The first part of the script defines the coordinate system which will be
subsequently used (see above). If the user has chosen to display a bounding box, title, axis
labels, and/or system information, then these commands are also executed in the script.
The remainder of the script consists primarily
of a series of identical PostScript commands of the form:
[red green blue setrgbcolor] x y size symbol
Here red, green, and blue are RGB color values (between 0 and 1) which
determine the color of the subsequent point. The bracketted expression is optional and is
written only when color PostScript is desired. The values x and y are the position of the
point (in the user's coordinate system). The string size is actually a PostScript
integer variable, whereas symbol is a call to a PostScript function
(defined in the prologue) which plots a symbol at (x,y) in the size specified by size.