*
* =============  Case 6  ===============
*
* All lines beginning with an asterisk followed by at least ONE
* blank is a comment and is ignored.
*
* Now a key is added to the plot, two more curves are drawn
* with corresponding symbol and line types, the data is now
* sorted on alpw (the angle of attack), a (coarse) grid is added
* and the text content has been changed.
* 
pp
  plotfile PF scale .5 translate 2 2
  files r10 r11 r12 x cd y cl 
  text center top ?Average mach number is *mach f7.4*?
  auto
  grid
  psort alpw alpw alpw
  xlabel CD  ylabel CL
  lines 2 2 2
  symbols 1 2 3
  key 301 8.2 8.2 run i2 mach f7.4
  plot
  go