OS OBJECTIVE QUESTIONS

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OS OBJECTIVE QUESTIONS

Which one of the following is Little’s formula

Where ‘n’ is the average queue length, ‘W’ is the time that a process waits

1)n=Lambda*W 2)n=Lambda/W 3)n=Lambda^W 4)n=Lambda*(W-n) Answer:1

--- A CPU scheduling algorithm determines an order for the execution of its scheduled processes. Given ‘n’ processes to be scheduled on one processor, how many possible different schedules are there?

1) n! 2) n*n 3) 1 4) log n Answer: 1

--- CPU scheduling is the basis of ———– operating systems

1) Batch operating systems 2) Real time OS 3) Multiprogramming 4) Mono programming Answer:3 --- The SJF algorithm

1) executes first the job that last entered the queue 2) executes first the job that first entered the queue 3) executes first the job with the least processor needs 4) executes first the job that has been in the queue already Answer:3

--- Which scheduling policy is most suitable for a time shared operating systems?

1) SJF 2) RR 3) FCFS 4) Elevator Answer:2

--- Scheduling is

1) allowing job to use the processor 2) unrelated to performance conditions

3) quite simple to implement, even on large frames 4) the same regardless of the purpose of the system Answer:1

--- Context Switching is

1) Part of spooling 2) part of polling

3) part of interrupt handling 4) part of interrupt servicing Answer: 3

The dispatcher

1) actually schedules the task to the processor 2) is always very small

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4) should be used only on large computers Answer: 1

--- 126) Race condition results for the following

1) all processes 2) co-operating processes 3) competing processes 4) none Answer:3 --- Which of the following is not related to disk scheduling ?

1) transfer time 2) waiting time 3) seek time 4) rotational latency Answer:1 --- Which of the following is not related to the disk access

1) Wait Time 2) Transfer Time 3) seek time 4) Latency Time Answer:2

--- Consider the following reference strings {0, 2, 4, 1, 1, 4, 5, 7} {2, 3, 2, 5, 6, 3, 2, 6} The FIFO page replacement algorithm with 3 frames would give lesser number of faults for

1) Reference string I 2) Reference string II

3) Both will have the same number of faults 4) Can’t determine from the given data Answer: 2

--- Scheduling is ________

1) allows processor to use the jobs 2) Not required in uni processor system 3) Allowing jobs to use the processor 4) None.

Answer: 3

--- In which of the following scheduling schemes does context switching never take place.

1) Round robin 2) SJF

3) FCFS 4) Priority Answer: 3

In multilevel queue scheduling (CPU scheduling) arrange the following in the order lowest to highest priority. a) Interactive process b) Batch process c) System process d) Student process 1) a, b, c, d 2) d, c, b, a

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3) c, a, b, d 4) c, b, a, d Answer: 3

--- Belady’s Anomaly is present in _________

1) LIFO 2)FIFO 3) FCFS 4)SJF Answer:2

--- FCFS scheduling is the simplest algorithm, but it can cause short process to wait for very long processes. True/False

Answer: True

--- In which of the following scheduling schemes does context switching take place.

1) SJF 2) FCFS 3) Priority 4) both 1 and 3 Answer: 4

--- Which of the following is not a CPU scheduling algorithm?

1) SCAN 2) SJF 3) FCFS 4) Round robin Answer: 1

--- Process A has arrived in the system by time 0 and requires 5 time units in the CPU, process B has arrived by time 1 and requires 3 time units, process C has arrived by time 2 and requires 1 time unit. Assuming negligible processes switching time, and that all processes are CPU bound and that a new quantum starts whenever a process finishes, the average time for Round robin (Q=3) is

___________

1) 3.33 2) 2.33 3) 2.89 4) 4.67 Answer: 1

--- Which of the scheduling algo gives the minimum average waiting time for a given set of processes? 1) FCFS 2) SJF 3) Round Robin 4) Priority

Answer: 2

--- 83) Forcible removal of a resource from a process is possible through _____

1) Scheduling 2) Preemption 3) Dispatching 4) None Answer: 2

Which of the following gives control of the CPU to the process selected by short term scheduler? 1) Context switching 2) Thread 3) Interrupt 4) Dispatcher

Answer: 4

--- Which of the following is strictly preemptive?

