IBPS IT SO-Operating system-CPU Scheduling Algorithms-2

CPU Scheduling Algorithms-2

1) The most optimal scheduling algorithm is :
a) FCFS – First come First served
b) SJF – Shortest Job First
c) RR – Round Robin
d) None of these

Answer: b
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 these

Answer: b
Explanation: None.

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

Answer: b
Explanation: In a time sharing system, each user needs to get a share of the CPU at regular intervals.

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

i) 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.

Answer: a
Explanation: None.

ii) Assuming the above process being scheduled with the SJF scheduling algorithm :
a) The waiting time for process P2 is 3ms.
b) The waiting time for process P2 is 0ms.
c) The waiting time for process P2 is 16ms.
d) The waiting time for process P2 is 9ms.

Answer: c
Explanation: None.

iii) Assuming the above process being scheduled with the SJF scheduling algorithm :
a) The waiting time for process P4 is 3ms.
b) The waiting time for process P4 is 0ms.
c) The waiting time for process P4 is 16ms.
d) The waiting time for process P4 is 9ms.

iv) Assuming the above process being scheduled with the SJF scheduling algorithm :
a) The waiting time for process P3 is 3ms.
b) The waiting time for process P3 is 0ms.
c) The waiting time for process P3 is 16ms.
d) The waiting time for process P3 is 9ms.

Answer: d
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

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

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

7) One of the disadvantages of the priority scheduling algorithm is that :
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 these

Answer: c
Explanation: None.

8) ‘Aging’ is :
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

Answer: d
Explanation: None.

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

Answer: d
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 terns of response time

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

Answer: d
Explanation: None.

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

Answer: b
Explanation: None.