In this section:
%fr (MDI Frame) is used in a parent window to define a frame into which child windows are placed. These windows can be moved and re-sized within this MDI (multi-document interface) frame. The format takes two integer arguments that define the width and height of the frame in pixels. A MDI frame can be preceded by the pivot (%pv (Pivot)), in which case it will expand as the window expands. There is an example using %fr appears with %aw.
A grave accent (`) can be added to %fr (MDI Frame) to cause it to maintain a handle identifying the currently selected child window. An extra integer (kind=7) argument is supplied to hold the returned handle. The integer will be zero if there is no child window. When a child window is created, the handle is obtained by using %hw (see Window handle - %hw). A comparison may then be made between the handle updated by %fr and those previously returned by %hw.