A medium, which is accessed by a reproducing/recording apparatus, having a read-only area in which commodity catalog information provided by a vendor is written and where only a read operation is allowed, and a writeable area in which predetermined commodity catalog information provided by a server is updated and where a write operation of user information for later retrieval is allowed. Using the medium, consumers can easily access the latest commodity catalog information at any time, and make secure purchases using identity verification methods using the latest commodity catalog information. The use of the medium and system accelerates the purchasing system so as to increase sales, files a purchase record on the consumer side, which provides a guarantee mechanism for refund or exchange in the future. Further, since the commodity catalog information is distributed online, labor and financial waste can be reduced.