1) FCFS 2) Priority 3) Round Robin 4) SJF Answer: 3

--- The performance of round robin algorithm depends on

1) Preemption 2) Time Quantum 3) Non-preemption 4) Priority Answer: 2

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--- The following are the processes and their burst time:

P1 : 6, P2 : 8 P3 : 7 P4 : 3.. The average turn around time if SJF is used is ____mille seconds

1) 7 2) 13 3) 19 4) 7.6

Answer: 2

--- Allocate the smallest hole that is big enough , is which type of fit in dynamic storage allocation problem.

1) First fit 2) Best fit 3) Worst fit 4) None Answer: 2

--- Round robin algorithm is suitable for which type of systems?

1) Real time systems 2) Embedded 3) Multiprogramming 4) Time sharing Answer: 4

---The major problem with priority scheduling algorithm is _________.

1) Indefinite blocking

2) Takes large turnaround time 3) Deadlock occurs

4) All the above Answer: 2

--- If the time quantum is very big in round robin CPU scheduling algorithm, then it acts as

1) SJF scheduling 2) FCFS 3) Priority 4) SJF with preemption Answer: 2

--- Medium term scheduler is based on

1) Scroll in, scroll out 2) Wrap in, wrap out 3) Swap in, swap out 4) Fetch in, fetch out Answer: 3

In which of the following context switching never takes place?

1) SJF 2) Round robin 3) Preemptive policy 4) None Answer: 1

--- The hardware mechanism that enables a device to notify the CPU is called _______.

1) Interrupt 2) Polling 3) System call 4) None Answer: 2

--- Round robin scheduling algorithm is suitable for Time sharing systems. True/ False

Answer: True

--- _______ selects the process from secondary storage and loads them into memory for execution. 1) Medium term scheduler

2) Short term scheduler 3) Long term scheduler

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4) None Answer: 3

--- To maximize CPU utilization and throughput we should maximize turnaround time and minimize waiting time. True/ False?

Answer: False

Exp: we should minimize turnaround time and minimize waiting time.

--- The function of resident monitor is Memory management. True/ False

Answer: False

Expl: The function of resident monitor is Automatic job scheduling.

--- Round robin scheduling is essentially the preemptive version of ________.

1) FIFO 2) Shortest job first 3) Shortest remaining 4) FCFS Ans: 1

--- If the Disk head is located initially at 32, find the number of disk moves required with FCFS if the disk queues of I/O blocks requests are 98,37,14,124,65,67.

1) 310 2) 324 3) 315 4) 321

Ans:- (4)

--- FIFO scheduling is ________.

1) Preemptive 2) Non Preemptive 3) Deadline 4) Fair share Ans: - 2

Using Priority Scheduling algorithm, find the average waiting time for the following set of processes given with their priorities in the order: Process : Burst Time : Priority respectively . P1 : 10 : 3 , P2 : 1 : 1 , P3 : 2 : 4 , P4 : 1 : 5 , P5 : 5 : 2.

1) 8 ms 2) 8.2 ms 3) 7.75 ms 4) 3 ms Ans: 2

--- 103) Which of the following disk scheduling techniques has a drawback of starvation?

1) SCAN 2) SSTF 3) FCFS 4) LIFO

Ans:- 2

--- Which of the following is a criterion to evaluate a scheduling algorithm?

1) CPU Utilization: Keep CPU utilization as high as possible. 2) Throughput: number of processes completed per unit time.

3) Waiting Time: Amount of time spent ready to run but not running. 4) All of the above

Ans: - 4

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Which of the following is not a disk scheduling algorithm?

