title: Why is return 0 optional?
body: <p>Why, if I write </p>
  
  <pre><code>int main() 
  { 
      //... 
  }
  </code></pre>
  
  <p>do I not need to write <code>return 0;</code> at the end of the <code>main</code> function? Does the compiler do it for me?</p>
  
  <p>I use GCC / C99.</p>