For the processes listed in the following table, which of the following…
2015
For the processes listed in the following table, which of the following scheduling schemes will give the lowest average turnaround time?
\(\small \begin{array}{|c|c|c|} \hline \textbf{Process} & \textbf{Arrival Time} & \textbf{Process Time}\\\hline \text{A} & 0 & 3 \\\hline \text{B} & 1 & 6 \\\hline \text{C} & 4 & 4 \\\hline \text{D} & 6 & 2 \\\hline \end{array}\)
- A.
First Come First Serve
- B.
Non-preemptive Shortest Job First
- C.
Shortest Remaining Time
- D.
Round Robin with Quantum value two
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Correct answer: C
Key insight: running the job with the least remaining time whenever the CPU is free minimizes waiting for short jobs and therefore reduces average turnaround time.
First Come First Serve — average turnaround = 7.25 (A=3, B=8, C=9, D=9).
Non-preemptive Shortest Job First — average turnaround = 6.75 (A=3, B=8, C=11, D=5).
Shortest Remaining Time (preemptive) — average turnaround = 6.25 (A=3, B=14, C=4, D=4).
Round Robin with quantum 2 — average turnaround = 8.25 (A=5, B=14, C=9, D=5).
Conclusion: Shortest Remaining Time (the preemptive shortest-remaining-time policy) yields the lowest average turnaround time (6.25) for the given arrivals and service times, so it is the correct scheduling choice.
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