CUET PG MCA Operating System Previous Year Questions (PYQs) – Page 1 of 4

• FCFS (First Come First Serve): Executes in the order processes arrive, no burst-time consideration.

• SJF (Shortest Job First): Picks the process with the least CPU burst time → minimizes average waiting time.

• Round Robin: Allocates equal time slices (quantum) cyclically, ignoring burst length.

• Priority Scheduling: Selects based on priority value, not burst time (though burst time can be used as a priority heuristic).

For a deadlock to occur in a system, the following Coffman’s conditions must all hold together:

1. Mutual Exclusion – At least one resource must be held in a non-shareable mode.

2. Hold and Wait – A process holding resources is waiting for additional resources.

3. No Preemption – Resources cannot be forcibly taken away; they are released only voluntarily.

4. Circular Wait – A closed chain of processes exists, each waiting for a resource held by the next process in the chain.

If even one of these is not satisfied, deadlock cannot occur.

Use of semaphores ✅

Because the Dining Philosopher problem is a classical synchronization problem, and it is solved using semaphores / monitors / mutex locks.

• Overlays → related to memory management, not correct.

• Mutual exclusion → is a requirement, but the standard answer in MCQs is semaphores.

• Bounded waiting → is a condition, not the actual solution technique.

So the correct choice from the given options is "Use of semaphores."

Let’s analyze the options:

1. Process termination ✅

   • This is indeed a way to recover from a deadlock after it has already occurred (kill one or more processes to break the cycle).

2. Non-preemption of resources ❌

   • This is a deadlock prevention method, not recovery.

3. Banker’s algorithm ❌

   • This is a deadlock avoidance technique, not recovery.

4. Circular wait ❌

   • This is one of the necessary conditions for deadlock, not a recovery method.

Using LRU with 3 frames on the string
7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3, 2
gives page faults at: 7, 0, 1, 2, 3, 4, 2, 3, 0 → 9 faults.

Explanation:

• SSTF (Shortest Seek Time First): Always serves the request that requires the minimum head movement from the current head position.

• LOOK/SCAN: Move in one direction (like elevators), serving requests along the way.

• FCFS: Serve requests in the order they arrive.

✅ Hence, SSTF is the correct choice.

The general structure of a process with critical section is:

1. Entry section → request entry into the critical section.

2. Critical section → perform the critical task.

3. Exit section → leave and update status.

4. Remainder section → execute non-critical code.

In MS-DOS, the layering from innermost to outermost is:

1. ROM BIOS Device Drivers (lowest-level hardware interaction)

2. MS-DOS Device Drivers (software drivers loaded by OS)

3. Resident System Program (command.com, kernel parts)

4. Application Program (user programs)