Decimal64 floating-point format: Difference between revisions

Revision as of 13:17, 2 January 2025

Revision as of 15:33, 19 January 2025

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{{Short description|64-bit computer number format}}

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{{Use dmy dates|date=July 2020|cs1-dates=y}}

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The binary format of the same size supports a range from denormal-min {{gaps|±5|||||e=-324|}}, over normal-min with full 53-bit precision {{gaps|±2.225|073|858|507|201|e=-308|4}} to max {{gaps|±1.797|693|134|862|315|e=+308|7}}.

Because the significand for the [[IEEE 754]] decimal formats is not normalized, most values with less than 16 [[significant digits]] have multiple possible representations; 1000000 × 10^-2−2=100000 × 10^-1−1=10000 × 10⁰=1000 × 10¹ all have the value 10000. These sets of representations for a same value are called ''[[Cohort (floating point)|cohorts]]'', the different members can be used to denote how many digits of the value are known precisely. Each signed zero has 768 possible representations (1536 for all zeros, in two different cohorts).

== Encoding of decimal64 values ==

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|signaling NaN (with payload in significand)

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The DPD/3BCD transcoding for the declets is given by the following table. b9...b0 are the bits of the DPD, and d2...d0 are the three BCD digits.