PROGRAM TO UNDERSTAND SJF SCHEDULING ALGORITHM
/*
* C Program to Implement SJF Scheduling
*/
#include<stdio.h>
int main()
{
int bt[20],p[20],wt[20],tat[20],i,j,n,total=0,totalT=0,pos,temp;
float avg_wt,avg_tat;
printf("Enter number of process:");
scanf("%d",&n);
printf("\nEnter Burst Time:\n");
for(i=0;i<n;i++)
{
printf("p%d:",i+1);
scanf("%d",&bt[i]);
p[i]=i+1;
}
//sorting of burst times
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;
temp=p[i];
p[i]=p[pos];
p[pos]=temp;
}
wt[0]=0;
//finding the waiting time of all the processes
for(i=1;i<n;i++)
{
wt[i]=0;
for(j=0;j<i;j++)
//individual WT by adding BT of all previous completed processes
wt[i]+=bt[j];
//total waiting time
total+=wt[i];
}
//average waiting time
avg_wt=(float)total/n;
printf("\nProcess\t Burst Time \tWaiting Time\tTurnaround Time");
for(i=0;i<n;i++)
{
//turnaround time of individual processes
tat[i]=bt[i]+wt[i];
//total turnaround time
totalT+=tat[i];
printf("\np%d\t\t %d\t\t %d\t\t\t%d",p[i],bt[i],wt[i],tat[i]);
}
//average turnaround time
avg_tat=(float)totalT/n;
printf("\n\nAverage Waiting Time=%f",avg_wt);
printf("\nAverage Turnaround Time=%f",avg_tat);
}
Output:
Enter number of process:4
Enter Burst Time:
p1:5
p2:4
p3:12
p4:7
Process Burst Time Waiting Time Turnaround Time
p2 4 0 4
p1 5 4 9
p4 7 9 16
p3 12 16 28
Average Waiting Time=7.250000
Average Turnaround Time=14.250000
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