To control data writing with high reliability without reducing the life of a nonvolatile memory in writing data in the nonvolatile memory from a volatile memory.

An information processor 10 includes a RAM 12 where the data is temporarily stored; and a flash ROM 13 where the data from the RAM is copied as backup information. When the data is copied in the flash ROM, a CPU 11 performs an erasing operation by sector unit with respect to the flash ROM, and then, copies the data by sector unit into the flash ROM. The RAM is divided into a plurality of data areas. Each one of the data areas has a size corresponding to a sector size. When the data is written in the flash ROM from the RAM, the CPU copies the data in the sector of the flash ROM at every data area and adds a writing serial number, which indicates writing times, whenever writing is performed.

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