The SM (2.3.1) graphics package written by Robert Lupton and Patricia Monger is extensively used to produce graphical output and hardcopy. It is often used in its interpreter mode for two reasons: firstly, macros take less disk space than compiled Fortran or C programs and are much easier to write, and secondly, the interaction with the user is extremely efficient; values of various parameters (plot size, title, symbols) can be changed interactively and the final plot printed. The dialogs are driven by menus.