The message statement can be used for both output and input.  It has a complicated set of "features"
that are dependent upon the redirection state for both the unnamed input and unnamed output.  Named streams cannot be used with the
message statement since there is no syntax to pass the named stream as an input or output target.  But the unnamed streams are
deeply linked to the message statement, though the details are not clear from the documentation.  Complicating this is the fact
that the message statement is used on an implicit basis during error handling to display messages.  These error messages can be sent
to the terminal, a redirected output stream or both depending on the state of the client.  Interestingly enough, if these implicit
message statements occur during a UI statement that is being redirected to a named output stream destination, the message output
does not go to that destination but instead goes to the terminal (***confirm this***).
<br/>
<br/>

Standard message statement (output only):
<TABLE WIDTH="100%" BORDER="1" CELLPADDING="2" CELLSPACING="2">
   <TR VALIGN=TOP>
      <TD>
         <P><BR>
         </P>
      </TD>
      <TD>
         <P>Unnamed INPUT Stream is Redirected (and marked NO-ECHO)</P>
      </TD>
      <TD>
         <P>Unnamed INPUT Stream is Redirected (and marked ECHO)</P>
      </TD>
      <TD>
         <P>Interactive INPUT Mode (Unnamed INPUT is NOT Redirected)</P>
      </TD>
   </TR>
   <TR VALIGN=TOP>
      <TD>
         <P>Unnamed OUTPUT is Redirected</P>
      </TD>
      <TD>
         <P>redirected output only (not on the terminal)</P>
      </TD>
      <TD>
         <P>redirected output only (not on the terminal)</P>
      </TD>
      <TD>
         <P>output is sent to BOTH the redirected output destination AND to
         the terminal</P>
      </TD>
   </TR>
   <TR VALIGN=TOP>
      <TD>
         <P>Interactive OUTPUT Mode (Unnamed OUTPUT is NOT Redirected)</P>
      </TD>
      <TD>
         <P>terminal output only</P>
      </TD>
      <TD>
         <P>terminal output only</P>
      </TD>
      <TD>
         <P>terminal output only</P>
      </TD>
   </TR>
</TABLE>
<P><BR>Message statement with a SET or UPDATE (input and output):</P>
<TABLE WIDTH=100% BORDER=1 CELLPADDING=2 CELLSPACING=2>
   <TR VALIGN=TOP>
      <TD>
         <P><BR>
         </P>
      </TD>
      <TD>
         <P>Unnamed INPUT Stream is Redirected (and marked NO-ECHO)</P>
      </TD>
      <TD>
         <P>Unnamed INPUT Stream is Redirected (and marked ECHO)</P>
      </TD>
      <TD>
         <P>Interactive INPUT Mode (Unnamed INPUT is NOT Redirected)</P>
      </TD>
   </TR>
   <TR VALIGN=TOP>
      <TD>
         <P>Unnamed OUTPUT is Redirected</P>
      </TD>
      <TD>
         <P>input value is read from the redirected stream, NO output
         occurs to the stream***</P>
      </TD>
      <TD>
         <P>input value is read from the redirected stream, the message
         text and the read input value are output to the stream***</P>
      </TD>
      <TD>
         <P>switch to interactive mode for the input then the message text
         and the read input value are output to the stream*** 
         </P>
      </TD>
   </TR>
   <TR VALIGN=TOP>
      <TD>
         <P>Interactive OUTPUT Mode (Unnamed OUTPUT is NOT Redirected)</P>
      </TD>
      <TD>
         <P>input value is read from the redirected stream, NO output
         occurs to the terminal 
         </P>
      </TD>
      <TD>
         <P>input value is read from the redirected stream, NO output
         occurs to the terminal</P>
      </TD>
      <TD>
         <P>terminal input and output only</P>
      </TD>
   </TR>
</TABLE>
<P><BR>Note that the source of the redirected input stream makes a
difference in behavior:</P>
<TABLE WIDTH=100% BORDER=1 CELLPADDING=2 CELLSPACING=2>
   <TR VALIGN=TOP>
      <TD>
         <P><BR>
         </P>
      </TD>
      <TD>
         <P>Output Redirected via Unnamed Stream</P>
      </TD>
      <TD>
         <P>Output Redirected via Named Stream (only affects implicit
         message statement usage due to error messages)</P>
      </TD>
   </TR>
   <TR VALIGN=TOP>
      <TD>
         <P>Redirected input source is /dev/null</P>
      </TD>
      <TD>
         <P>NO output to the terminal***<BR>YES output to the stream</P>
      </TD>
      <TD>
         <P>YES output to the terminal<BR>NO output to the stream</P>
      </TD>
   </TR>
   <TR VALIGN=TOP>
      <TD>
         <P>Redirected input source is NOT /dev/null</P>
      </TD>
      <TD>
         <P>YES output to the terminal<BR>YES output to the stream</P>
      </TD>
      <TD>
         <P>YES output to the terminal<BR>NO output to the stream</P>
      </TD>
   </TR>
</TABLE>
<P><BR>The entries marked *** in the tables above are believed to be
incomplete or incorrect in P2J.</P>