Calculate the waiting times and average waiting time for processes P1, P2, P3 with burst times 4, 13, 12…

Question

Calculate the waiting times and average waiting time for processes P1, P2, P3 with burst times 4, 13, 12 using FCFS.

ScanSolve AI Tutor · Accepted Answer

Here's the calculation for the waiting times and average waiting time using the First Come First Served (FCFS) scheduling algorithm, based on the provided burst times.

Given Burst Times:

P1: 4
P2: 13
P3: 12

The waiting time for a process $i$ is calculated as the sum of the burst times of all processes that completed before it. The formula from your notes, $WT_i = (\sum_{j=1}^{i} BT_j) - BT_i$ , correctly represents this.

Calculate the waiting time for P1.
P1 is the first process, so it starts immediately.
$WT_1 = 0$
Using the formula:
$WT_1 = (BT_1) - BT_1 = 4 - 4 = 0$
Calculate the waiting time for P2.
P2 waits for P1 to complete.
$WT_2 = BT_1$
Using the formula:
$WT_2 = (BT_1 + BT_2) - BT_2$ $WT_2 = (4 + 13) - 13$ $WT_2 = 17 - 13$ $WT_2 = 4$
Your calculation for P2 incorrectly subtracted 4 instead of 13.
Calculate the waiting time for P3.
P3 waits for P1 and P2 to complete.
$WT_3 = BT_1 + BT_2$
Using the formula:
$WT_3 = (BT_1 + BT_2 + BT_3) - BT_3$ $WT_3 = (4 + 13 + 12) - 12$ $WT_3 = 29 - 12$ $WT_3 = 17$
Calculate the average waiting time.
The average waiting time is the sum of all waiting times divided by the number of processes.
$\text{Average Waiting Time} = \frac{WT_1 + WT_2 + WT_3}{3}$ $\text{Average Waiting Time} = \frac{0 + 4 + 17}{3}$ $\text{Average Waiting Time} = \frac{21}{3}$ $\text{Average Waiting Time} = \boxed{\text{7}}$

Calculate the waiting times and average waiting time for processes P1, P2, P3 with burst times 4, 13, 12 using FCFS.

Answer

Step-by-step solution

Calculate the waiting time for P1.

Calculate the waiting time for P2.

Calculate the waiting time for P3.

Calculate the average waiting time.

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