Radix point

In mathematics and computing, a radix point (or radix character) is the symbol used in numerical representations to separate the integer part of the number (to the left of the radix point) from its fractional part (to the right of the radix point). In base-10 notation, the radix point is more commonly called the decimal point. "Radix point" is a general term that applies to all number bases (the prefix "deci-" implies base-10). Binary point implies base-2.

In English-speaking countries, the radix point is usually a small dot (.), placed either on the baseline or halfway between the baseline and the top of the numerals. In other regions, a comma (,) is usually used instead; see decimal separator for further information.

Example in base 10: 100.5

:100 is the integer to the left of the radix point, and 5 (meaning 5/10, or 1/2) is the fractional part to the right.

Example in binary: 1101.101

The binary number 1101.101 has the following digits:

power of 2: 3 2 1 0 -1 -2 -3 binary digit: 1 1 0 1 . 1 0 1

And has a decimal value of:

= 1*2^3 + 1*2^2 + 0*2^1 + 1*2^0 + 1*2^-1 + 0*2^-2 + 1*2^-3= 1*8 + 1*4 + 0*2 + 1*1 + 1*0.5 + 0*0.25 + 1*0.125= 8 + 4 + 0 + 1 + 0.5 + 0 + 0.125= 13.625

:"1101" to the left of the radix point is the binary representation of the base-10 number 13. To the right of the radix point is "101", which is the binary representation of the fraction 625/1000.