title: How much of the "Objective-C" I'm learning is universal Objective-C, and not Apple's frameworks?
body: <p>This question is related to one of my others about C: <a href="https://stackoverflow.com/questions/2572988/what-can-you-do-in-c-without-std-includes-are-they-part-of-c-or-just-librar">What can you do in C without “std” includes? Are they part of “C,” or just libraries?</a></p>
  
  <p>I've become curious lately as to what is really contained the the core Objective-C language, and what parts of the Objective-C I've done for iPhone/OS X  development is specific to Apple platforms. </p>
  
  <p>I know that things like syntax are the same, but for instance, is <code>NSObject</code> and its torrent of <code>NS</code>-subclasses actually part of "standard" Objective-C? Could I use them in, say, Windows?</p>
  
  <p>What parts are universal for the most part, and what parts would I only find on an Apple platform?</p>
  
  <p>If you want, giving an example of Objective-C used elsewhere as an example of what is more "universal" would help me as well.</p>
  
  <p>Thanks! =)</p>