MEMORY SYSTEM AND MEMORY CARD

PROBLEM TO BE SOLVED: To shorten data write time, to eliminate the number of times of rewrite to a specified area and to eliminate the destruction of data even by sudden power disconnection from the outside. SOLUTION: Write data are tentatively stored in a RAM 302 and then, written to a flash memory 301. An access history from a host system is stored in a memory 304, and based on the information, the data of an area with the large number of times of access are arranged not inside the flash memory but inside the RAM 302. After the power disconnection from the outside, an internal circuit is operated by an internal auxiliary power source 303 and the erasure operation of the flash memory 301 and the write to the flash memory 301 of the data arranged inside the RAM 302 are performed. The auxiliary power source 303 is charged while power is supplied from the outside.