US Patent 7840617 Host device and memory system

A memory system includes a nonvolatile semiconductor memory and a controller which controls the semiconductor memory, the memory system being inserted into the host device. The host device further includes a file management system which allocates a cluster defined in a FAT file system to write data and manages the data allocated to the cluster by using management data including a file allocation table defined in the FAT file system and a directory entry. The directory entry includes a root directory entry serving as entry information of a root directory of an uppermost layer and a sub-directory entry serving as entry information of a sub-directory belonging to the root directory. The file system allocates the plurality of clusters in a predetermined range in which addresses are serial to the management data.