OS

Zombie: A process that has terminated, but whose parent has not yet called wait() , is known as a zombie process. All processes transition to this state when they terminate, but generally they exist as zombies only briefly. Once the parent calls wait() , the process identifier of the zombie process and its entry in the process table are released.

Orphan: If a parent did not invoke wait() and instead terminated, thereby leaving its child processes as orphans. Linux and UNIX address this scenario by assigning the init process as the new parent to orphan processes. The init process periodically invokes wait() , thereby allowing the exit status of any orphaned process to be collected and releasing the orphan’s process identifier and process-table entry.