The term Zombie is used to describe a terminal condition of a thread or process. There is a strict operating system definition and two colloquial uses:

• The strict system definition refers to a process that has terminated but whose PTDA has been retained on the zombie queue (_pPTDAFirstZombie) because the process status byte (LISEG+0xa) indicates that its parent wishes to collect termination information through DosWaitChild. The dead child is retained on the zombie queue until either the parent dies or issues DosWaitChild.

• Zombie is also commonly used to refer to a terminating thread or process that has blocked after the application has returned to the operating system. Usually this implies a problem freeing memory because one or more pages have been long-term locked by a device driver.

• The third use of zombie refers to any process that is anonymous. Internal thread, VDMs, and terminating threads can be anonymous.

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