GATE | GATE CS Mock 2018 | Set 2 | Question 46

Consider the set of processes with arrival time(in milliseconds), CPU burst time (in milliseconds), and priority(0 is the highest priority) shown below. None of the processes have I/O burst time.

The waiting time (in milliseconds) of process P1 using preemptive priority scheduling algorithm is ____.
(A) 26
(B) 49
(C) 38
(D) 29

Answer: (C)
Explanation: The gantt chart is using preemptive priority scheduling algorithm:

Waiting Time = Completion time – Arrival time – Burst Time

Therefore, waiting time of process P1 is = 49 – 0 – 11 = 38

So, option (C) is correct.
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