1. A method, to be executed by an application program, for controlling a memory system provided with a nonvolatile memory, the method comprising: acquiring an unused memory area from an operating system installed in an information processing apparatus provided with the memory system; prohibiting the acquired unused memory area from being used by any application program other than the above application program; acquiring the address of the acquired unused memory area; and notifying the address of the acquired unused memory area to the memory system, wherein prohibition state put by the prohibiting is preserved until receiving a change instruction.