Question

0. 

   Assume you have four processes with the following attributes: Process Total CPU Time A L 10 Arrival Time 0 2 6 CPU Burst 5 1 3 1/0 Burst 4 3 2 B 5 12

1. This assignment requires you to create simulations for different scheduling algorithms commonly employed by operating systems to achieve multiprogramming. All problems in this assignment assume the following:

   • The simulations you will be creating are for a uniprocessor system (single CPU).

   • Processes in these simulations will require CPU bursts of one or more time units followed by I/O bursts of one or more time units. For simplicity’s sake, when more than one process is executing its I/O burst at the same time, we will assume that the I/O bursts are using separate resources on the system and are not competing; there is no need to simulate processes waiting in an I/O queue for these simulations.

   • Assume you have four processes with the following attributes: (attached in the photo)

   • Perform a scheduling simulation for these four processes in the manner we covered in class, using the following algorithms:

   • First Come, First Served (FCFS)

   • Round Robin with Time Slice = 1

   • Round Robin with Time Slice = 3

   • For each simulation, if multiple processes would be placed into the ready queue at the same time, give the highest priority to a newly arriving process; the next highest priority to a process completing its blocked wait time (if two are unblocked at the same time, prefer the one that waited the longest); and finally, the lowest priority to a process that has just finished its time slice.

     For each of the four simulations, you must submit the following items listed below:

   • A timeline of the simulation (you may draw these by hand and scan/photograph them, or create them electronically using your word processor or graphics program)

   • Calculate the turnaround time, queue waiting time, and response time for each process

   • Calculate the average turnaround time, average queue waiting time, and average response time among all processes

   • Calculate the percentage of idle time for the CPU overall

   • Calculate the number of context switches involved (including whole and half context

     switches)

     Finally, write a brief summary indicating which scheduling algorithm you think performed the best for this set of processes and give reasons supporting your opinion.

   • Shortest Job (CPU Burst Time) First (no pre-emption, as we covered in class)

Answer 1

FCFS-First Come First Serve

Process	Arrival Time(A.T)	Total CPU Time	Completion Time(C.T)	Turnaround Time(TAT)	Waiting Time(W.T)
A	0	10	10	10	0
B	2	5	15	13	8
C	6	12	27	21	9
D	11	8	35	24	16
Total			87	68	33

Gantt Chart

A

B

C

D

0--------------------10----------------------15-----------------------27-----------------------35

TAT=CT-AT

WT=TAT-Total CPU Time

Average Turnaround Time=Total Turnaround Time/No. of processes

: 68/4=17

Average Waiting Time= Total Waiting Time/No. of processes

: 33/4=8.25

Average Completion Time=Total Completion Time/No. of processes

: 87/4=21.75

Round Robin with time slice=3

Process	Arrival Time(A.T)	Total CPU Time	Completion Time(C.T)	Turnaround Time(TAT)	Waiting Time(W.T)
A	0	10	24	24	14
B	2	5	14	12	7
C	6	12	35	29	17
D	11	8	32	21	13
Total			105	86	51

Average Turnaround Time=Total Turnaround Time/No. of processes

: 86/4=21.5

Average Waiting Time= Total Waiting Time/No. of processes

: 51/4=12.75

Average Completion Time=Total Completion Time/No. of processes

: 105/4=25.4

Round Robin with time slice=1

Process	Arrival Time(A.T)	Total CPU Time	Completion Time(C.T)	Turnaround Time(TAT)	Waiting Time(W.T)
A	0	10	25	25	15
B	2	5	13	11	7
C	6	12	35	29	17
D	11	8	29	18	10
Total			102	83	49

Average Turnaround Time=Total Turnaround Time/No. of processes

: 83/4=20.75

Average Waiting Time= Total Waiting Time/No. of processes

: 49/4=12.25

Average Completion Time=Total Completion Time/No. of processes

: 102/4=25.5