SEMICONDUCTOR MEMORY

PURPOSE:To eliminate the need for write access to a subdirectory on a memory part and improve the performance in such a case by storing information on the subdirectory not in the memory part, but in a subdirectory storage part when a request for writing to the subdirectory is accepted. CONSTITUTION:This semiconductor memory is equipped with a subdirectory storage part 111 which consists of an overwritable nonvolatile memory and stores information in the subdirectory when the request to write data in the subdirectory whose position is indicated by the directory storage part 109 is received. Thus, when the request for writing to the subdirectory is received, the information is written not in the memory part 106, but in the subdirectory storage part 111. Consequently, even when a file under the control of the subdirectory is deleted or when data which are larger than the current data capacity are written, the rewriting of the memory part 106 can be suppressed and the performance of the device 101 is therefore improved.