resources are registered by the first OS. Thereafter when the first OS is operated, the first OS inhibits the registration of an interrupt number already allocated to the second OS I/O device. In response to an interrupt request from a second OS I/O device, the second OS starts operating.

A computer system of a multi-operation-system (multi-OS) has a main memory having a memory area for a first OS and a memory area for a second OS, both the areas being independent from each other, and a plurality of I/O devices divisionally allocated to the first OS and the second OS. The first OS is loaded in the first OS memory area, and thereafter when the first OS is operated, the second OS is loaded in the second OS memory area and initialized. When the first OS is operated, the first OS hardware resources and the second OS hardware resources are registered by the first OS. Thereafter when the first OS is operated, the first OS inhibits the registration of an interrupt number already allocated to the second OS I/O device. In response to an interrupt request from a second OS I/O device, the second OS starts operating.

A general purpose computer operating system is run using a real time operating system. A real time operating system is provided for running real time tasks. A general purpose operating system is provided as one of the real time tasks. The general purpose operating system is preempted as needed for the real time tasks and is prevented from blocking preemption of the non-real time tasks.

A debugger that is multi-task aware and capable of providing symbolic support to a graphical user interface (GUI) is disclosed. The debugger disclosed communicates with a multi-tasking kernel nested within a driver of the operating system within the 0 privilege level. The multi-tasking kernel distinguishes among the rest of its environment where a graphical user interface executes the driver tasks being debugged. The multi-tasking kernel, in cooperation with the debugger runs each element on a different thread of the same machine, thereby allowing the debugger and the driver tasks being debugged to continue to run without stopping operation of either the graphical user interface or the operating system associated with the graphical user interface.

A physical memory of a single computer is divided for each of a plurality of operating system (OS). A first OS is first loaded into the computer and runs. A multi-OS management program common to a plurality of OSs is incorporated into a virtual address space of the first OS as a device driver of the first OS. The multi-OS management program incorporated as the device driver is rearranged in a memory area shared by OSs so that the multi-OS management program has the same virtual address in any OS. In this state, the second OS program itself is loaded in the virtual address space of the second OS by execution of the multi-OS management program in the first OS. Execution of the multi-OS management program is switched from the multi-of management program in the first OS to the multi-OS management program in the second OS. Then, the second OS is started by execution of the multi-OS management program in the second OS to thereby run the plurality of OSs on the single computer.