ackward compatibility with earlier releases of
    OCaml.
</p><p>

    The meaning of format string type parameters is as follows:
</p><p>
</p><ul>
<li><code class="code"><span class="keywordsign">'</span>a</code> is the type of the parameters of the format for formatted output
      functions (<code class="code">printf</code>-style functions);
      <code class="code"><span class="keywordsign">'</span>a</code> is the type of the values read by the format for formatted input
      functions (<code class="co