Patent ID: 8019800

Claim:
An access device that accesses an information recording device including a nonvolatile memory storing file data, the access device comprising: a file system control unit that manages a file using an extent information entry, a file allocation table, and an entry group, the extent information entry managing the file data in units of fixed-length blocks and including, as management information for a continuous area including one or more fixed-length blocks, information for identifying at least a position and a size of the continuous area, the file allocation table managing information indicating a link between the fixed-length blocks, and the entry group being generated for each file, and internally including one or more fixed-length entries storing management information including information about a name and a size of the file and information about a checksum of the one or more fixed-length entries, (1) wherein the file system control unit stores the extent information entry into an external area consisted of the fixed-length blocks, each of which has a predetermined length, the external area being external to the area of the entry group, (2) wherein the entry group includes an extent area designation entry including information for identifying a position and a size of the extent area, and (3) wherein the file system control unit includes an extensible file processing unit that, when accessing a file, controls access to the file based on the extent area designation entry and the extent area extent information entry when the entry group corresponding to the file includes the extent area designation entry, and a normal file processing unit that, when accessing a file, controls access to the file based on the file allocation table when the entry group corresponding to the file includes no extent area designation entry.