nter to user defined data that will be passed, as an argument,
to the function pointed to by <i>fn_ptr</i>. In C it may be NULL. In Fortran
it may be omitted.</td>
</tr>

<tr>
<td><b>Returned Value:</b></td>

<td></td>
</tr>

<tr>
<td VALIGN=TOP>&nbsp;&nbsp;&nbsp; int</td>

<td><a href="ug_interface.html#Error Codes">Error code</a>.</td>
</tr>

<tr>
<td><b>Example:</b></td>

<td></td>
</tr>

<tr NOSAVE>
<td VALIGN=TOP NOSAVE></td>

<td VALIGN=TOP NOSAVE>The interface function
<br>&nbsp;&nbsp;&nbsp; int <b>Z