 In 1989 with SVR4, a new call "waitid" has been introduced that returns all bits from the "exit" call in a structure called "siginfo_t" in the structure member "si_status".Waitid is a mandatory part of the POSIX standard since 2001.When a child process terminates, it becomes a "zombie process," and continues to exist as an entry in the system process table even though it is no longer an actively executing program.