void LinkedListInsert(ptrType& HeadPtr, 
                      itemType NewItem, bool& Success)
{
   if ((HeadPtr == NULL) || (NewItem < HeadPtr->Item))
   {  // base case: insert NewItem at beginning
      // of the linked list to which HeadPtr points
      ptrType NewPtr = new node;
      Success = bool(NewPtr != NULL);
      if (Success)
      {  NewPtr->Item = NewItem;
         NewPtr->Next = HeadPtr;
         HeadPtr = NewPtr;
      }  // end if 
   }

   else 
      LinkedListInsert(HeadPtr->Next,     NewItem,    Success);
}  // end LinkedListInsert