A portable data storage device is disclosed which includes an Interface for enabling the portable data storage device to be used for data transfer with a host Computer, and an Interface controller for controlling the interface. At least one of the surfaces which has a different designation than the surfaces on which the tabs and hook are located, is equipped with a button, one end of which is equipped with a first slide surface. The silver plating contributes to an excellent light reflectance and wire bonding efficiency of the inner part, whereas the gold flash plating contributes to an excellent resistance to corrosion and soldering efficiency of an outer part that is outside the package. When an initialization operation of the memory system is performed, the controller activates an operation standby signal after loading a portion of the drive data stored in the nonvolatile memory device into the working memory.