To provide a technology enabling a terminal device to use various functions provided in a data processing device without the use of a device driver. A multifunction device executes a process for implementing a function indicated by instruction data when such instruction data is stored in a shared area of the RAM. Here, the shared area of the RAM in which the instruction data is stored can be recognized by a personal computer connected to the multifunction device as a storage area that can be accessed through the file system, which is a function provided as a standard feature of the operating system. Accordingly, operations of the multifunction device can be controlled from the personal computer end simply by storing instruction data in the shared area via the operating system, eliminating the need for a special device driver to control the operations of the multifunction device.