also destroy the UI used to display the 
    document.</P>
</OL>

<P>Below, we'll see source code for a simple VILFile library  
   which carries out these duties.</P>

<H3>GP File</H3>

<P>Before discussing the VILFile library's procedural code, 
   it's worthwhile to note directives needed in the library's GP file.</P>

<UL>
<LI>You will need to link the <STRONG>viewer</STRONG> library.</LI>
<LI>The first four exported routines correspond to the four 
    routines which each VILFile library must support. 