Importance

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Abstract

The portable electronic apparatus of the invention has a memory for storing externally-supplied data, and a central processing unit (CPU 15) for accessing the memory. The memory is divided into a plurality of areas. Each area has pointer data indicating a final address at which the data is written in that area, and a table that lists start and end addresses of each area. A write instruction to be supplied to the portable electronic apparatus consists of a write function code field, a write area designating field, a data string length field, and a data string. The CPU refers to the table based on the write area designating field of the supplied write instruction, reads an end address of the designated area and pointer data, and subtracts the pointer data from the end address, thereby calculating a memory capacity. Furthermore, the CPU compares the calculated memory capacity with the data string length of the write instruction, determines whether the data string can be entirely written, and writes the data string only when it is determined that it can be entirely written.

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First Claim