os simulation code.cpp

// C++ implementation for Priority Scheduling with  
//Different Arrival Time priority scheduling 
/*1. sort the processes according to arrival time  
2. if arrival time is same the acc to priority 
3. apply fcfs 
*/
  
#include <bits/stdc++.h> 
  
using namespace std; 
  
#define totalprocess 5 
  
// Making a struct to hold the given input  
  
struct process 
{ 
int at,bt,pr,pno; 
}; 
  
process proc[50]; 
  
/* 
Writing comparator function to sort according to priority if  
arrival time is same  
*/
  
bool comp(process a,process b) 
{ 
if(a.at == b.at) 
{ 
return a.pr<b.pr; 
} 
else
{ 
    return a.at<b.at; 
} 
} 
  
// Using FCFS Algorithm to find Waiting time 
void get_wt_time(int wt[]) 
{ 
// declaring service array that stores cumulative burst time  
int service[50]; 
  
// Initilising initial elements of the arrays 
service[0]=0; 
wt[0]=0; 
  
  
for(int i=1;i<totalprocess;i++) 
{ 
service[i]=proc[i-1].bt+service[i-1]; 
  
wt[i]=service[i]-proc[i].at+1; 
  
// If waiting time is negative, change it into zero 
      
    if(wt[i]<0) 
    { 
    wt[i]=0; 
    } 
} 
  
} 
  
void get_tat_time(int tat[],int wt[]) 
{ 
// Filling turnaroundtime array 
  
for(int i=0;i<totalprocess;i++) 
{ 
    tat[i]=proc[i].bt+wt[i]; 
} 
      
} 
  
void findgc() 
{ 
//Declare waiting time and turnaround time array 
int wt[50],tat[50]; 
  
double wavg=0,tavg=0; 
  
// Function call to find waiting time array 
get_wt_time(wt); 
//Function call to find turnaround time 
get_tat_time(tat,wt); 
      
int stime[50],ctime[50]; 
stime[0]=1; 
ctime[0]=stime[0]+tat[0]; 
// calculating starting and ending time 
for(int i=1;i<totalprocess;i++) 
    { 
        stime[i]=ctime[i-1]; 
        ctime[i]=stime[i]+tat[i]-wt[i]; 
    } 
      
cout<<"Process_no\tStart_time\tComplete_time\tTurn_Around_Time\tWaiting_Time"<<endl; 
      
    // display the process details 
      
for(int i=0;i<totalprocess;i++) 
    { 
        wavg += wt[i]; 
        tavg += tat[i]; 
          
        cout<<proc[i].pno<<"\t\t"<< 
            stime[i]<<"\t\t"<<ctime[i]<<"\t\t"<< 
            tat[i]<<"\t\t\t"<<wt[i]<<endl; 
    } 
      
        // display the average waiting time 
        //and average turn around time 
      
    cout<<"Average waiting time is : "; 
    cout<<wavg/(float)totalprocess<<endl; 
    cout<<"average turnaround time : "; 
    cout<<tavg/(float)totalprocess<<endl; 
  
} 
  
int main() 
{ 
int arrivaltime[] = { 1, 2, 3, 4, 5 }; 
int bursttime[] = { 3, 5, 1, 7, 4 }; 
int priority[] = { 3, 4, 1, 7, 9}; 
      
for(int i=0;i<totalprocess;i++) 
{ 
    proc[i].at=arrivaltime[i]; 
    proc[i].bt=bursttime[i]; 
    proc[i].pr=priority[i]; 
    proc[i].pno=i+1; 
    }  
      
    //Using inbuilt sort function 
      
    sort(proc,proc+totalprocess,comp); 
      
    //Calling function findgc for finding Gantt Chart 
      
    findgc();  
  
    return 0; 
} 
  
// This code is contributed by Apurv Siwach.