void autolegend(on_off) LEGEND.C Level 2
char on_off Controls the automatic line style and color changing of the legend feature. 
 = 0 turns it off.
 = 1 turns it on (default).
The legend feature automatically changes the line styles and colors of your curves when using curve(). Use autolegend(0) to turn this feature off. autolegend() must not be called until all of the calls to legend() have been made.