Programa Factorial

Código:

#include <stdio.h>

long int factorial (int x)
{
 int i; long int fac = 1;
 for (i=2; i<=x; i=i+1) fac=fac*i;
return (fac);
 }

main ()
{
int a;
do { printf ("\n Introduce un numero: ");
 scanf ("%d", &a);
if (a>0)
printf ("El factorial es %ld", factorial (a)); }
while (a > 0);
 }