Question

Operating System Theory and Design

Write a program to simulate the operation of two of CPU scheduling methods. The program does the following: 1. Get the number of processes from the user. 2. Get the burst time of each process from the user 3. Assume that all processes arrive at "O" to the ready queue. 4. The program lets the user select one of the two methods to implement the o e oo implement the CPU scheduling. time. You can use any programming language you would like to use. 5. The program calculates the average waiting time and the average turnaround 6. The program shows scheduling time of the CPU by using Gant Chart or table.

Answer 1

#include<iostream>
using namespace std;
void findsjf (int processes[], int n, int bt[])
{
   int i, j;
for (i = 0; i < n-1; i++)     
{
     
   for (j = 0; j < n-i-1; j++)
   {
         
       if (bt[j] > bt[j+1])
       {
           int temp = bt[j];
   bt[j] = bt[j+1];
   bt[j+1] = temp;
       }
   }
}
int wait[n], trn_arnd_time[n], total_wt = 0, total_trn_arnd_time = 0;
wait[0] = 0;

  
   for (int i = 1; i < n ; i++ )
       wait[i] = bt[i-1] + wait[i-1] ;
      
       for (int i = 0; i < n ; i++)
       trn_arnd_time[i] = bt[i] + wait[i];

  
   cout << "Processes "<< " Burst time "<< " Waiting time " << " Turn around time\n";
       for (int i=0; i<n; i++)
   {
       total_wt = total_wt + wait[i];
       total_trn_arnd_time = total_trn_arnd_time + trn_arnd_time[i];
       cout << " " << i+1 << "\t\t" << bt[i] <<"\t "<< wait[i] <<"\t\t " << trn_arnd_time[i] <<endl;
   }

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

void findfcfs( int processes[], int n, int bt[])
{
   int wait[n], trn_arnd_time[n], total_wait = 0, total_trn_arnd_time = 0;

  
   wait[0] = 0;

  
   for (int i = 1; i < n ; i++ )
       wait[i] = bt[i-1] + wait[i-1] ;

  
   for (int i = 0; i < n ; i++)
       trn_arnd_time[i] = bt[i] + wait[i];

  
   cout << "Processes "<< " Burst time "<< " Waiting time " << " Turn around time\n";

  
   for (int i=0; i<n; i++)
   {
       total_wait = total_wait + wait[i];
       total_trn_arnd_time = total_trn_arnd_time + trn_arnd_time[i];
       cout << " " << i+1 << "\t\t" << bt[i] <<"\t "
           << wait[i] <<"\t\t " << trn_arnd_time[i] <<endl;
   }

   cout << "Average waiting time is = "<< (float)total_wait / (float)n;
   cout << "\nAverage turn around time is = "<< (float)total_trn_arnd_time / (float)n;
}

int main()
{
int n, choice ;
cout<<"enter the number of processes"<<endl;
   cin>> n;
   int processes[n] ;
     
   int burst_time[n];
   cout<<"enter the burst times"<<endl;
   for(int i = 0;i<n;i++)
   {
       cin>>burst_time[i];
   }
   for(int j = 0;j<n;j++)
   {
       processes[j]= j+1;
   }
   cout<<"Press 1 to choose FCFS and press 2 to choose SJF"<<endl;
   cin>>choice;
   switch(choice)
   {
       case 1 :
       findfcfs(processes, n, burst_time);
       break;
       case 2:
   findsjf(processes, n, burst_time);
   break;
   default:
   cout<<"choice is not correct";
   }

  
  
   return 0;
}