15.15.17  Example 

     TD:CONTOUR
Draws a series of contour lines according to the Z scale.

     TD:CONTOUR SECONDARY 1,2,3,4,6,7,8,9,PRIMARY,20,LABEL,5,10
          or...

     TD:CONTOUR SECONDARY FROM 1 TO 9 BY 1 PRIMARY,20,LABEL,5,10
Draws  contours  for  Z=1  to 20.  Contour 5 and 10 are labeled.  Contours
5,10, and 20 will be SOLID, all others are dotted.
     TD:CONTOUR SAVE 10
Saves the contours for Z=10 as separate data sets.  No plot is produced.