System Calls

Any API function, internally, invokes a system call. The OS program that connects API function calls to system calls is the system call interface. When a function is called, the interface looks up the corresponding number of the system call based on which function was called.

The system call interfaces look the open() system call up. The digrams describes the following stages: (1) some app calls the open() function, (2) the operating system checks what the serial number of the open() function is, (3) this serial number represents a lower-level implementation of the open() function, and the operating system uses it to run that open() system call, (4) after the system call finishes running, the control returns back to the user application.

Invoking the open() system call. Taken from Bell, John T. "Operating-System Structures." University of Illinois, Chicago.

These notes by Miriam Briskman are licensed under CC BY-NC 4.0 and based on sources.