1. A multifunction device configured to perform a plurality of functions and configured to connect to a computer via a universal serial bus (USB) interface, the computer comprising an operating system (OS) installed thereon that recognizes the multifunction device as a device comprising a plurality of logic units, each logic unit of the plurality of logic units configured to transfer data according to a USB-compliant system, such that the computer uses the plurality of functions of the multifunction device by exchanging input/output data with the plurality of logic units, at least one logic unit of the plurality of logic units being a compound logic unit corresponding to two or more specific functions among the plurality of functions, the multifunction device comprising: a controlling unit configured to determine which one of the two or more specific functions particular output data is for controlling, based on unique standard data comprised in an actual data section, when the computer has transferred the particular output data with the actual data section to the compound logic unit based on a Logical Unit Number (LUN) corresponding to the compound logic unit, wherein the controlling unit is configured to control the determined one function based on the particular output data, wherein the unique standard data is different from the LUN, wherein the controlling unit is configured to store unique standard data in an actual data section of input data to be transferred to the computer as a result of controlling the determined one function, the unique standard data indicating from which one of the two or more specific functions the input data is to be transferred, and wherein the controlling unit is configured to transfer the input data to the computer as data from the compound logic unit.