RR2_cpu_scheduling.c~

//C implementation of Round Robin
// Scheduling Algorithm with different arrival times.

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include <stdbool.h>


void QueueUpdate(int queue[],int timer,int arrival[],int n, int maxProccessIndex){
	int zeroIndex;
	for(int i = 0; i < n; i++){
		if(queue[i] == 0){
			zeroIndex = i;
			break;
		}
	}
	queue[zeroIndex] = maxProccessIndex + 1;
}

void QueueMaintainence(int queue[], int n){
	for(int i = 0; (i < n-1) && (queue[i+1] != 0) ; i++){
		int temp = queue[i];
		queue[i] = queue[i+1];
		queue[i+1] = temp;
	}
}

void CheckNewArrival(int timer, int arrival[], int n, int maxProccessIndex,int queue[]){
	if(timer <= arrival[n-1]){
	bool  newArrival = false;
	for(int j = (maxProccessIndex+1); j < n; j++){
			if(arrival[j] <= timer){
			if(maxProccessIndex < j){
				maxProccessIndex = j;
				newArrival = true;
			}
		}
	}
	//adds the incoming process to the ready queue
	//(if any arrives)
	if(newArrival)
		QueueUpdate(queue,timer,arrival,n, maxProccessIndex);
	}
}

//Driver Code
int main(){
	int n,tq, timer = 0, maxProccessIndex = 0;
	float avgWait = 0, avgTT = 0;
	printf("\nEnter the time quantum : ");
	scanf("%d",&tq);
	printf("\nEnter the number of processes : ");
	scanf("%d",&n);
	int arrival[n], burst[n], wait[n], turn[n], queue[n], temp_burst[n];
	bool complete[n];

	printf("\nEnter the arrival time of the processes : ");
	for(int i = 0; i < n; i++)
	  scanf("%d",&arrival[i]);

        printf("\nEnter the burst time of the processes : ");
	for(int i = 0; i < n; i++){
	  scanf("%d",&burst[i]);
	  temp_burst[i] = burst[i];
	}

	for(int i = 0; i < n; i++){ //Initializing the queue and complete array
		complete[i] = false;
		queue[i] = 0;
	}
	while(timer < arrival[0]) //Incrementing Timer until the first process arrives
		timer++;
	queue[0] = 1;
	
	while(true){
		bool flag = true;
		for(int i = 0; i < n; i++){
			if(temp_burst[i] != 0){
				flag = false;
				break;
			}
		}
		if(flag)
			break;

		for(int i = 0; (i < n) && (queue[i] != 0); i++){
			int ctr = 0;
			while((ctr < tq) && (temp_burst[queue[0]-1] > 0)){
				temp_burst[queue[0]-1] -= 1;
				timer += 1;
				ctr++;

				//Checking and Updating the ready queue until all the processes arrive
				CheckNewArrival(timer, arrival, n, maxProccessIndex, queue);
			}
			//If a process is completed then store its exit time
			//and mark it as completed
			if((temp_burst[queue[0]-1] == 0) && (complete[queue[0]-1] == false)){
				//turn array currently stores the completion time
				turn[queue[0]-1] = timer;	
				complete[queue[0]-1] = true;
			}
			
			//checks whether or not CPU is idle
			bool idle = true;
			if(queue[n-1] == 0){
				for(int i = 0; i < n && queue[i] != 0; i++){
					if(complete[queue[i]-1] == false){
						idle = false;
					}
				}
			}
			else
				idle = false;

			if(idle){
				timer++;
				CheckNewArrival(timer, arrival, n, maxProccessIndex, queue);
			}
	
			//Maintaining the entries of processes
			//after each premption in the ready Queue
			QueueMaintainence(queue,n);
		}
	}

	for(int i = 0; i < n; i++){
		turn[i] = turn[i] - arrival[i];
		wait[i] = turn[i] - burst[i];
	}

	printf("\nProgram No.\tArrival Time\tBurst Time\tWait Time\tTurnAround\n");
	printf("Time\n");
		
	for(int i = 0; i < n; i++){
	  printf("%i",i+1);
	  printf("\t\t%i",arrival[i]);
	  printf("\t\t%i",burst[i]);
	  printf("\t\t %i",wait[i]);
	  printf("\t\t %i\n",turn[i]);
	}
	for(int i =0; i < n; i++){
		avgWait += wait[i];
		avgTT += turn[i];
	}
	printf("Average wait time : %f\n",(avgWait/n));
	printf("Average Turn Around Time : %f\n",(avgTT/n));

	return 0;
	
}