Significand
The significand (also mantissa or coefficient) is part of a number in scientific notation or a floating-point number, consisting of its significant digits. Depending on the interpretation of the exponent, the significand may represent an integer or a fraction. The word mantissa seems to have been introduced by Arthur Burks in 1946 writing for the Institute for Advanced Study at Princeton, although this use of the word is discouraged by the IEEE floating-point standard committee as well as some professionals such as the creator of the standard William Kahan.
The number 123.45 can be represented as a decimal floating-point number with the integer 12345 as the significand and a 10−2 power term also called characteristics, where −2 is the exponent (and 10 the base). Its value is given by the following arithmetic:
This same value can also be represented in normalized form with 1.2345 as the fractional coefficient, and +2 as the exponent (and 10 as the base):
Schmid, however, called this representation with a significand ranging between 1.0 and 10 a modified normalized form.
For base 2, this 1.xxxx form is also called a normalized significand.
Finally, the value can be represented in the format given by the Language Independent Arithmetic standard and several programming language standards, including Ada, C, Fortran and Modula-2, as:
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