Patent ID: 6871259

Claim:
A file system including a non-volatile semiconductor memory device having a plurality of banks, each of said banks including a plurality of blocks, said non-volatile semiconductor memory device being erasable by said bank, said plurality of banks being divided into at least one update data bank, at least one merge bank and a data bank, said file system comprising: an update data storage unit for storing update data corresponding to a data rewrite command into said update data bank; a latest data selection unit for selecting, when a predetermined first condition is satisfied, latest update data for each block from the update data stored in said update data bank; and a processing unit for processing said selected latest update data, said processing unit including a first merge data storage unit for storing said selected latest update data into a first block in said merge bank, an associated data selection unit for selecting data associated with said latest update data from said data bank, a second merge data storage unit for storing said selected data into a second block in said merge bank, and a setting unit for setting the merge bank storing said latest update data and the data associated with said latest update data as a new data bank.