Shortest_Job_First.c

// shortest job first scheduling algorithm

#include <stdio.h>

struct process
{
	int pid;
	int bt;
	int wt;
	int tat;
}p[50];

int main()
{
	// initialize variables
	int n,temp,i,j;
	
	printf("Please Enter no of processes : ");
	scanf("%d",&n);
	
	printf("\nPlease Enter Burst Time of processes : \n");
	for(i=0;i<n;i++)
	{
		printf("P%d : ",i+1);
		p[i].pid = i+1;
		scanf("%d",&p[i].bt);
	}
	
	// sort
	for(i=0;i<n;i++)
	{
		for(j=0;j<n-1;j++)
		{
				if(p[j].bt > p[j+1].bt)
				{
					temp = p[j].pid;
					p[j].pid = p[j+1].pid;
					p[j+1].pid = temp;
					
					temp = p[j].bt;
					p[j].bt = p[j+1].bt;
					p[j+1].bt = temp;					
				}
		}
	}
	
	// wt&tat
	for(i=0;i<n;i++)
	{
		if(i==0)
		{
			p[i].wt = 0;
			p[i].tat = p[i].wt + p[i].bt;
			continue;
		}
		
		p[i].wt = p[i-1].bt + p[i-1].wt;
		p[i].tat = p[i].wt + p[i].bt;
	}
	
	// print
	printf("\nPid\tBT\tWT\tTAT\n");
	for(i=0;i<n;i++)
	{
		printf("%d\t%d\t%d\t%d\n",p[i].pid,p[i].bt,p[i].wt,p[i].tat);
	}
	
	// Avg wt
	temp = 0;
	for(i=0;i<n;i++)
		temp += p[i].wt;	
	printf("\ntotal waiting time\t\t:%d\n", temp);
	printf("average waiting time\t\t:%f\n",(float)temp/n);
	
	// Avg tat
	temp = 0;
	for(i=0;i<n;i++)
		temp += p[i].tat;
	printf("total turn around time\t\t:%d\n",temp);
	printf("average turn around time\t:%f\n",(float)temp/n);
}