System Calls
A system call is the mechanism through which a user‐level process requests a service from the operating system’s kernel. It provides a controlled interface between user programs and hardware or kernel‐mode services. Typical examples include file operations (open, read, write, close), process control (fork, exec, exit), and I/O operations .
| Type | Purpose | Examples |
|---|---|---|
| Process Control | Create, terminate, and manage processes; synchronize and communicate. | fork(), exec(), exit(), wait(), kill() |
| File Management | Create, delete, read, write, and reposition files; get/set metadata. | open(), read(), write(), lseek(), stat() |
| Device Management | Request and release device access; perform I/O; get/set attributes. | ioctl(), read(), write(), mmap(), chmod() |
| Information Maintenance | Query or set system data and process attributes. | getpid(), alarm(), time(), gettimeofday(), uname() |
| Communication | Establish and manage interprocess communication channels. | pipe(), shmget(), msgsnd(), recv(), socket() |
| Protection | Control access permissions for files, devices, and memory regions. | chmod(), umask(), setuid(), mprotect() |