The CANCEL WINDOW command cancels the specified screen window
    definitions. After a window definition has been canceled, that
    window name can no longer be used on DISPLAY or SET DISPLAY
    commands. Only the definition of the window name is deleted;
    the actual screen region specified by the window name is not
    affected. Screen displays that were declared with the window
    name are not affected except that the SHOW DISPLAY command shows
    numeric window coordinates instead of the canceled window name.