All plot activities are accomplished by sending messages to plot objects. For example, every time a plot needs to be redrawn the system sends the plot the :redraw message. By defining a new method for this message you can change the way a plot is drawn. Similarly, when the mouse is moved or clicked in a plot the plot is sent the :do-mouse message. Menu items also send messages to their plots when they are selected. If you are interested in modifying plot behavior you may be able to get started by looking at the methods defined in the graphics files loaded on start up. Further details will be given in .