Windows

    A window is an area of  the  screen  which  is  currently being used.
    It usually has  the  background  saved  so  that  when  it is removed
    what was behind it is still there.

    However, these  days  a  screen  can  use  over  1  Mb of information
    and saving the background  is  not  always  possible (or just a plain
    nuisance), especially under DOS.

    A window has buttons  associated  with  it.   That is, buttons in one
    window are not active while the user in playing in another window.

    Thus each window can have a  close  window  button (the button in the
    top corner which  closes  the  window)  but  one  can  only close the
    active window.

    I  strongly  recommmend  you  trace   through  the  example  file  to
    understand how the system works.