Multiple Document Interchange (MDI) is an application style in which users can open multiple document windows (sheets) in a single window (the MDI frame window) and move among the sheets.  The sheets are usually of the same type and have common features or uses.  

An MDI frame window has three parts:  a frame, a client area, and sheets.

For information about an area, click options on the left.

Simple Frames

A simple MDI frame usually has a menu bar and a status area for displaying MicroHelp. The sheets that can be opened in the frame do not have menus and therefore inherit menus from the MDI frame. 

The menu typically has an item that list all open sheets and another item that the user can use to tile, cascade, or layer the open sheets.

Complex Frames

A more complex frame has a menu for each sheet that can be opened in the frame. It can also be customized with buttons, StaticText, and other window objects.

mdi_1

When you save an MDI frame window, PowerBuilder creates a control named mdi_1 to identify the client area of the frame.  You use mdi_1 to refer to the client area in scripts for events in the frame window.

Note:Although mdi_1 is not a reserved word, problems can result when you use it to name windows or controls in MDI applications.