25. Consider the following snapshot of a system Calculate AWT&ATAT using SRTF Pre-emptive…

Step-by-step solution

1. 1. Gantt Chart (0-1)

   Time 0: P1 arrives • P1 starts execution • Runs for 1 unit

2. 2. Gantt Chart (1-2)

   Time 1: P2 arrives • P1 remaining: 7 • P2 burst: 4

3. 3. Gantt Chart (2-3)

   Time 2: P3 arrives • P2 remaining: 3 • P3 burst: 9

4. 4. Gantt Chart (3-7)

   Time 3: P4 arrives • P2 remaining: 2 • P4 burst: 5

5. 5. Gantt Chart (7-30)

   P4 (5) runs, completes at 12 • P1 (7) runs, completes at 19 • P3 (9) runs, completes at 28

6. 6. Calculate Times

   Completion Time (CT) • Turnaround Time (TAT) • Waiting Time (WT)

   $$\text{TAT} = \text{CT} - \text{AT}, \text{WT} = \text{TAT} - \text{BT}$$

7. 7. Average Times

   Sum all WT, TAT • Divide by N=4

   $$\text{AWT} = \frac{26}{4} = 6.5, \text{ATAT} = \frac{51}{4} = 12.75$$

8. 8. Yaad rakho / Key takeaway

   SRTF minimizes average waiting time by pre-empting processes.