MDI is stand for Multiple Document Interface which is the powerful concept which is used in Microsoft Windows programming interface for creating an application which are enables users to work with multiple documents at the same time. In MDI each document is in a separate space with its own controls for scrolling. The user can see and work with different documents such as a spreadsheet, a text document, or a drawing space by simply moving the cursor from one space to another. An MDI application is something like the Windows desktop interface since both include multiple viewing spaces. MDI applications can be used for working on one document while referring to another document, viewing different presentations of the same information, viewing multiple Web sites at the same time, and any task that requires multiple reference points and work areas at the same time.