The completion order of the 3 processes under the policies FCFS and RR2 (round robin scheduling with CPU quantum of 2 time units) are

Question

Consider the 3 process, 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 I P₂, P₃ 

(B) FCFS: P₁, P₃, P₂ RR₂: P₁, P₃, P₂ 

(C) FCFS: P₁, P₂, P₃ RR₂: P₁, P₃, P₂ 

(D) FCFS: P₁ I P₃, P₂ RR₂: P₁, P₂, P₃

Answer 1

(C) FCFS: P₁, P₂, P₃ RR₂: P₁, P₃, P₂ 

The completion order for round robin is given below 

At time t = 2 

P₁ will move to ready queue, so status of ready queue will be:

P1

(↑ front)

At time t= 3. 

P₃ enters the system so it will be enqueued.

P3

P1

(↑ front)

At time t = 4, 

When quantum of P₂ is done. www.examrace.com We need to enqueue P₂ into ready queue & next process t o be executed which w ill be taken from front of Ready queue i.e, P₁, 

Ready queue :

P2

P3

(↑ front)

So using round robin scheduling, the completion order is P₁,P₃,P₂