Method of handling system calls to an operating system of a computer by system service routines stored as firmware

摘要

A computer has an external memory, and a CPU having an internal memory, typically a ROM, with an operating system being stored partly as firmware in the internal memory and partly as software in the external memory. When an operating-system function is requested, the computer checks whether or not the requested operating-system function is stored as firmware. If it is, the requested operating-system function is executed. If it is not, the software in the external memory is searched for the requested operating system function.