In a printer system wherein one or a plurality of host computers use in common a single printer such as an expensive photo printer for electronic publishings of desktop publishings such as word processors, character format data of characters to be printed out is stored beforehand as character pattern data at a printer controller of the printer system. The host computer either stores minimum necessary character pattern data for monitor display or control, or stores no character pattern data. The character pattern data necessary for monitor display or control are used by transferring them from the printer controller to the host computer.