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. Interface between user space and kernel space.

Execution Path

User Process

Sets up arguments and executes a specific instruction (e.g., TRAP or SYSCALL).

Hardware

Triggers a mode switch to kernel mode and jumps to a predefined handler.

Kernel

Verifies arguments, executes the requested service, and places the result in a register.

Return

Kernel executes return-from-trap instruction, switching back to user mode.