class   ScreenList  {   // keep a list of ScreenObjs
struct  Window  {
    ScreenObj * head;       // a private structure
    Window * next; };       // to make a linked list
    Window * head;              // start of list
    Window * current;       // so we can step through list
public:
    void add(ScreenObj &);      // add to the list
    void remove(ScreenObj &);   // remove a ScreenObj
    void reset() { current = head; } // go to beginning
    ScreenObj & GetNext();
                        // return the next one or zero at end
};

main()  {
    Message M; Reader R; Dialog D;
    Screenlist  List;
    List.add(M); List.add(R); List.add(D);
    List.reset();
    while( (ScreenObj & Win = List.GetNext()) != 0)
        Win.ReDraw();       // ReDraw the whole list
}