sum digits of factorial with double in C

fc.c

/* sums the digits of the factorial 10 (since not much larger can be held by a double)
   copyright (c) 2011 darkf
   use for anything, CC-0 or public domain etc */

#include <stdio.h>
#include <string.h>
double f(int n){return !n?1:n*f(n-1);}
int g(char* b){int x=0,i;for(i=0;i<strlen(b);i++)x+=b[i]-'0';return x;}
main(){char b[256];double x=f(10);sprintf(b,"%.0f",x);printf("%d",g(b));}