On OS/2 or Windows, a class library (DLL) can contain the implementations for multiple classes, all of which should be created when the DLL is loaded. On OS/2, when loading a DLL, the SOM class manager determines the name of a DLL initialization function, and if the DLL exports a function of this name, the class manager invokes that function (whose purpose is to create the classes in the DLL). SOMInitModule is the default name for this DLL initialization function.
On Windows, the SOM class manager does not call this function. It must be called from the default Windows DLL initialization function, LibMain. This call is made indirectly through the SOM_ClassLibrary macro (see the Example).