title: How should I write my C++ to be prepared for C++ modules?
body: <p>There are already two compilers that support C++ modules:</p>
  
  <ul>
  <li>Clang: <a href="http://clang.llvm.org/docs/Modules.html" rel="noreferrer">http://clang.llvm.org/docs/Modules.html</a></li>
  <li>MS VS 2015: <a href="http://blogs.msdn.com/b/vcblog/archive/2015/12/03/c-modules-in-vs-2015-update-1.aspx" rel="noreferrer">http://blogs.msdn.com/b/vcblog/archive/2015/12/03/c-modules-in-vs-2015-update-1.aspx</a></li>
  </ul>
  
  <p>When starting a new project now, what should I pay attention to in order to be able to adopt the modules feature when it is eventually released in my compiler?</p>
  
  <p>Is it possible to use modules and still maintain compatibility with older compilers that do not support it?</p>