1. A memory device comprising: a volatile memory; a first nonvolatile memory; a second nonvolatile memory configured to store management data indicating a relationship between an identifier of each of programs executed by a host system and an address of each of a plurality of regions of the volatile memory being allocated respectively to the programs; and a controller configured to save, in response to an event of power loss, data of the volatile memory to the first nonvolatile memory, wherein the controller is configured to: receive, after recovery of power, from the host system an identifier of a first program of the programs and an address indicating a first region of the volatile memory newly allocated to the first program by the host system; identify, based on the identifier of the first program, a region of the first nonvolatile memory where first data has been saved, wherein the first data is data of the region of the volatile memory being allocated to the first program before the power loss; restore the first data stored in the identified region of the first nonvolatile memory into the indicated first region of the volatile memory; and update the management data after the first data stored in the identified region of the first nonvolatile memory is restored, and change the address of the region of the volatile memory which corresponds to a program having a same identifier as the identifier of the first program to the address indicating the first region.