
[ev] is the optional event number. If omitted, 1 is assumed 
 xxxx can be
  all      for showing all tracks with no hidden mode
  allh     for  //                     hidden mode
  only+-   for  //    only charged particles with no hidden mode
  only+-h  for  //    only charged particles with  hidden mode
  only0    for  //    only neutral particles with no hidden mode
  only0h   for  //    only neutral particles with  hidden mode
  sort     for  //  only charged particles with different colors
                    for different  particle codes.   No hidden mode
  sort+-   for  //  only charged particles with differenct colors
                    for different particle codes and charges.
                   (no hidden mode)

5) To show 20 events sequentially, use
 
	a = -1 
	call "slide"

  if a =-1, after display of 1 event, system wait your "return"
     a = n (>0) //                        system wait  n sec.


  
