Question

Five jobs arrive nearly simultaneously for processing and their estimated CPU cycles are, respectively: Job A = 2 ms, Job B = 12 ms, Job C = 15 ms, Job D = 7 ms, and Job E = 3 ms.
Using FCFS, in what order would they be processed? What is the total time required to process all five jobs? What is the average turnaround time for each of these five jobs?

Answer 1

This is an example with solution:

Five jobs arrive nearly simultaneously for processing and their estimated CPU cycles are, respectively: Job A = 12, Job B = 2, Job C = 15, Job D = 7, and Job E = 3 ms.

a. Using FCFS, and assuming the difference in arrival time is negligible, in what order would they be processed? What is the total time required to process all five jobs? What is the average turnaround time for all five jobs?

Answer: The order of processing for the given jobs = A->B->C->D->E.

Total time needed to process all the jobs = 12+2+15+7+3 = 39 ms.

Turn around time for job A = 12 ms.

Turn around time for job B = 15 ms.

Turn around time for job C = 30 ms.

Turn around time for job D = 37 ms.

Turn around time for job E = 40 ms.

Answer : Therefore, the average turnaround time = (12+15+30+37+40)/5 = 26.8 ms.