feelgood

Hey Guys,

I'm working on figuring out process waiting time for 4 different operating system scheduling time.

The 4 different types are First Come, First Served, Shortest Job First, Non-preemptive and Round Robin.

I have 5 different Process

P1 takes 10 brust and are priority 3
P2 takes 1 burst and are priority 1
P3 takes 2 burst and are priority 3
P4 takes 1 burst and are priority 4
P5 takes 5 burst and are priority 2

FCFS
----------10-11--13-14-----19

Average wait time = (10+11+13+14)/5 = 9.6 millisecond

SJF
-1-2--4-----9----------19

Average wait time = (1+2+4+9)/5 = 3.2 millisecond

Nonpreemptive
-1-----6--8----------18-19

Average wait time = (1+6+8+18)/5 = 6.8 millisecond

RoundRobin Quantum = 1
-1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18-19

I believe I've got the first 3 right. But Round Robin is somewhat more difficult to understand. I understand that each process are allocated to 1 time quantum of CPU. But what I can't understand is how to calculate the average waiting time. It's not the same as calculating the average wait time as the other 3 since once process #2 and 4 are completed, they're not part of the average waiting time formula anymore.

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