Q. Presume that the following processes arrive for execution at the times indicated. Every process will run the listed amount of time. In responding the questions use non pre-emptive scheduling and base all decisions on the information you have at the time the decision must be made.

a. What is the average revolve time for these processes with the FCFS scheduling algorithm?

b. What is the average revolve time for these processes with the SJF scheduling algorithm?

c. The SJF algorithm is supposed to improve performance however notice that we chose to run process P1 at time 0 because we did not know that two shorter processes would arrive soon. Calculate what the average turnaround time will be if the CPU is left idle for the first unit and then SJF scheduling is used. Keep in mind that processes P1 and P2 are waiting during this idle time thus their waiting time may increase. This algorithm could be recognized as future-knowledge scheduling.

Answer:

a. 10.53

b. 9.53

c. 6.86

Keep in mind that turnaround time is finishing time minus arrival time so you have to subtract the arrival times to compute the turnaround times. FCFS is 11 if you overlook to subtract arrival time.