anchor.diff:        read(90,iostat=ierro) sixtit,commen,cdate,ctime,                  &
        &progrm,ifipa,ilapa,itopa,icode,numl
          imax=itopa
  -       turns=numl+1
          if(ifipa.eq.ilapa) then
             rph=1              !--rph is record per header 
          else 
  
positive.code:       endif
   
        if(rph.eq.2) then
          do l=1,turns,10
   40     read(90,iostat=ierro) ia,ifipa,b,c,d,e,f,g,h,p,ilapa,b,          &
       &c1,d1,e1,f1,g1,h1,p1
          if(ifipa.ne.i) then
  
negative.code:       do k=1,imax,rph
           read(90)
        enddo 
        read(90) ia
        do k=1,imax-1,rph
           read(90)
        enddo
        read(90) ib
        turns=numl/(ib-ia)+1   !counts how many records of tracking data per paricle(pair)
        rewind 90
        do k=1,imax,rph
           read(90)
        enddo
        if(rph.eq.1) then
          do l=1,turns
   30     read(90,iostat=ierro) ia,ifipa,b,c,d,e,f,g,h,p
  