from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. that part of a floating-point number that contains its significant digits.


Sorry, no etymologies found.


  • If all of the first 40 bits of the double's significand are set, bits 1 to 39 are cleared and the exponent is incremented. - New Projects

  • Inf, the real's exponent and significand fields are filled so as to represent the largest value possible, the sign bit is transferred, and the code prInf is returned. - New Projects


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  • "In American English, the original word for this seems to have been mantissa (Burks et al.), and this usage remains common in computing and among computer scientists. However, the term significand was introduced by George Forsythe and Cleve Moler in 1967, and the use of mantissa for this purpose is discouraged by the IEEE floating-point standard committee and by some professionals such as William Kahan and Donald Knuth, because it conflicts with the pre-existing use of mantissa for the fractional part of a logarithm (see also common logarithm). For instance, Knuth adopts the third representation 0.12345 × 10+3 in the example above and calls 0.12345 the fraction part of the number; he adds: "it is an abuse of terminology to call the fraction part a mantissa, since this concept has quite a different meaning in connection with logarithms".

    The confusion is because scientific notation and floating-point representation are log-linear, not logarithmic. To multiply two numbers, given their logarithms, one just adds the characteristic (integer part) and the mantissa (fractional part). By contrast, to multiply two floating-point numbers, one adds the exponent (which is logarithmic) and multiplies the significand (which is linear)."

    -- (citations and emphasis removed)

    August 8, 2018