Zombie process

A zombie process is a term in computing which defines a process that exists but which has completed execution. A zombie process usually cannot be destroyed because it is the parent of one or more [child process]?es.

The term zombie process comes from the unix operating system. It takes its meaning from the common definition of zombie--a walking dead person. In Unix, the most common cause of a zombie, is where the process has exitted, but it's parent process has not yet done a "wait" system call for it. The book-keeping information for the zombie has to be retained so it can eventually be supplied to the parent when it does "wait". Typically, zombies that exist for more than a short period of time indicate a bug somewhere. The kind of zombie mentioned in the first paragraph does not occur in Unix and similar systems.