// SJF Scheduling Simulated using C. Code by Nived Kannada
#include<stdio.h>
void main()
{
int n, bt[20], at[20],p[20],wt[20],tat[20],i,j , total=0, pos, temp;
float avgwt=0, avgtat=0;
//Reading number of processes from input.
printf("Enter number of processes: ");
scanf("%d",&n);
//Reading all burst times of processes from input. Assuming Arrival time is 0 for all.
printf("Enter burst time of each process: \n");
for(i=0;i<n;i++)
{
p[i]=i;
printf("Burst Time of P[%d]: ",i);
scanf("%d",&bt[i]);
at[i]=0; //Assuming AT is zero for all.
}
//Sorting Burst Time in its Ascending Order
for(i=0;i<n;i++)
{
pos = i;
for(j=i+1;j<n;j++)
{
if(bt[j]<bt[pos])
{
pos=j;
}
}
temp=bt[i];
bt[i]=bt[pos];
bt[pos]=temp;
//Also sorting corresponding PID values.
temp=p[i];
p[i]=p[pos];
p[pos]=temp;
}
//After this sorting step, the array bt[] is in ascending order. So the first element in the bt[] array doesn't have to wait. Its wt is now 0
/* CALCULATING WAITING TIME */
wt[0]=0; //The current first Process doesnt have to wait, (after sorting)
//Setting wt values for all other processes.
for(i=1;i<n;i++) //wt of 0 is set as 0. So we start with index 1 of wt[].
{
wt[i]=0; //initialize wt of i'th index as 0
for(j=0;j<i;j++)
{
wt[i] = wt[i] + bt[j]; // adding waiting times of previous processes and the current burst time.
}
}
/* CALCULATING TURNAROUND TIME */
for(i=0;i<n;i++)
{
tat[i] = wt[i] + bt[i]; //Equation for TAT is TAT= WT+BT
}
//Displaying Table
printf("\n\tPID\tAT\tBT\tWT\tTAT\n");
for(i=0;i<n;i++)
{
printf("\t%d\t%d\t%d\t%d\t%d\n",p[i],at[i],bt[i],wt[i],tat[i]);
}
//Calculating Average Waiting time and Average Turnaround Time
for(i=0;i<n;i++)
{
avgwt = avgwt + wt[i];
avgtat = avgtat + tat[i];
}
avgwt = avgwt/n;
avgtat = avgtat/n;
//Displaying Average WT and Average TAT
printf("\nAverage WT = %f\n", avgwt);
printf("\nAverage TAT = %f\n", avgtat);
}
//END OF PROGRAM
