The QMF for Windows API is accessed by creating an instance of the QMF for Windows API object. The object is available in two different variations which are functionally equivalent, but have a significant difference in implementation.
The multiple-use object is named QMFWin.InterfaceMU. For compatibility with previous versions of QMF for Windows, the name QMFWin.Interface is also defined as an alias for QMFWin.InterfaceMU. When you create multiple instances of the multiple-use object, they are all handled by a single instance of the QMF for Windows application.
The single-use object is named QMFWin.InterfaceSU. When you create multiple instances of the single-use object, they are each handled by a separate instance of the QMF for Windows application. Using the multiple-use object is generally more efficient than using the single-use object, as it requires running only one instance of the QMF for Windows application. There is a signicant restriction with the multiple-use object, which is that if multiple objects are used to establish connections to the same server, each connection must use the same user ID and password. This restriction does not exist with the single-use object.
The single-use object has one restriction that the multiple-use object does not. When calling the CopyQMFObject() or SaveDataEx() functions, the Server parameter must be NULL.
QMFWin.InterfaceMU.7 and QMFWin.InterfaceSU.7 are aliases of QMFWin.InterfaceMU and QMFWin.InterfaceSU, respectively, and are used to specifically identify the objects implemented by QMF for Windows Version 7. You should use the version-specific names only if you want to ensure that your application will continue to use the Version 7 objects, even after installing a later version of QMF for Windows. In this case, your application will no longer run if you replace your QMF for Windows Version 7 installation with a later version.