Question

6. Consider the following set of processes P1, P2, P3, P4.
Process Burst Time Arrival Time Priority
P1 3 0 1
P2 5 1 2
P3 8 3 3
P4 4 4 2
a) Draw Gantt charts that illustrate the execution of these processes using the following scheduling algorithms: first-come, first-served (FCFS), priority scheduling (larger number=high priority), and Round-Bobin (RR, quantum=2).
b) Compute the average waiting time, turnaround time for the three algorithms. Turnaround time – amount of time to execute a process (the time from submission to completion). Waiting time – amount of time a process has been waiting in the ready queue.

*Please answer in text format, not hand written*

Answer 1

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b)

TAT=CT-AT and WT=TAT-BT

FCFS

Process	AT	BT	CT	TAT	WT
P1	0	3	3	3	0
P2	1	5	8	7	2
P3	3	8	16	13	5
P4	4	4	20	16	12

   Average TAT= (3+7+13+16)/4=39/4=9.75

   Average WT=    (0+2+5+12)/4= 19/4=4.75

Priority Scheduling

Process	AT	BT	CT	TAT	WT
P1	0	3	3	3	0
P2	1	5	16	15	10
P3	3	8	11	8	0
P4	4	4	20	16	12

   Average TAT=   (3+15+8+16)/4=10.5

   Average WT=   (0+10+0+12)/4=5.5

Round Robin Scheduling

Average TAT= (5+15+17+11)/4=48/4=12

Average WT= (2+10+9+7)/4=28/4=7

Process	AT	BT	CT	TAT	WT
P1	0	3	5	5	2
P2	1	5	16	15	10
P3	3	8	20	17	9
P4	4	4	15	11	7