ing documents of that type.  Writing 
   such a library requires
   some UI work, VM file operations, and an understanding of 
   the actions which the Viewer library requests of VILFile libraries.</P>

<P>Each VILFile library must have at least four 
   entry points (exported routines); the Viewer library will call these 
   routines when it needs the VILFile library to carry out certain tasks:
   </P>

<OL>
<LI><STRONG>Open:</STRONG><BR>
    <EM>Purpose:</EM> The Viewer library needs the VILFile document 