Quiz 4 Solutions

Below is a table of jobs that we must schedule on a batch operating system.

       JOB     RUN TIME
        J1      10 seconds
        J2       5 seconds
        J3       2 seconds
        J4       8 seconds

1. Create a time-line to illustrate the First-Come First-Served (FCFS) strategy. It should include the start/stop times of each job.

   

2. Compute the average turnaround time of the four jobs using your FCFS time-line from the previous question. (Turnaround time is the interval between arrival and completion, but since all these jobs are available at time zero, we can just use the completion time.)

   Add up the completion times: 10+15+17+25 = 67, and divide by 4 = 16.75.

3. Create a time-line to illustrate the Shortest Job First (SJF) strategy. It should include the start/stop times of each job.

   

4. Compute the average turnaround time of the four jobs using your SJF time-line from the previous question.

   Add up the completion times: 2+7+15+25 = 49, and divide by 4 = 12.25.