Building an MDI frame window
When you create a new window in PowerBuilder, its default window
type is Main. Select mdi! or mdihelp! on the General property page
to change the window to an MDI frame window.
When you change the window type to MDI, you must associate
a menu with the frame. Menus usually provide a way to open sheets
in the frame and to close the frame if the user has closed all the
About menus and sheets A sheet can have its own menu but is not required to. When
a sheet without a menu is opened, it uses the frame’s menu.