print a unsigned long int using putchar

problem : print an unsigned long integer using only putchar

solution : we'll have to break the number and print the individual digit, we can use % operation to get the digits

code :

void putlong(unsigned long n) {
  if (n < 10) {
    putchar(n + '0');
    return;
  }
  putlong(n / 10);
  putchar(n % 10 + '0');
}