void DeleteList ( struct node** headRef )    { 

   struct node* current = *headRef; // deref headRef to get the real  head
    struct node* next;
    while (current != NULL) { 

      next = current->next; // note the next pointer
       free(current); // delete the node
      current = next; // advance to the next node
   }
   *headRef = NULL; // Again, deref headRef to affect the real head back
    // in the caller.
}