📝 Semaphores

📖 From Operating System • 5. Process Synchronization • 50 questions available

Practice MCQs for Semaphores. Test your knowledge with carefully crafted questions across easy, medium, and hard difficulty levels.

🔄 Last updated: 2026-07-09

Easy Questions

Medium Questions

Hard Questions

Q1. What is a semaphore in the context of process synchronization?

🔹 A. A hardware register.

🔹 B. An integer variable accessed only through atomic operations.

🔹 C. A boolean flag for mutual exclusion.

🔹 D. A queue of waiting processes.

💡 Difficulty: easy | ✅ Correct: B

Q2. What is a critical requirement for the `wait()` and `signal()` operations on a semaphore?

🔹 A. They must be executed in user mode.

🔹 B. They must be executed atomically.

🔹 C. They must be called in pairs.

🔹 D. They must be called from the same process.

💡 Difficulty: medium | ✅ Correct: B

Q3. What is the effect of executing `wait(S)` on a semaphore with value 0?

🔹 A. The semaphore value becomes -1.

🔹 B. The semaphore value becomes 1.

🔹 C. The process busy-waits and the semaphore value remains 0 until it becomes positive.

🔹 D. The semaphore value becomes 0.

💡 Difficulty: hard | ✅ Correct: C

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