void displayForward()
 {
   Link* pCurrent = pFirst;
   while(pCurrent != NULL)
   {
     pCurrent->displayLink();
     pCurrent = pCurrent->pNext;
   }
   cout << endl;
 } // end displayForward()
 void displayBackward()
 {
   Link* pCurrent = pLast;
   while(pCurrent != NULL)
   {
     pCurrent->displayLink();
     pCurrent = pCurrent->pPrevious;
   }
   cout << endl;
 } // end displayBackward()
	void displayList()
	{
		cout << "List (first-->last): ";
		Link* pCurrent = pFirst;
		while(pCurrent != NULL)
		{
			pCurrent->displayLink();
			pCurrent = pCurrent->pNext;
		}
		cout << endl;
	}
    void displayList()
    {
	Link* pCurrent = pFirst;
	cout << "Sorted List (first-->last): ";
	while(pCurrent != NULL)
	{
	    pCurrent->displayLink();
	    pCurrent = pCurrent->pNext;
	}
	cout << endl;
    } // end displayList()