An image displaying system has a projector, an MFP and a client terminal device that are connected to one another via a LAN. In a setting screen of a printer driver installed in the client terminal device, a print job or a projection job is selected, and an image file for execution of the selected job is specified, and job data having header information and image data of the specified image file is generated and transmitted to the MFP. When the received job is an image displaying job, the MFP transmits image data pertaining to the image displaying job to the projector for displaying an image. Accordingly, convenience of the MFP having the projector connected thereto is enhanced.