#include<stdio.h>
#include<stdlib.h>
#include<math.h>
int main()
{
int num = 1;
char c = 'a';
float sum = 0, ssum = 0, f = 0;
char g[8];
int i = 0,j = 0;
printf("How many numbers to average?");
i = 0;
while( i < 7 && (c = getchar()) != '\n') {
g[i++] = c;
}
g[i]='\0';
num = atoi(g);
if(num <= 0) {
printf("Error must enter value > 1\nExiting...");
exit(1);
}
for(j = 0;j<num;++j) {
printf("Enter number %d of %d:",j+1,num);
i = 0;
while( i < 7 && (c = getchar()) != '\n') {
g[i++] = c;
}
g[i]='\0';
f = atof(g);
sum += f;
ssum += f*f;
}
printf("The standard deviation is %g",sqrt(ssum/num - pow(sum/num,2)));
getchar();
return 0;
}