binary decimal

binary decimal (plural binary decimals)

1. (dated) A binary (base-2) numeral.
   • 1938, G. H. Hardy, E. M. Wright, An Introduction to the Theory of Numbers, section 9.7:

     Any positive integer up to ${\displaystyle 2^{n}-1}$ inclusive can be expressed uniquely as a binary decimal of ${\displaystyle n}$ figures, i.e., as a sum ${\displaystyle \sum _{0}^{n-1}a_{s}2^{s}}$, where every ${\displaystyle a_{s}}$ is ${\displaystyle 0}$ or ${\displaystyle 1}$.

2. (informal) Used other than figuratively or idiomatically: A decimal (numeral written as a concatenation of successive negative powers of the base) in base 2..

• binary-coded decimal

• Mathematics Stack Exchange: "What is the origin of the (nearly obsolete) term 'binary decimal'?"