GATE CS 2020 Q12 — CPU Scheduling

Let us analyze each statement based on the standard process state transition diagram in a preemptive scheduling system:

1. I. Running to Ready: True. In preemptive scheduling, a running process can be interrupted (e.g., due to time quantum expiration or a higher priority process arriving) and moved back to the ready state.
2. II. Ready to Running: True. When the CPU scheduler selects a process from the ready queue, it is dispatched and moves from the ready state to the running state.
3. III. Blocked to Running: False. A blocked (or waiting) process cannot directly transition to the running state. It must first transition to the ready state once its I/O or event completes, and wait for the scheduler to dispatch it.
4. IV. Blocked to Ready: True. When the event or I/O operation that the blocked process was waiting for completes, the process moves to the ready state.

Thus, statements I, II, and IV are TRUE, which corresponds to option C.