Semaphores 2 — Test 1

Correct Answer: B. B. Deadlock
Explanation: If a thread which had already locked a mutex, tries to lock the mutex again, it will enter into the waiting list of that mutex, which results in a deadlock. It is because no other thread can unlock the mutex.

Correct Answer: C. C. Can be accessed from multiple processes

Correct Answer: B. B. Binary & counting

Correct Answer: B. B. Must be accessed from only one process
Explanation: میوٹیکس (Mutex) کیا ہے؟ میوٹیکس (جس کا پورا نام Mutual Exclusion ہے) آپریٹنگ سسٹم میں ایک ایسا تالا (Lock) ہے جو یہ یقینی بناتا ہے کہ کمپیوٹر کا کوئی بھی خاص حصہ یا ڈیٹا (Shared Resource) ایک وقت میں صرف ایک ہی پروگرام یا تھریڈ (Thread) استعمال کرے۔

Correct Answer: B. B. 2
Explanation: P represents Wait and V represents Signal. P operation will decrease the value by 1 every time and V operation will increase the value by 1 every time. In semaphore operations:P Operation (Wait/Down): Decrements the value of the semaphore ($S = S - 1$).V Operation (Signal/Up): Increments the value of the semaphore ($S = S + 1$).Step-by-step:Initial Value: $7$After 20 P operations: $7 - 20 = -13$After 15 V operations: $-13 + 15 = 2$

Correct Answer: A. A. 1

Correct Answer: C. C. Four
Explanation: Here are the possible ways in which statements from A and B can be interleaved. A1 A2 B1 B2: X = 11 A1 B1 A2 B2: X = 6 A1 B1 B2 A2: X = 10 B1 A1 B2 A2: X = 10 B1 A1 A2 B2: X = 6 B1 B2 A1 A2: X = 12.

Correct Answer: A. A. One
Explanation: The semaphore T ensures that all the statements from A finish execution before B begins. So now there is only one way in which statements from A and B can be interleaved: A1 A2 B1 B2: X = 11.

Correct Answer: B. B. Ipc mechanisms

Correct Answer: B. B. Bounded waiting
Explanation: A spinlock is a mutual exclusion mechanism that uses busy-waiting (looping) instead of sleeping, making it ideal for very short critical sections in multi-core systems.