The present invention realizes electronic commerce by providing a portable terminal (501). The portable terminal comprises a receiver, a barcode former, a display (590) and a detector (725). The receiver receives data representing product information and service information. The barcode former forms barcode data, based on the data received, the barcode data including a plurality of display barcodes, information defining the display order of the barcodes and information representing an end of the display of the plurality of display barcodes. The display (590) displays the barcode data generated by the barcode former. The detector (725) detects light or a signal from a barcode reader (708). The detection result of the detector influences the switching of the display from the currently displayed barcode to the display barcode next in the display order. The barcode reader is provided at a shop terminal etc. to read one of the plurality of barcodes.