help i am not kernel pls run for me
examples: getpid(), write() (which is called by printf())
how it works:
- user program invokes the library call
- library call places the system call number in a designated location (eg. register)
- library call executes a special instruction to switch modes (user → kernel)
- TRAP instruction
- now in kernel mode, the appropriate system call handler is determined (using the system call number)
- similar to vectored interrupt
- system call handler is executed → system call handler ended → library call returns to user program