- Suppose that we have a multiprogrammed computer in which each job has identical characteristics. In one computation period, T, for a job, half the time is spent in I/O and the other half in processor activity. Each job runs for a total of N periods. Assume that a simple round-robin scheduling scheme is used and that I/O operations can overlap with processor operation. We define the following quantities:
· Turnaround time = actual time to complete a job.
· Processor utilization = percentage of time that the processor is active (not waiting).
For large N, compute approximate values for these quantities for one, two, and four simultaneous jobs, assuming that the period T is distributed in each of the following ways:
a. I/O first half, processor second half [3]
i) 1 job, Turnaround time and Processor utilization
ii) 2 jobs, Turnaround time and Processor utilization
iii) 4 jobs, Turnaround time and Processor utilization
b. I/O first and fourth quarters, processor second and third quarters. [3]
i) 1 job, Turnaround time and Processor utilization
ii) 2 jobs, Turnaround time and Processor utilization
iii) 4 jobs, Turnaround time and Processor utilization

a. 1 job, Turnaround time and Processor utilization:
TAT = NT, CPU utilization = 50%.
ii) 2 jobs, Turnaround time and Processor utilization:
TAT = NT, CPU utilization = 100%.
iii) 4 jobs, Turnaround time and Processor utilization:
TAT = (2N – ۱)T, CPU utilization = 100%. 2NT for TAT is also acceptable.
b. I/O first and fourth quarters, processor second and third quarters.
i) 1 job, Turnaround time and Processor utilization:
۲ points for TAT and 1 for utilization. Same answer as part a for 1 job.
ii) 2 jobs, Turnaround time and Processor utilization:
Same answer as above for part a for 2 jobs.
iii) 4 jobs, Turnaround time and Processor utilization:
Same answer as above for part a for 4 jobs.