# Operating System Questions and Answers – CPU Scheduling Algorithms-2

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This set of Operating System Questions and Answers for Freshers focuses on “CPU Scheduling Algorithms-2” and will also be useful for interview preparations for freshers.

1. Which is the most optimal scheduling algorithm?
a) FCFS – First come First served
b) SJF – Shortest Job First
c) RR – Round Robin
d) None of the mentioned

Explanation: None.

2. The real difficulty with SJF in short term scheduling is ____________
a) it is too good an algorithm
b) knowing the length of the next CPU request
c) it is too complex to understand
d) none of the mentioned

Explanation: None.

3. The FCFS algorithm is particularly troublesome for ____________
a) time sharing systems
b) multiprogramming systems
c) multiprocessor systems
d) operating systems

Explanation: In a time sharing system, each user needs to get a share of the CPU at regular intervals.
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4. Consider the following set of processes, the length of the CPU burst time given in milliseconds.

```   Process    Burst time
P1           6
P2           8
P3           7
P4           3```

Assuming the above process being scheduled with the SJF scheduling algorithm.
a) The waiting time for process P1 is 3ms
b) The waiting time for process P1 is 0ms
c) The waiting time for process P1 is 16ms
d) The waiting time for process P1 is 9ms

Explanation: None.

5. Preemptive Shortest Job First scheduling is sometimes called ____________
a) Fast SJF scheduling
b) EDF scheduling – Earliest Deadline First
c) HRRN scheduling – Highest Response Ratio Next
d) SRTN scheduling – Shortest Remaining Time Next

Explanation: None.

6. An SJF algorithm is simply a priority algorithm where the priority is ____________
a) the predicted next CPU burst
b) the inverse of the predicted next CPU burst
c) the current CPU burst
d) anything the user wants

Explanation: The larger the CPU burst, the lower the priority.

7. Choose one of the disadvantages of the priority scheduling algorithm?
a) it schedules in a very complex manner
b) its scheduling takes up a lot of time
c) it can lead to some low priority process waiting indefinitely for the CPU
d) none of the mentioned

Explanation: None.

8. What is ‘Aging’?
a) keeping track of cache contents
b) keeping track of what pages are currently residing in memory
c) keeping track of how many times a given page is referenced
d) increasing the priority of jobs to ensure termination in a finite time

Explanation: None.

9. A solution to the problem of indefinite blockage of low – priority processes is ____________
a) Starvation
b) Wait queue
d) Aging

Explanation: None.

10. Which of the following statements are true? (GATE 2010)

```i) Shortest remaining time first scheduling may cause starvation
ii) Preemptive scheduling may cause starvation
iii) Round robin is better than FCFS in terms of response time```

a) i only
b) i and iii only
c) ii and iii only
d) i, ii and iii

Explanation: None.

11. Which of the following scheduling algorithms gives minimum average waiting time?
a) FCFS
b) SJF
c) Round – robin
d) Priority