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Integer representation of decimal numbers for exact computations



Javier Bernal, Christoph J. Witzgall


A scheme is presented and software is documented for representing as integers input decimal numbers that have been stored in a computer as double precision floating point numbers and for carrying out multiplications, additions and subtractions based on these numbers in an exact manner. The input decimal numbers must not have more than nine digits to the left of the decimal point. The decimal fractions of their floating point representations are all first rounded off at a pre-specified location, a location no more than nine digits away from the decimal point. The number of digits to the left of the decimal point for each input number besides not being allowed to exceed nine must then be such that the total number of digits from the leftmost digit of the number to the location where round-off is to occur does not exceed fourteen.
NIST Interagency/Internal Report (NISTIR) - 7144
Report Number


Bernal, J. and Witzgall, C. (2004), Integer representation of decimal numbers for exact computations, NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed May 22, 2024)


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Created October 1, 2004, Updated May 2, 2019