double sum,ave,var,std;
double data[]={1,2,3,4,5,6,7,8,9};
int n = (int)(sizeof(data) / sizeof(data[0]));
int i;

sum=0.0;
for(i=0;i<n;i++){
sum+=data[i];
}
ave = sum / n;

var=0.0;
for(i=0;i<n;i++){
var += pow( (data[i] - ave) , 2 );
}
var / = (n-1);

std = sqrt(var);