GATE|GATE-CS-2011

 

GATE|GATE-CS-2011|Question 65

Consider the following table of arrival time and burst time for three processes P0,P1,P2. 

Process	Arrival Time	Burst Time
P0	0ms	9ms
P1	1ms	4ms
P2	2ms	9ms

The pre-emptive shortest job first algorithm is used.Scheduling is carried out only at arrival or completion of processes.What is the average waiting time for the three processes? 

(A)5.0ms.

(B)4.33ms.

(C) 6.33ms.

(D)7.33 ms.

Answer: (A)

P0

P1

P0

P2

0               1                            5               13         22

Average waiting time

=W1+w2+w3/3

=(5-1)+0+(13-2)/3

=5.0ms

S0 option (A) is correct 5.0ms.