A communication system comprising: an information processing unit; a terminal device for transmitting packet input data to the information processing unit through packet communication according to a predetermined method in a predetermined format and with a predetermined capacity; and an extension apparatus connected to the terminal device in an attachable and removable manner, wherein the terminal device comprises an operation input means for receiving an operation input from a user, a packet generation means for making the operation input data obtained from the operation input means into a packet so as to generate the packet input data, a storage means for storing integrated scenario information defining a region allotted for the extension apparatus within data regions for the packet input data, and an extended data reception means for receiving extended input data from the connected extension apparatus, and wherein the packet generation means generates the packet input data by integrating the extended input data and the operation input data, according to the integrated scenario information stored in the storage means when the extension apparatus is connected to the terminal device; characterized in that the integrated scenario information is prestored in the extension apparatus; and the terminal device obtains integrated scenario information from the extension apparatus when the extension apparatus is connected thereto. an information processing unit; a terminal device for transmitting packet input data to the information processing unit through packet communication according to a predetermined method in a predetermined format and with a predetermined capacity; and an extension apparatus connected to the terminal device in an attachable and removable manner, wherein the terminal device comprises an operation input means for receiving an operation input from a user, a packet generation means for making the operation input data obtained from the operation input means into a packet so as to generate the packet input data, a storage means for storing integrated scenario information defining a region allotted for the extension apparatus within data regions for the packet input data, and an extended data reception means for receiving extended input data from the connected extension apparatus, and wherein an operation input means for receiving an operation input from a user, a packet generation means for making the operation input data obtained from the operation input means into a packet so as to generate the packet input data, a storage means for storing integrated scenario information defining a region allotted for the extension apparatus within data regions for the packet input data, and an extended data reception means for receiving extended input data from the connected extension apparatus, and wherein the packet generation means generates the packet input data by integrating the extended input data and the operation input data, according to the integrated scenario information stored in the storage means when the extension apparatus is connected to the terminal device; characterized in that the integrated scenario information is prestored in the extension apparatus; and the terminal device obtains integrated scenario information from the extension apparatus when the extension apparatus is connected thereto.