Mantissa: definition · Chip Field Guide

Beginner

The part of a stored number that holds its digits. More bits here means a more exact number.

Novice

The fraction bits of a floating-point number (also called the trailing significand). With $m$ mantissa bits, each power-of-two interval is split into $2^m$ equal steps, so $m$ sets the precision.

Expert

The stored fraction field; the significand is $1.M$ for normal numbers and $0.M$ for subnormals, so precision $p = m + 1$ . Relative spacing is $2^{-m}$ within a binade; the significand multiplier’s area grows roughly as $p^2$ .