Understanding The COM Single-Threaded Apartment Part 1

// SimpleCOMObject1.idl : IDL source for SimpleCOMObject1.dll
//

// This file will be processed by the MIDL tool to
// produce the type library (SimpleCOMObject1.tlb) and marshalling code.

import "oaidl.idl";
import "ocidl.idl";
	[
		object,
		uuid(96A34C8B-E166-41EB-A390-9F9845F40D9F),
		dual,
		helpstring("ISimpleCOMObject1 Interface"),
		pointer_default(unique)
	]
	interface ISimpleCOMObject1 : IDispatch
	{
		[id(1), helpstring("method Initialize")] HRESULT Initialize();
		[id(2), helpstring("method Uninitialize")] HRESULT Uninitialize();
		[id(3), helpstring("method DoLengthyFunction")] HRESULT DoLengthyFunction([in] long lTimeout);
	};

[
	uuid(5F12C0E4-FB47-4FAF-8EAF-5C733637698E),
	version(1.0),
	helpstring("SimpleCOMObject1 1.0 Type Library")
]
library SIMPLECOMOBJECT1Lib
{
	importlib("stdole32.tlb");
	importlib("stdole2.tlb");

	[
		uuid(8B88E59A-4BB7-4DBC-819A-2E682845A4AE),
		helpstring("_ISimpleCOMObject1Events Interface")
	]
	dispinterface _ISimpleCOMObject1Events
	{
		properties:
		methods:
		[id(1), helpstring("method LengthyFunctionCompleted")] HRESULT LengthyFunctionCompleted([in] long lStatus);
	};

	[
		uuid(11EF2E3F-9887-4530-8EE0-D8A57D69653A),
		helpstring("SimpleCOMObject1 Class")
	]
	coclass SimpleCOMObject1
	{
		[default] interface ISimpleCOMObject1;
		[default, source] dispinterface _ISimpleCOMObject1Events;
	};
};