a) The system menu will contain Ctrl-F4 to close a child window (as
opposed to the parent window), and Ctrl-F6 to move to the next MDI child.
b) As additional children are added to a frame these windows are
offset with respect to the origin to make all windows visible. This offset is
not reset to zero when all the children in a frame are closed.
c) If the standard call-back function 'CASCADE' is invoked from a
window containing a MDI frame, this will cascade the child windows with the
active window left at the top.