ype">[character]</span></td>
</tr>
<tr>
<td valign="top" align="left"><tt>action&nbsp;&nbsp;&nbsp;</tt></td><td>   action to be performed: can be 'read' or 'write' <br>&nbsp;&nbsp;&nbsp;<span class="type">[character]</span></td>
</tr>
</table>
</dd>
<br>
<dt>
<b>OUTPUT</b>
</dt>
<dd>
<table border="0">
<tr>
<td valign="top" align="left"><tt>unit&nbsp;&nbsp;&nbsp;</tt></td><td>   unit number returned by this function <br>&nbsp;&nbsp;&nbsp;<span class="type">[integer]</span></td>
</tr>
</table>
</dd>
<br>
</d