GATE CS 2024 Set 1 | Question 25

MSQ · 1 mark

Which of the following process state transitions is/are NOT possible?

  1. Option A: Running to Ready
  2. Option B: Waiting to Running (correct)
  3. Option C: Ready to Waiting (correct)
  4. Option D: Running to Terminated

Answer

(B), (C)

Explanation

In the process state diagram the moves are: Ready to Running (dispatch), Running to Ready (preemption, for example when the time slice ends), Running to Waiting (an I/O request or a wait for an event), Waiting to Ready (the event completes) and Running to Terminated (exit).

  • Waiting to Running is not possible: when its event completes, a waiting process joins the ready queue, and only the scheduler can dispatch it from there.
  • Ready to Waiting is not possible: a process blocks only by doing something, such as requesting I/O, and a ready process is not executing.

Running to Ready and Running to Terminated are normal transitions, so A and D are possible.

Answer: B, C