PRESET Statement Details
 
Syntax
  PRESET [STEP](x,y)[,color]
 
PRESET works exactly like PSET, except that if the color is not specified,
the background color is selected.
 
  Argument      Description
  STEP          Indicates that the given x and y coordinates are
                relative, not absolute. The coordinates are treated as
                distances from the most recent cursor location, not
                distances from the (0,0) screen coordinate.
 
                For example, if the most recent point referenced were
                (10,10),
                  PRESET STEP (10,5)
                would reference the point at (20,15).
 
  xcoordinate   The x coordinate of the pixel that is to be set.
  ycoordinate   The y coordinate of the pixel that is to be set.
  color         The color attribute for the specified point.
 
If a coordinate is outside the current viewport, no action is taken,
nor is an error message given.