1. A multifunction device having a plurality of functions and capable of being connected to a computer via a universal serial bus (USB) interface, the computer having an operating system (OS) installed thereon that recognizes the multifunction device as a device having at least one logic unit capable of transferring data according to a USB-compliant system such that the computer can use the plurality of functions of the multifunction device by exchanging input/output data with the logic unit, at least one of the at least one logic unit being a compound logic unit corresponding to two or more specific functions among the plurality of functions, the multifunction device comprising: a controlling unit that, when the computer has transferred output data with an actual data section to the compound logic unit, determines which one of the two or more specific functions the transferred output data is for controlling, based on unique standard data included in the actual data section, and that controls the determined function based on the output data, the controlling unit storing unique standard data in an actual data section of input data to be transferred to the computer as a result of controlling the function, the unique standard data indicating from which one of the two or more specific functions the input data is to be transferred, and transferring the input data to the computer as data from the compound logic unit.