active</span> : <code class="type">bool <a href="Stdlib.html#TYPEref">ref</a></code></pre><div class="info ">
<div class="info-desc">
<p>This reference is initially set to <code class="code"><span class="keyword">false</span></code> in standalone
   programs and to <code class="code"><span class="keyword">true</span></code> if the code is being executed under
   the interactive toplevel system <code class="code">ocaml</code>.</p>
</div>
</div>

<pre><span id="VALos_type"><span class="keyword">val</span> os_