GATE Overflow Test Series | Mixed Subjects | Test 4 | Question: 11

Question

Which of the following are possible with regard to processes in OS? (Mark all the appropriate choices)

• A. A child process running itself even when its parent process has finished execution.
• B. A process having an entry in the process table even after its execution being completed.
• C. A process changing its parent using appropriate system calls.
• D. A process having multiple parent processes at any time.

Answer 1

An orphan process is a computer process whose parent process has finished or terminated, though it (child process) remains running itself.

A zombie process or defunct process is a process that has completed execution but still has an entry in the process table as its parent process didn't invoke an wait() system call.

C and D are false.
Reference : https://unix.stackexchange.com/questions/193902/change-the-parent-process-of-a-process

Comments

https://en.wikipedia.org/wiki/Init

An orphan process is adopted by init process, wouldn't that count as changing process?

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The child process becomes orphan when the parent terminates, or killed, and then only child is adopted by init.

A child cannot kill it’s parent, also in order to change the parent, a child has to change it’s parent ID and also child ID in it’s parent’s process, which it can’t do as a child cannot change it’s parents variables.

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@Codered03 Totally missed “using appropriate system calls”, thanks for the clarification.

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this question may clear the Init ((orphan)) Part
4. Consider a parent process P that has forked a child process C. Now, P terminates while C is still
running. Answer yes/no, and provide a brief explanation.
(a) Will C immediately become a zombie?
(b) Will P immediately become a zombie, until reaped by its parent?
Ans:
(a) No, it will be adopted by init.
(b) Yes.

A process is called a zombie process, if it is terminated but it's entry still exists in the Process Tabl
Because it has to pass it's exit status to the the parent process.

Init will adopt only those processes for which there is no parent process that is currently alive (or a slot in the process table entry) is no more, but in your case, child has exited first
and it enters zombie state for the parent to collect the status of the created child process. Since the parent process of the child is alive very much ( in sleep mode ) init cannot
adopt that, and once the parent process terminates, child stats is collected and there is no need for the child process to remain as zombie and it becomes completely relieved.