Consider the 3 processes, P1, P2 and P3 shown in the table.
Process Arrival time Time Units Required P1 0 5 P2 1 7 P3 3 4
The completion order of the 3 processes under the policies FCFS and RR2 (round robin scheduling with CPU quantum of 2 time units) are
(A)
FCFS: P1, P2, P3 RR2: P1, P2, P3
(B)
FCFS: P1, P3, P2 RR2: P1, P3, P2
(C)
FCFS: P1, P2, P3 RR2: P1, P3, P2
(D)
FCFS: P1, P3, P2 RR2: P1, P2, P3
Answer: (C)
Explanation:
FCFS is clear. In RR, time slot is of 2 units. Processes are assigned in following order p1, p2, p1, p3, p2, p1, p3, p2, p2
This question involves the concept of ready queue. At t=2, p2 starts and p1 is sent to the ready queue and at t=3 p3 arrives so then the job p3 is queued in ready queue after p1. So at t=4, again p1 is executed then p3 is executed for first time at t=6.
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