What does a pipe in a macro signify?
<p>How is the following macro definition resolved?</p>

<pre><code>#define EMAIL_SERVER_ADAPTER_FATAL_ERROR     MSB_RETURN_TYPE_FATAL_ERROR | 1
</code></pre>

<p>I mean, is it resolved to 1 or to MSB_RETURN_TYPE_FATAL_ERROR and why?</p>
