A decimal calculation apparatus, which performs multidigit decimal calculation with the number of calculation digits set in a calculation instruction, includes a multidigit memory section which stores values with greater numbers of digits than the number of digits of a predetermined digit unit in a plurality of memory areas, a calculation-instruction memory section which stores the calculation instruction having the number of calculation digits and a type of calculation set therein, and a decimal calculation section which performs decimal calculation of sequentially calculating numerical values of corresponding digit units respectively stored in the plurality of memory areas of the multidigit memory section, digit unit by digit unit in the number of calculation digits set in the calculation instruction stored in calculation-instruction memory section, in decimal calculation according to type of calculation set in the calculation instruction stored in calculation-instruction memory section, and sequentially writing calculation results in the plurality of memory areas of the multidigit memory section digit unit by digit unit.
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