Question

Implement a First Come First Serve (FCFS) non-preemptive OS scheduling simulation with multiple processes, in python or c++.

The simulation takes the 3 processes(listed below) and they all arrive at time 0.

A single process consists of {CPU BURST, I/O BURST, CPU BURST, I/O BURST, etc…}

The simulation accounts for all 3 processes, and does not run one process at a time.

Process1 {4,24,5,73,3,31,5,27,4,33,6,43,4,64,5,19,2}

Process2 {18,31,19,35,11,42,18,43,19,47,18,43,17,51,19,32,10}

Process3 {6,18,4,21,7,19,4,16,5,29,7,21,8,22,6,24,5}

For example at time 0, Process1 arrives and enters running state, Process2 and Process3 are in the ready queue. After 4 time units Process1 completes its first CPU burst and goes to complete its 24 time unit I/O burst. Now Process2 will start its CPU burst for 18 time units at time 4, etc....

(1) Find the total waiting time for each of the processes.

(2) Find the total execution time for each of the processes.

The next process in ready queue will execute CPU burst after the previous process is sent to complete I/O burst.

After a process’s I/O burst time has elapsed, the process is sent to the ready queue.

Waiting time is defined as time spent in the ready queue.

Answer 1

#include<iostream>
using namespace std;

void waitingTime(int x[], int c,
                       int burst_time[], int wait_time[])
{
    wait_time[0] = 0;
    for (int m = 1; m < c ; m++ )
       wait_time[m] = burst_time[m-1] + wait_time[m-1] ;
}

void turnAroundTime( int x[], int c,
               int burst_time[], int wait_time[], int t[])
{
   for (int m = 0; m < c ; m++)
       t[m] = burst_time[m] + wait_time[m];
}

void avgTime( int x[], int c, int burst_time[])
{
   int wait_time[c], t[c], total_wt = 0, total_t = 0;

   waitingTime(x, c, burst_time, wait_time);
   turnAroundTime(x, c, burst_time, wait_time, t);

   cout << "x "<< "Burst time"
       << "Waiting time" << " Turn around time\c";

   for (int m=0; m<c; m++)
   {
       total_wt = total_wt + wait_time[m];
       total_t = total_t + t[m];
       cout << " " << m+1 << "\t\t" << burst_time[m] <<"\t "
           << wait_time[m] <<"\t\t " << t[m] <<endl;
   }

   cout << "Average waiting time = "
       << (float)total_wt / (float)c;
   cout << "\nAverage turn around time = "
       << (float)total_t / (float)c;
}

int main()
{
   int x[] = { 1, 2, 3};
   int c = sizeof x / sizeof x[0];

   int burst_time[] = {4,7,11};

   avgTime(x, c, burst_time);
   return 0;
}