According to one embodiment, a non-transitory medium, a controller, a memory, an extension function section, and an extension register. The controller controls the non-transitory medium. The memory which is serving as a work area is connected to the controller. The extension function section is controlled by the controller. The extension register which is provided on the memory is provided with a certain block length capable of defining an extension function of the extension function section. The controller processes a first command to write header data of a command to operate the extension function section to the extension function section through the extension register, and a second command to read header data of a response from the extension function section through the extension register.