Patent ID: 8103819

Claim:
An information storage device comprising: nonvolatile semiconductor memory which stores management data items accompanying content data items and is configured to erase management data items in units of blocks; and a controller which performs control for: forming, in the nonvolatile semiconductor memory, a working area in which management data items may be temporarily stored and a storage area in which a copy of all or part of management data items stored in the working area may be stored; storing management data items in the working area sequentially; monitoring free space of the working area in which additional management data items may be stored, wherein when the free space falls below a predetermined value, management data items stored in the working area are copied to the storage area, and management data items in the working area, which are copied to the storage area, are assigned a first status indicating that storage processing to the storage area is completed; and only if a block in the working area is filled with management data items which are assigned the first status, erasing the management data items stored in that block.