Decimal uses bases of 10; binary uses base 2. Which option lists the base for binary?

• A. 1
• B. 2
• C. 5
• D. 10

Answer: (B)

Binary uses base two. The base, or radix, is the number of digits a numeral system uses and determines how place values grow. In binary there are only two digits, 0 and 1, so each position represents a power of two: 2^0, 2^1, 2^2, and so on. That’s why the base for binary is two. Decimal, by contrast, uses base ten with digits 0–9, so its place values are powers of ten. In general, a system with five digits would be base five, and a base-one system isn’t used as a standard positional system.