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