Abstract: The emulation of a first system disk drive on a second processing system including a second system user level process including first system user and executive tasks issuing disk input/output requests. An emulator level is interposed between the second system user level process and a kernel level and includes a pseudo device driver corresponding to the first system disk drive and the kernel level includes a kernel process corresponding to the pseudo device driver and emulating the disk drive. The pseudo device driver and the kernel process execute in a second system process to emulate the operations of the disk drive and the kernel process emulating the disk drive is a file input/output process. The pseudo device driver includes a pseudo device queue, a return queue and a queue manager responsive to first system disk input/output instructions and to completed disk operations.

Abstract: An emulator executes on a second data processing system as a second system user level process including a first system user level program, a first system executive program, and first system user and executive tasks. An emulator level is interposed between the second system user level process and a kernel level and contains pseudo device drivers. Each pseudo device driver corresponds to a first system input/output device. The kernel level includes kernel processes, each kernel process corresponding to a pseudo device driver. The second system hardware platform includes a plurality of second system input/output devices, wherein each second system input output device corresponds to a kernel process. Each combination of a pseudo device driver, a corresponding kernel process and a corresponding second system input/output device executes in a second system process and emulates the operations of a corresponding first system input/output task and the corresponding first system input/output device.