Epics has been accepting special primary partilces (say, bunch of
particles generated other applications or Gecol etc).  Such primary
particles are put in a file of which name starts with "+", say 
+primary or  ../xxxx/yyy/+xyz etc. The file contains infomation
at its top about what kind of partilce propeties are included
in that file.  If, say, position info is missing in that file,
position is suppplied according to "sepicsfile" specification.
The file must be formatted (ascii) file. 

Now Epics can accept a binary file which is spciefied by the file
name with "-" at its top. However, it is a special one and you
cannot use it for primaries you have specified by "+" so far.
The "-" primary is  special for Light=22 case which uses the
result of Light=21; Its format contains some different stuff
than usual "+" case.   
Normally you may specify "-" file name for the OutPrimaryFile
in sepicsfile when Light=21.  With Light=22, you may specify
that file name by 'PrimaryFile' in 'sepicsfile'.

The output by Light=21 could be ascii (in that case 
OutPrimaryFile must be "+" file), although the file size
would become very large.



  Light 
  #----------------  
  header of the first event
  1ry info. 
  edep: sum of dE in each comp.   cn dE
  trailer                         cn= 0
  cghPath  or dE cell   (1ry)   code, subcode, charge....
   ...
  trailer            (code=-1000, subcode=event #.... )
  header of the 2nd event
   ...


 If Light=21;
     at	ini of all events
	open OutPrimaryFile
	assign OutPrimEff= OutPrimaryFileNo
	write header
	open scratch file (with 16=IoScratch)
     at ini of each event
	rewind  IoScratch
        assign OutPrimEff = IoScratch

      track for Cerenkov is put always on OutPrimEff
        when First interaction occurs.
A)	   get incident info. and first interaction info.
	   write event # and incident/first int. info
	   on OutPrimaryFileNo
	   rewind OutPrimEff 	    	   
	   cp OutPrimEff data into OutPrimaryFileNo
	   assign OutPrimEff to OutPrimaryFileNo
        
       at end of the event
           judge if no interaction.
	    if so, do A)
           endif
	   push enery deposit in cells on OutPrimEff
	   write end mark   on OutPrimEff
	   write  energy deposit in each comp. on OutPrimEff
	   write end event mark

	   
If Light=22
	at ini of all events
	open PrimaryFile
	read header
    at ini of each event
	read event # and inciden info. First col info.
		
	read path info. for Cerenkov and push in stack
	read cell dE info. for Sciti. and push in stack
	
	read dE of each comp. 
	start event generation: (light tracking).



