Topic: Operating Systems
Which of the following transitions is not possible between the process states shown below?
States: Run, Ready, Waiting, Terminated
- A. Run $\rightarrow$ Ready
- B. Run $\rightarrow$ Terminated
- C. Run $\rightarrow$ Waiting
- D. Waiting $\rightarrow$ Run
Answer: D. Waiting $\rightarrow$ Run
Explanation: In standard process state models, a process in the 'Waiting' (or Blocked) state is waiting for an event like I/O completion. Once the event occurs, the process transitions to the 'Ready' state to be placed in the ready queue. It cannot transition directly from 'Waiting' to 'Run'; it must be selected by the CPU scheduler from the 'Ready' state.