PURPOSE: To attain an address designation with a zone symbol by preparing a zone symbol corresponding to respective zones in a data memory and an absolute address corresponding to it as a table onto a data memory.

CONSTITUTION: A PROM5 as a data memory is divided into a control table and the N pieces of user zones, and into the control table, the table of a zone symbol corresponding to respective zones and the absolute address of respective zones is stored. When a CPU4 executes the addressing, the CPU4 obtains the absolute address of a zone corresponding to the zone symbol designated from the external part from the above-mentioned control table, and executes an actual address designation to the PROM5 with the absolute address. Consequently, only by designating the symbol of a zone, the address designation at the time of the recording and at the time of the reading can be executed and simply, the writing and reading of the data can be executed.