What are zombie and orphan processes?

Zombie process: child has terminated but parent hasn't read its exit status (via wait()). Entry remains in process table with exit code. Zombies consume PID resources. Fix: parent should wait() for children, or use signal handler for SIGCHLD. Orphan process: parent terminates before child. The init process (PID 1) adopts orphans and will wait() for them. Orphans continue normal execution; zombies are already dead but not reaped.