Decimal64 floating-point format: Difference between revisions

Revision as of 20:21, 15 February 2014

Revision as of 20:23, 15 February 2014

Line 12:

IEEE 754 allows two alternative representation methods for decimal64 values. The standard does not specify how to signify which representation is used, for instance in a situation where decimal64 values are communicated between systems:

* In the [[#Binary integer significand field|binary representation method]], the 16-digit significand is represented as a binary coded positive integer, based on [[binary integer decimal]].

* In the [[#Densely packed decimal significand field|decimal representation method]], the 16-digit significand is represented as a decimal coded positive integer, based on [[densely packed decimal]] wherewith 5 groups of 3 digits (except the most significant digit encoded specially) are each represented in declets (10 -bit eachsequences).

Both alternatives provide exactly the same range of representable numbers: 16 digits of significand and 3×2⁸ = 768 possible decimal exponent values. (All the possible decimal exponent values storable in a [[binary64]] number are representable in decimal64, and most bits of the significand of a binary64]] are stored keeping roughly the same number of decimal digits in the significand.)