A binary number is a number expressed in the base-2 numeral system or
binary numeral system , a method for representing numbers that uses only
two symbols for the natural numbers: typically "0" (zero) and "1" (one). A
binary number may also refer to a rational number that has a finite
representation in the binary numeral system, that is, the quotient of an
integer by a power of two.
The base-2 numeral system is a positional notation with a radix of 2. Each
digit is referred to as a bit, or binary digit.