MDI vs. SDI — What's the Difference?

MDI, or Multiple Document Interface, is a graphical user interface principle that allows a user to work with several documents in one parent window. This model often comes with a 'Window' menu, which can be used to switch between different child windows. In contrast, SDI, the Single Document Interface, ensures that each document or task occupies its own standalone window. SDI is more straightforward because each task is isolated, reducing the complexity of navigation.

However, MDI is more efficient for multitasking as multiple child windows can be managed under one parent window, streamlining work in applications where multiple documents or tasks need simultaneous attention. A clear illustration of MDI can be found in older versions of Microsoft Office, where multiple Word documents could be opened within one Word window. In contrast, modern applications, including most web browsers, use SDI, where every new document or webpage is opened in a new window or tab.