title: Why do all the C files written by my lecturer start with a single # on the first line?
body: <p>I'm going through some C course notes, and <em>every</em> C program source file begins with a single <code>#</code> on the first line of the program.</p>
  
  <p>Then there are blank lines, and following that other stuff followed by the <code>main</code> function.</p>
  
  <p>What is the reason for the <code>#</code>?</p>
  
  <p>(It's out of term now and I can't really ask the chap.)</p>
  
  <p>Here's an example:</p>
  
  <pre class="lang-c prettyprint-override"><code>#
  
  #include &lt;stdio.h&gt;
  int main() {
     printf("Hello, World!");
     return 0;
  }
  </code></pre>