Direct3D uses globally unique identifiers, or GUIDs, to identify parts of the interface. When you use the QueryInterface method to determine whether an object supports an interface, you identify the interface you're interested in by using its GUID.

To use GUIDs successfully in your application, you must either define INITGUID prior to all other include and define statements, or you must link to the Dxguid.lib library. You should define INITGUID in only one of your source modules.

Note that you use GUIDs differently depending on whether your application is written in C or C++. In C, you pass a pointer to the GUID (&IID_IDirect3D, for example), but in C++, you pass a reference to it (simply IID_IDirect3D).

Like all of DirectX, the Direct3D component uses globally unique identifiers, or GUIDs, to identify parts of the API. DirectX for Visual Basic uses Strings to represent GUIDS where they are required—for example, when your application creates a DirectDraw7 object by calling the DirectX7.DirectDrawCreate method.

For more information, see Using GUIDs.