Operating-System/Priority_preemptive.cpp at main · Anniebhalla16/Operating-System · GitHub

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/* Name : Annie Bhalla
   Roll No. : 19HCS4009
   Course : BSC (H) Computer Science
   Semester : 3
   Subject : Operating System
   Title : Priority Scheudling Preemptive
*/

#include<iostream>
using namespace std;

struct PRIOR
{
	int id;
	int arrivalTime;
	int burstTime;
	int priority;
	int turnaroundTime;
	int finishTime;
	int waitingTime;
	int remaining_bt;
};

// to enter the details of all processes

void input(int len,PRIOR obj[])
 {
 		for(int i=0;i<len;i++)
	{
		cout<<"\n Enter Arrival Time and Burst Time and Priority of Process P "<<i+1<<" : "<<endl;
		cin>>obj[i].arrivalTime>>obj[i].burstTime>>obj[i].priority;
		obj[i].id=i;
		obj[i].remaining_bt = obj[i].burstTime;
	}
 }

// Displaying process no, arrival time , burst time , finishing time , TA , WT

 void display(int n, PRIOR process[])
 {
    	cout<<" Process No. "<<'\t'<<"Arrival Time"<<'\t'<<"Burst Time"<<'\t'<<"Priority"<<'\t'<<" Finishing Time"<<'\t'<<" Turn Around Time"<<'\t'<<"Waiting Time"<<endl;

    	for(int i=0;i<n;i++)
		{

		cout<<process[i].id<<'\t'<<'\t'<<process[i].arrivalTime<<'\t'<<'\t'<<'\t'<<process[i].burstTime<<'\t'<<'\t'<<process[i].priority<<'\t'<<'\t'<<process[i].finishTime<<'\t'<<'\t'<<process[i].turnaroundTime<<'\t'<<'\t'<<process[i].waitingTime<<endl;

		}
 }


 // scheduling algo

 void schedule(int nop, PRIOR p[])
 {
 	int completed=0, timer=0;
 	while(completed!=nop)
 	{
 		int max_pr=0;
 		int index=-1;
 		for(int i=0;i<nop;i++)
 		{
 			if(p[i].remaining_bt !=0 && p[i].arrivalTime<= timer)
		 		if(p[i].priority> max_pr)
		 		 {
		 		 	max_pr= p[i].priority;
		 		 	index= i;
				  }
				if(p[i].priority == max_pr)
				  if(p[i].arrivalTime < p[index].arrivalTime)
				  index=i;
		 }

		 if(index!=-1)
		 {
		 	p[index].remaining_bt--;
		 	timer++;
		 	if(p[index].remaining_bt==0)
		 	{
		 		completed++;
		 		p[index].finishTime= timer;
		 		p[index].turnaroundTime = p[index].finishTime - p[index].arrivalTime;
		 		p[index].waitingTime = p[index].turnaroundTime - p[index].burstTime;
			 }
		 }
		 else
		 timer++;
	 }
 }


 // driver code
 int main()
{
	int nop;                               // nop= number of processes
	PRIOR *process;
	cout<<"\n Enter the number of Processes : ";
	cin>>nop;
	process = new PRIOR[nop];

	input(nop,process);                      // calling input function to enter AT and BT and priority

	// Displaying AT and BT of processes

   	cout<<" Process No. "<<'\t'<<"Arrival Time"<<'\t'<<"Burst Time"<<'\t'<<"Priority"<<endl;
	for(int i=0;i<nop;i++)
	{
		cout<<process[i].id<<'\t'<<'\t'<<process[i].arrivalTime<<'\t'<<'\t'<<process[i].burstTime<<'\t'<<'\t'<<process[i].priority<<endl;
	}

	schedule(nop, process);     				// calling schedule function

	cout<<endl<<endl<<endl;
	float avg_waiting_time=0;

	for(int i=0;i<nop;i++)
	avg_waiting_time += process[i].waitingTime;

	avg_waiting_time= avg_waiting_time / nop;

	cout<<endl<<endl<<endl;
	cout<<" *******              Result                 ********"<<endl<<endl;
 	display(nop,process);

    cout<<endl<<endl;
	cout<<"\n Average waiting Time is : "<<avg_waiting_time<<" ms ";

	delete [] process;


	return 0;
}