// Class Example and Exercise.
#include <iostream>
#include <cstdlib>// to define NULL

using namespace std;

class S{ // another dumb singly linked list class
// here the pointers point back to earlier items.
// Te effect is rather like a S????.

public:
	S(char c, S* p){chr=c; prev=p;} // must state 
	char chr;
	S* prev;  // pointer to previous item.
};// class S
main()
{
	S* t; // t is for top or perhaps tail!

     // put things onto the list
	t = new S('a', NULL);
	t = new S('b', t);
	t = new S('c', t);
	t = new S('d', t);

     // printout what is in the list
	cout << t->chr
	     <<	t->prev->chr
	     <<	t->prev->prev->chr
	     <<	t->prev->prev->prev->chr << endl;
   return 0;
}