anchor.diff:  
     !> @ingroup Lib_VTK_IOPrivateProcedure
     !> @{
  +  !> Function for open/close field data tag.
  +  !> @return E_IO: integer(I4P) error flag
  +  function VTK_FLD_XML_OC(fld_action) result(E_IO)
  +  !---------------------------------------------------------------------------------------------------------------------------------
  +  implicit none
  +  character(*), intent(IN):: fld_action !< Field data tag action: OPEN or CLOSE tag.
  +  integer(I4P)::             E_IO       !< Input/Output inquiring flag: $0$ if IO is done, $> 0$ if IO is not done.
  +  !---------------------------------------------------------------------------------------------------------------------------------
  +
  +  !---------------------------------------------------------------------------------------------------------------------------------
  +  select case(trim(Upper_Case(fld_action)))
  +  case('OPEN')
  +    select case(f_out)
  +    case(f_out_ascii)
  +      write(unit=Unit_VTK,fmt='(A)',iostat=E_IO)repeat(' ',indent)//'<FieldData>' ; indent = indent + 2
  +    case(f_out_binary)
  +      write(unit=Unit_VTK,iostat=E_IO)repeat(' ',indent)//'<FieldData>' ; indent = indent + 2
  +    endselect
  +  case('CLOSE')
  +    select case(f_out)
  +    case(f_out_ascii)
  +      indent = indent - 2 ; write(unit=Unit_VTK,fmt='(A)',iostat=E_IO)repeat(' ',indent)//'</FieldData>'
  +    case(f_out_binary)
  +      indent = indent - 2 ; write(unit=Unit_VTK,iostat=E_IO)repeat(' ',indent)//'</FieldData>'
  +    endselect
  +  endselect
  +  return
  +  !---------------------------------------------------------------------------------------------------------------------------------
  +  endfunction VTK_FLD_XML_OC
  +
     !> Function for saving field data (global auxiliary data, e.g. time, step number, data set name...) (R8P).
     !> @return E_IO: integer(I4P) error flag
     function VTK_FLD_XML_R8(fld,fname) result(E_IO)
  
positive.code:   !---------------------------------------------------------------------------------------------------------------------------------
    select case(f_out)
    case(f_out_ascii)
      write(unit=Unit_VTK,fmt='(A)',iostat=E_IO)repeat(' ',indent)//'<FieldData>' ; indent = indent + 2
      s_buffer = repeat(' ',indent)//'<DataArray type="Int16" NumberOfComponents="1" Name="'//trim(fname)//'" format="ascii">'// &
                 trim(str(n=fld))//'</DataArray>'
      write(unit=Unit_VTK,fmt='(A)',iostat=E_IO)trim(s_buffer)
      indent = indent - 2 ; write(unit=Unit_VTK,fmt='(A)',iostat=E_IO)repeat(' ',indent)//'</FieldData>'
    case(f_out_binary)
      write(unit=Unit_VTK,iostat=E_IO)repeat(' ',indent)//'<FieldData>' ; indent = indent + 2
      s_buffer = repeat(' ',indent)//'<DataArray type="Int16" NumberOfComponents="1" Name="'//trim(fname)//'" format="ascii">'// &
                 trim(str(n=fld))//'</DataArray>'
      write(unit=Unit_VTK,iostat=E_IO)trim(s_buffer)
      indent = indent - 2 ; write(unit=Unit_VTK,iostat=E_IO)repeat(' ',indent)//'</FieldData>'
    endselect
    return
    !---------------------------------------------------------------------------------------------------------------------------------
  
negative.code:   !---------------------------------------------------------------------------------------------------------------------------------
    select case(f_out)
    case(f_out_ascii)
      s_buffer = repeat(' ',indent)//'<DataArray type="Int8" NumberOfTuples="1" Name="'//trim(fname)//'" format="ascii">'// &
                 trim(str(n=fld))//'</DataArray>'
      write(unit=Unit_VTK,fmt='(A)',iostat=E_IO)trim(s_buffer)
    case(f_out_binary)
      s_buffer = repeat(' ',indent)//'<DataArray type="Int8" NumberOfTuples="1" Name="'//trim(fname)//'" format="ascii">'// &
                 trim(str(n=fld))//'</DataArray>'
      write(unit=Unit_VTK,iostat=E_IO)trim(s_buffer)
    endselect
    return
    !---------------------------------------------------------------------------------------------------------------------------------
  