 Under Unix and Unix-like operating systems, a process is started when its parent process executes a "fork" system call.The parent process may then wait for the child process to terminate, or may continue execution (possibly forking off other child processes).When the child process terminates ("dies"), either normally by calling "exit", or abnormally due to a fatal exception or signal (e.g., SIGTERM, SIGINT, SIGKILL), an exit status is returned to the operating system and a SIGCHLD signal is sent to the parent process.