#include <stdio.h>

#include <stdlib.h>

#include <string.h>

int fac(int n)

{

if (n < 2) return(1); /* 0! == 1! == 1 */

return (n)*fac(n-1); /* n! == n*(n-1)! */

}

char *reverse(char *s)

{

register char t, /* tmp */

*p = s, /* fwd */

*q = (s + (strlen(s) - 1)); /* bwd */

while (p < q) /* if p < q */

{

t = *p; /* swap & move ptrs */

*p++ = *q;

*q-- = t;

}

return(s);

}

int main()

{

char s[BUFSIZ];

printf("4! == %d\n", fac(4));

printf("8! == %d\n", fac(8));

printf("12! == %d\n", fac(12));

strcpy(s, "abcdef");

printf("reversing 'abcdef', we get '%s'\n", \

reverse(s));

strcpy(s, "madam");

printf("reversing 'madam', we get '%s'\n", \

reverse(s));

return 0;

}