A process is an instance of a running program. On POSIX-compatible systems each process is identified by a unique number called a PID (Process ID), associated with which is a collection of system resources for use by the program. These include:

New processes can be created by calling the fork function. They can terminate themselves by calling the exit function, or be terminated by receiving one of the signals SIGTERM, SIGINT, SIGQUIT or SIGKILL. Processes can be monitored using the ps or top commands.


Further reading