JPS6412332A - Decimal arithmetic unit - Google Patents

Abstract

PURPOSE:To eliminate an arithmetic operation for an invalid digit and to improve computing processing speed, by performing a prescribed decimal arithmetic operation only by the number of effective digits for decimal data to be computed and computing decimal data based on effective digit number data. CONSTITUTION:In a memory 10, the effective digit number data of the decimal data is stored with the decimal data. The least significant addresses and the number of digits of those data are designated and read out, and are stored in a register 11 to be added. The same data as the above data for the decimal data to be added in the memory 10 is read out, and is stored in an adding data register 12. A binary addition part 13 adds the data to be added and correction data, and stores it in an intermediate result data register 15. Next, the above data is added on the adding data, and it is stored in an intermediate result data register 16. At this time, the binary addition part 13 executes the binary addition of the number of effective digits.