Question

What is the waiting time and Turnaround time of each process for each of the scheduling algorithms?

Job	Arrival Time	Burst(msec)	Priority
A	0	6	3 (Silver)
B	1	2	1 (Diamond)
C	3	5	3 (Silver)
D	5	3	4 (Bronze)
E	7	2	2 (Gold)

(a) First-Come-First-Served (FCFS) scheduling.

(b) Preemptive PRIORITY scheduling .

(c) Highest Response Ratio Next (HRRN) scheduling.

(d) Round Robin (RR) (quantum = 4) scheduling.

(e) Which of the foregoing scheduling policies provides the lowest waiting time for this set of jobs? What is the waiting time with this policy? (Show your work)

Answer 1

(a) First-Come-First-Served (FCFS) scheduling:

A

B

C

D

E

0 6 8 13 16 18

Waiting time = start time - arrival time

Process	Waiting time
A	0-0=0
B	6-1=5
C	8-3=5
D	13-5=8
E	16-7=9

Average wait time=(0+5+5+8+9)/5=5.4

Turnaround time =completion time -arrival time

process	Turnaround time
A	6-0=6
B	8-1=7
C	13-3=10
D	16-5=11
E	18-7=11

Avg turnaround time=(6+7+10+11+11)/5=9

(b) Preemptive PRIORITY scheduling :

A

B

B

A

A

E

A

C

D

0 1 2 3 5 7 9 10 15 18

Turnaround time=completion time -arrival time

waiting time= turnaround time -burst time

process	turnaround time	waiting time
A	10-0=10	10-6=4
B	3-1=2	2-2=0
C	15-3=12	12-5=7
D	18-5=13	13-3=10
E	9-7=2	2-2=0

AVG WAITING TIME=21/5=4.2

(c) Highest Response Ratio Next (HRRN) scheduling:

A

B

C

E

D

0 6 8 13 15 18

process	turnaroundtime	watiting time
A	6-0=6	6-6=0
B	8-1=7	7-2=5
C	13-3=10	10-5=5
D	18-5=13	13-3=10
E	15-7=8	8-2=6

AVG WAITING TIME=26/5=5.2

d)round robin(quantum=4)

A

B

C

D

E

A

C

0 4 6 10 13 15 17 18

Turnaround time=completion time -arrival time

waiting time= turnaround time -burst time

process	turnaround time	waiting time
A	17-0=10	10-6=4
B	6-1=5	5-2=3
C	18-3=15	15-5=10
D	13-5=8	8-3=5
E	15-7=8	8-2=6

AVG WAITING TIME=5.6

e)Preemptive priority scheduling has least waiting time among all the scheduling mentioned above preemptive priority got the least average waiting time.Policy is average waiting time . Average Waiting time for preemptive priority scheduling is 4.2