ITPEC FE Morning April 2022 Question 17
ITPEC FE Morning April 2022 — Question 17 of 80
FCFS Scheduling — Waiting Time — calculate waiting time for each process under First-Come-First-Serve.
Given processes with arrival and burst times, simulate FCFS (no preemption, execute in arrival order):
| Process | Arrival | Burst | Start | Finish | Waiting |
|---|---|---|---|---|---|
| P1 | 0 | 3 | 0 | 3 | 0 |
| P2 | 2 | 5 | 3 | 8 | 1 |
| P3 | 4 | 7 | 8 | 15 | 4 |
| P4 | 5 | 2 | 15 | 17 | 10 |
Formulas:
- start = max(finish_of_previous, arrival)
- waiting = start − arrival
- Equivalently: waiting = (finish − arrival) − burst
Why not others:
- (b) (0,2,4,5) — incorrect waiting for P2 (should be 1, not 2)
- (c) (0,3,5,7) — ignores arrival times, calculates as if all arrive at 0
- (d) (0,3,8,15) — these are start times, not waiting times
Key rule: In FCFS, waiting = start − arrival. Don't confuse waiting time with start time or turnaround time.
AI-generated — may contain errors
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