# File lib/spreadsheet/excel/writer/worksheet.rb, line 687
  def write_refmode
    # • The “RC” mode uses numeric indexes for rows and columns, for example
    #   “R(1)C(-1)”, or “R1C1:R2C2”.
    # • The “A1” mode uses characters for columns and numbers for rows, for
    #   example “B1”, or “$A$1:$B$2”.
    mode = 1 # 0 = RC mode; 1 = A1 mode
    write_op 0x000f, [mode].pack('v')
  end