System Call

operating-systems

Definition

System Call

A System Call is a programmatic request by a user process for a service performed by the kernel. It serves as the interface between user space and kernel space.

Execution Path

1. User Process: Sets up arguments and executes a specific instruction (e.g., TRAP or SYSCALL).
2. Hardware: Triggers a mode switch to kernel mode and jumps to a predefined handler.
3. Kernel: Verifies arguments, executes the requested service, and places the result in a register.
4. Return: The kernel executes a return-from-trap instruction, switching back to user mode.