1) SCAN 2) Elevator / LOOK 3) FCFS 4) Working set Ans: 4

--- Which of these scheduling algorithms allows a process to move up and down between queues? 1) Round robin

2) First-Come, First-Served scheduling 3) Multilevel feedback queue scheduling 4) Priority scheduling

Ans:- 3

--- If a new process arrives with CPU burst time less than remaining CPU burst time of

currentexecuting process, preempt. This scheduling algorithm is known as ____________. 1) Shortest-Job-First 2) Priority 3) FCFS 4) None of the above Ans :- 1

--- Which of these is not a part of the process scheduler?

1. Context Switch

2. Long, medium and short term scheduler 3. Dispatcher

4. Program Control Ans:- 4

The ready list in an operating system contains jobs ________. 1) waiting for I/O

2) being executed by the processor

3) waiting for the processor to be allotted to them 4) waiting for input only

Ans:- ( 3)

--- Round robin scheduling ________.

1) Is quite complex to implement

2) Allows interactive tasks quicker access to the processor 3) Allows processor bound tasks more time in the processor 4) Gives each task the same chance at the processor

Ans 4

--- Which of these scheduling algorithms allows a process to move up and down between queues? 1) Round robin

2) First-Come, First-Served scheduling 3) Multilevel feedback queue scheduling 4) Priority scheduling

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--- In a process scheduling, the mechanism for scheduling and policy can be set by __ and________ respectively.

1) Kernel & user process 2) User Process & threads 3) Shell & Kernel

4) Kernel & Threads Ans:- 1

--- ________ scheduler selects the jobs from the pool of jobs and loads into the ready queue.

1) Long term 2) Short term 3) Medium term 4) None of the above Ans: - 1

--- Which one of the following is true for a CPU having a single interrupt request line and a single interrupt grant line?

1) Neither vectored interrupt nor multiple interrupting devices are possible.

2) Vectored interrupts are not possible but multiple interrupting devices are possible 3) Vectored interrupts and multiple interrupting devices are both possible.

4) Vectored interrupt is possible but multiple interrupting devices are not possible Answer: 2

Which of the process scheduling algo do you expect to produce the smallest average waiting time 1) SJF 2) FCFS 3) round-robin 4) All the above

Answer:1

--- A disc queue with requests for I/O to blocks on cylinders

98, 183, 37, 122, 14, 124, 65, 67

If the head is presently at 53rd cylinder, what will be the total number of cylinders traversed if we are using SCAN disc scheduling algorithm.

1) 152 2) 252 3) 352 4) 462

Answer: 2

--- A disc queue with requests for I/O to blocks on cylinders.

98, 183, 37, 122, 14, 124, 65, 67

If the head is presently at 53rd cylinder, what will be the total number of cylinders traversed if we are using C-SCAN disc scheduling algorithm.

1) 182 2) 282 3) 382 4) 482 Answer: 3

98, 183, 37, 122, 14, 124, 65, 67

If the head is presently at 53rd cylinder, what will be the total number of cylinders traversed if we are using C-LOOK disc scheduling algorithm.

1) 155 2) 255 3) 355 4) 455

Answer: 3

--- In which disc scheduling algorithm the head traverses to the extreme end cylinders.

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Answer: 3

--- In which disc scheduling algorithm the head traverses to the nearest available cylinder.

1) FCFS 2) SSTF 3) SCAN 4) C-LOOK

Answer: 2

--- In which disc scheduling algo the head traverses to the first cylinder encountered in the given order. 1) FCFS 2) SSTF 3) SCAN 4) C-LOOK

Answer: 1

--- In which disc scheduling algorithm the head traverses till one end then returns directly to the other end before encountering any other cylinder.

1) FCFS 2) SSTF 3) C-SCAN 4) C-LOOK

Answer: 3

--- C-SCAN is also known as ________

1) Circular scan 2) Cylindrical scan 3) Constant scan 4) None Answer: 1

In priority scheduling (CPU scheduling) Process Burst time Priority Arrival time P1 10 3 0