It see all the burst times of the processes which one is least that should be processed first.
Here Job 3 having less burst time of all process,so it is executed according to the Optimal non preemptive scheduling algorithm.
So system waits until '1' unit of time because Job 3 comes at A.T of 1.
After completion of J3 all processes are arrived and execute according least burst time .
Gantt Chart.
0 1 3 8 17(completion times).
jobs |
A.T |
B.T |
C.T |
TAT |
J1 |
0.0 |
9 |
17 |
17 |
J2 |
0.6 |
5 |
8 |
7.4 |
J3 |
1.0 |
2 |
3 |
2 |
AVERAGE TAT=17+7.4+2/3=8.8