With 3 initially empty frames, how many page faults does FIFO page replacement cause for the reference string 2, 4, 1, 4, 3, 2, 5, 4, 1, 2?
Correct answer B. 9
Topic / 93 questions
Operating Systems MCQs
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In the dining philosophers problem, what can happen if every philosopher picks up the left chopstick at the same moment?
Correct answer D. Deadlock, because each waits forever for the right chopstick
In a resource-allocation graph where every resource type has exactly one instance, what does a cycle indicate?
Correct answer B. A deadlock definitely exists
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Which of these is NOT one of the four necessary (Coffman) conditions for deadlock?
Correct answer C. Preemption of resources
What does an atomic test-and-set instruction do?
Correct answer A. Returns the old value of a memory word and sets it to true as one indivisible operation
A low-priority task holds a lock needed by a high-priority task, and a medium-priority task keeps preempting the low one. What is this problem called?
Correct answer C. Priority inversion
In the first readers-writers problem, which party may starve?
Correct answer B. Writers
What does a monitor guarantee about the procedures defined inside it?
Correct answer D. Only one process can be active inside the monitor at a time
How does a mutex lock differ from a binary semaphore?
Correct answer A. A mutex has an owner and should be released only by the thread that locked it, while a semaphore can be signalled by any thread
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In the bounded-buffer producer-consumer problem with n slots using semaphores mutex, empty and full, what are their initial values?
Correct answer D. mutex = 1, empty = n, full = 0
A counting semaphore S starts at 7. Then 10 wait (P) operations and 4 signal (V) operations are performed. Under the definition where the value can go negative, what is the final value of S?
Correct answer D. 1
What is the main disadvantage of a spinlock?
Correct answer B. A waiting thread wastes CPU cycles by looping until the lock becomes free
When does non-preemptive scheduling make a scheduling decision?
Correct answer D. Only when the running process terminates or switches to the waiting state
Which technique prevents starvation of low-priority processes in priority scheduling?
Correct answer B. Aging, which gradually raises the priority of processes that wait a long time
What happens to round robin scheduling when the time quantum is made very large, longer than every CPU burst?
Correct answer D. It behaves the same as FCFS
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In a multilevel feedback queue scheduler, what typically happens to a process that uses its entire time slice at a high-priority level?
Correct answer B. It is moved down to a lower-priority queue
Two threads each run count = count + 1 on a shared variable without synchronisation, and the final value is sometimes wrong. What is this called?
Correct answer C. A race condition
Which three requirements must a correct solution to the critical-section problem satisfy?
Correct answer A. Mutual exclusion, progress and bounded waiting
Peterson’s solution to the critical-section problem for two processes uses which shared variables?
Correct answer C. A boolean array flag[2] and an integer turn
Compared with creating a new process, why is creating a thread generally cheaper?
Correct answer C. A thread shares its process's address space and resources, so far less must be allocated