Which scheduler decides which jobs are admitted into memory to control the degree of multiprogramming?
Correct answer A. Long-term (job) scheduler
Topic / 93 questions
Operating Systems MCQs
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Processes P1, P2 and P3 all arrive at time 0 with CPU burst times of 10, 4 and 2 ms and are served FCFS in the order P1, P2, P3. What is the average waiting time?
Correct answer D. 8 ms
Processes P1, P2 and P3 all arrive at time 0 with CPU burst times of 10, 4 and 2 ms. What is the average waiting time under non-preemptive SJF scheduling?
Correct answer D. 2.67 ms
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Processes P1, P2, P3 and P4 arrive at times 0, 1, 3 and 4 ms with burst times 9, 5, 2 and 6 ms. What is the average waiting time under preemptive SJF (shortest remaining time first)?
Correct answer C. 4.75 ms
Processes P1, P2 and P3 arrive at time 0 in that order with burst times 10, 5 and 8 ms. Using round robin with a time quantum of 4 ms, what is the average waiting time?
Correct answer D. 12.67 ms
Processes P1, P2 and P3 arrive at 0, 2 and 4 ms with burst times 5, 3 and 1 ms and are scheduled FCFS. What is the average turnaround time?
Correct answer D. 5.33 ms
Processes P1, P2 and P3 arrive at time 0 in that order with burst times 5, 3 and 1 ms. Under round robin with a quantum of 2 ms, what is the average turnaround time?
Correct answer C. 7.33 ms
SJF predicts the next CPU burst with an exponential average. If the weight is 0.5, the previous prediction was 10 ms and the actual last burst was 6 ms, what is the next prediction?
Correct answer C. 8 ms
Several short I/O-bound processes repeatedly wait behind one long CPU-bound process under FCFS. What is this effect called?
Correct answer D. Convoy effect
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Four processes arrive at time 0 with burst times P1 = 6, P2 = 2, P3 = 4, P4 = 3 ms and priorities 3, 1, 4, 2, where a smaller number means higher priority. What is the average waiting time under non-preemptive priority scheduling?
Correct answer D. 4.5 ms
Which process state transition is caused by a timer interrupt in a preemptive system?
Correct answer D. Running to ready
What is a system call?
Correct answer A. The interface through which a user program requests a service from the operating system kernel
What is the difference between an interrupt and a trap?
Correct answer C. An interrupt comes from hardware such as a device, while a trap is a software-generated event such as a system call or division by zero
What does the interrupt vector hold?
Correct answer C. The addresses of the interrupt service routines for the various devices
Why does an operating system program a hardware timer to interrupt the CPU periodically?
Correct answer D. To stop a user program from keeping the CPU forever, so the kernel regains control
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Which kernel design moves services such as file systems and device drivers into user-space processes that communicate by message passing?
Correct answer C. Microkernel
What is the key difference between a program and a process?
Correct answer B. A program is passive code stored on disk, while a process is a program in execution with its own state
Which of these is NOT normally stored in a process control block (PCB)?
Correct answer C. The source code of the program
A running process issues a disk read and must wait for it to finish. Which state does it move to?
Correct answer B. Waiting (blocked)
What is a context switch?
Correct answer D. Saving the state of the running process and loading the saved state of another process