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# Develop a Gantt Chart, Average Waiting time, FCFS, SJF, RR

RGPV 2020 CPU Scheduling Algorithm

Consider the following set of processes.

 Process Burst Time Arrival Time P1 3 0 P2 5 1 P3 2 2 P4 5 3 P5 5 4

Develop a Gantt-chart and calculate the average waiting time using:
i) FCFS
ii) SJF
iii) Round Robin (q = 1)
Solution:

i) FCFS
 Gantt Chart for FCFS

From above Gantt Chart waiting time for each process:
Waiting time = Turnaround time – Burst time

 Process Waiting time P1 3-3=0 P2 7-5=2 P3 8-2=6 P4 12-5=7 P5 16-5=11

Average waiting time = Sum of waiting time / Number of processes
Average waiting time = (0+2+6+7+11)/5 = 5.2
ii) SJF
 Gantt Chart SJF

From above Gantt Chart waiting time for each process:
Waiting time = Turnaround time – Burst time
 Process Waiting time P1 3-3=0 P2 9-5=4 P3 3-2=1 P4 12-5=7 P5 16-5=11
Average waiting time = Sum of waiting time / Number of processes
Average waiting time = (0+4+1+7+11)/5 = 4.6
iii) Round Robin (q = 1)
 Gantt Chart RR

From above Gantt Chart waiting time for each process:
Waiting time = Turnaround time – Burst time
 Process Waiting time P1 11-3=8 P2 17-5=12 P3 6-2=4 P4 16-5=11 P5 16-5=11
Average waiting time = Sum of waiting time / Number of processes
Average waiting time = (8+12+4+11+11)/5 = 9.2