When a certain file is updated, a document management server determines whether a "registration state information mail" is set for that file, and after that, performs "self information mail" setting processing. Computer requests the document management server to transmit an electronic file, and prints and displays the electronic file according to an operation definition corresponding to the file format of the received electronic file. MFP inquires whether the document to be displayed is an electronic file stored in the document management server or an electronic file recorded on an external storage medium. Further, in response to an operation of a touch panel, MFP changes a magnifying power of display data, and rotates an image to change the direction by setting the central position of the rotation to a display center of an image being currently displayed.