TD>
<PRE>
<font color="#82140F">
`double_a_particular_variable'
{ 
    .x. = {rpn .x. 2 *}
}
.x. = 10
double_a_particular_variable
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Code such as that presented above occurs in many applications.  (Turn
the multiplication into an addition, and change `<font color="#82140F"><code>.x.</code></font>' to
`<font color="#82140F"><code>..ymargin..</code></font>', and you'll start to see the core of an application
that draws multiple graph panels, one above another.)  However, 