  400 CONTINUE
</PRE>
Next, we choose a window and viewport, and set up an array <CODE>TR</CODE>
containing the 6 constants in the transformation between array indices
and world coordinates. In this case, the transformation is simple,
as we want $x = <CODE>I</CODE>$, $y = <CODE>J</CODE>$:
<PRE>
      CALL PGENV(0.,50.,5.,45.,0,2)
      TR(1) = 0.0
      TR(2) = 1.0
      TR(3) = 0.0
      TR(4) = 0.0
      TR(5) = 0.0
      TR(6) = 1.0
</PRE>
Finally, we call <CODE>PGCONT</CODE>; actually, we call it twice,