title: What is the "interface" keyword in MSVC?
body: <p>I'm looking through the Windows 8.1 SDK and in UnknownBase.h I'm seeing things like</p>
  
  <pre><code>typedef interface IUnknown IUnknown;
  </code></pre>
  
  <p>I've never seen this <code>interface</code> keyword before. Note that this is very definitely a <code>.h</code> header, processed by <code>cl.exe</code>. It's not IDL file, and it's not processed by <code>midl.exe</code>.</p>
  
  <p>I found this online: <a href="http://msdn.microsoft.com/en-us/library/50h7kwtb.aspx">http://msdn.microsoft.com/en-us/library/50h7kwtb.aspx</a></p>
  
  <p>But <code>__interface</code> is not the same as <code>interface</code></p>
  
  <p>Can anyone clue me in here?</p>