Syntax: WINDOW nx ny x y

   Divide the plotting area into nx*ny regions, and use the (x,y)th.
The division is dependent upon the current EXPAND, so make sure that
you have the same EXPAND for each of a set of WINDOW commands.  Note
that the syntax has changed from Mongo.

   If the number of boxes desired in x or y (nx and/or ny) is negative,
the boxes will be drawn touching in that direction.

   The windows are not reset upon changing devices - use WINDOW 1 1 1 1
if you want to do so.