Minimum Average Waiting Time

The assignment content discusses five scheduling algorithms: Gantt charts, FCFS (First-Come-First-Served), SJF (Shortest Job First), SRNT (Shortest Remaining Time Next), and ROUND ROBIN. The solution provides the turnaround time and waiting time for each process under each algorithm. Additionally, the average waiting time is calculated for each algorithm, with SRNT resulting in the minimum average waiting time of 2.

Ans a) Gantt charts
FCFS
SJF: same as above
SRNT:
ROUND ROBIN:

Ans b & c) Turnaround time and waiting time of each process for each scheduling
algorithm
Formulas:
Turnaround time is = completion time – arrival time
Waiting time = turnaround time – burst time
FCFS & SJF:
Process Turn Around Time Waiting Time
P1 10-0=10 10-10=0
P2 11-1=10 10-1=9
P3 13-2=11 11-2=9
P4 16-4=12 12-3=9
P5 20-8=12 12-4=8
35
SRNT:
Process Turn Around Time Waiting Time
P1 20-0=20 20-10=10
P2 2-1=1 1-1=0
P3 4-2=2 12-2=0
P4 7-4=3 3-3=0
P5 12-8=4 4-4=0
10

ROUND ROBIN:
Process Turn Around Time Waiting Time
P1 20-0=20 20-10=10
P2 2-1=1 1-1=0
P3 5-2=3 3-2=1
P4 11-4=7 7-3=4
P5 17-8=9 9-4=5
Total 20
Ans d)
Average waiting time for each scheduling algorithm:
average waiting time = sum of all process waiting time/ total number of processes
FCFS:
average waiting time = sum of all process waiting time/ total number of processes
= (0+9+9+9+8) / 5 = 35 / 5 = 7
SJF: average writing time is same as FCFS and that is 7.
SRNT:
Average waiting time = (10+0+0+0+0) /5 = 2
ROUND ROBIN:
Average waiting time = (10+0+1+4+5)/5 = 20/5 = 4.
As we can see the minimum average time is of SRNT algorithm. So SRNT algorithm results in
the minimum average waiting time and that is 2.