System Call
A system call is a mechanism used by an application to request a service from the operating system’s kernel.
Purpose: It allows user-level processes to request services of the kernel, which has privileged access to hardware and system resources.
Resources
Examples of system calls
- Reading or writing files,
- creating processes,
- communicating over networks
Are all system calls done through traps?
Yes, all system calls are triggered through traps (or equivalent mechanisms like software interrupts). Here’s why.
Major System Calls
read()mallocis (sometimes) a system call when you actually need more memory at runtime- malloc resides in user space, runtime C library
- the (sometimes) is because the underlying runtime C library can be smarter about how malloc is done to reduce the number system calls that the program does to request for more memory
