GATE IT 2006 | Question: 13

Question

The process state transition diagram of an operating system is as given below.

Which of the following must be FALSE about the above operating system?

• A. It is a multiprogrammed operating system
• B. It uses preemptive scheduling
• C. It uses non-preemptive scheduling
• D. It is a multi-user operating system

Comments

Similar -> https://gateoverflow.in/1318/gate2009-32

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Someone just draw the diagram of preemptive and non preemptive transition state. It will surely clear a few doubts here.

Answer 1

Answer (B).

Explanation:

• A. It is a multiprogrammed operating system.
  Correct, it has ready state. We can have multiple processes in ready state here so this is Multiprogrammed OS.
   
• B. It uses preemptive scheduling
  False : There is no arrow transition from running to ready state. So, this is non preemptive.
   
• C. It uses non-preemptive scheduling
  True.
   
• D. It is a multi-user operating system.
  We can have multiple user processes in ready state. So, this is also correct.

Comments

A few minor corrections:

1. Just because ready state is present does not mean that the given OS is a multi-programmed OS. The presence of both the ready state (multiple processes may reside in the main memory at the same time), and the fact that a process is blocked when waiting for the release of the required resources, or when waiting for I/O completion (in which case some other process may be fetched now and executed), together implies that the given OS may be a multi-programmed OS. As the question ask for the option that must be FALSE, we pass over option \((A)\).
2. Option \((D)\) is not correct, it’s just that it’s possible, i.e., multiple processes from multiple users may or may not be in ready state. As the question ask for the option that must be FALSE, we pass over option \((D)\).

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Can't you guys see the transition from running to ready state. Its clearly there, it goes to i/o then to ready state. While it's doing that CPU should be given to some other process or else there was no need to go back to ready state again. I don't know why my guide also says the answer is B but I believe the answer is C. It uses non-preemtive scheduling is a false statement as there is a clear transition from running to ready state, so its a preemptive scheduling.

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@PreyumKr Consider processes that are entirely CPU bound, requiring no I/O or competing for resources (except CPU). That’s possible, right? Just because there is an edge from running state to blocked state doesn’t mean that every process has to make that transition. In that case, would you still have a preemptive OS? A preemptive OS should make provisions for all sort (and sequence) of processes, right?

Answer 2

B is False. If it were a preemptive scheduling then there would have been a transition from Running state to Ready state.