1. A memory system comprising: a Flash-EEPROM memory in which a plurality of memory cells having a floating gate or a charge trapping layer and capable of electrically erasing and writing data are arranged; a control circuit that controls a cache memory and the Flash-EEPROM memory; and an interface circuit that communicates with outside, wherein a plurality of group data and a plurality of flag data for storing presence of inversion of all bits of respective group data are stored in a memory area of the Flash-EEPROM memory.