title: mapping tab key in vim
body: <p>I'm using Vim 7.4. I have mapped "Tab" key in normal mode to switch to insert mode.</p>
  
  <pre><code>nnoremap &lt;tab&gt; a
  </code></pre>
  
  <p>This works fine in .txt file but not in .cpp files. Why is that?</p>
  
  <p>Besides mapping, I also have clang_complete settings in my .vimrc file.</p>