anchor.diff:    integer :: inUnit = 90
     integer :: outUnit = 91
   
  -  integer :: myOutUnit = output_unit
  +  integer :: textOutUnit = output_unit
   
     ! Temp arrays for I/O
     character(len=80), private :: sixtit,commen
  
positive.code:     close(inUnit)
  
      if(itopa <= 0) then
        write(myOutUnit,'(a)')    "ERR in numSTFpairs: Corrupt itopa in first header of file '" // ifname // "'"
        write(myOutUnit,'(a,i0,a)') "itopa = ", itopa, " <= 0"
        stop 1
      end if
  
      if (modulo(itopa,2) /= 0) then
        write(myOutUnit,'(a)')    "ERR in numSTFpairs: Number of particles not divisible by 2."
        write(myOutUnit,'(a,i6)') "ERR in numSTFpairs: itopa = ", itopa
        stop 1
      end if
  
  
negative.code: 
          ntwin = ilapa-ifipa+1
          if (.not. (ntwin == 1 .or. ntwin == 2)) then
            write(textOutUnit,'(a)' ) "Error when reading header; ifipa=",ifipa, "ilapa=",ilapa,"ntwin=",ntwin
            stop 1
          end if
  
  