Given the information below, calculate the average waiting time using fcfs scheduling.
process burst time arrival time
p1 24 0
p2 3 10
p3 3 3
p4 10 5

20.25ms

Explanation:

Given

Process - Burst Time - Arrival Time

P1 - 24 - 0

P2 - 3 - 10

P3- 3 - 3

P4 - 10 - 5

Using the burst time, we'll first create the Gantt chart for the above process.

The Gantt chart is as follows

P1P2P3P4

024273033

Hence, waiting time for P1 will be 0

P1 requires 24 ms for completion, hence waiting time for P2 will be 24 ms

Similarly, waiting time for process P3 will be execution time of P1 + execution time for P2, which will be (24 + 3) ms = 27 ms.

For process P4 it will be the sum of execution times of P1, P2 and P3, which is 30.

The average weight time is then calculated as follows:

(0 + 24 + 27 + 30)/4

= 81/4

= 20.25 ms

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