c语言itob函数

k&r习题3-5，机械工业那本中文答案不咋的，只给了处理10进制以下的参考，本答案摘自网上的那本英文习题解答

/* itob(n,s,b)
 * converts the integer n into a base b char
 */
void itob(int n, char s[], int b)
{
    static char digits[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    int i, sign;
    if ( b < 2 || b > 36 ) {
             fprintf(stderr, "EX3_5: Cannot support base %d\n", b);
                  exit(EXIT_FAILURE);
    }
    if ((sign = n) < 0)
             n = -n;
    i = 0;
    do {
             s[i++] = digits[n % b];
    } while ((n /= b) > 0);
    if (sign < 0)
             s[i++] = '-';
    s[i]='\0';
    reverse(s);

}