Radix point
In mathematics and computing, a radix point (or radix character) is a symbol used to separate whole numbers (integers) from fractions. For example, the number [math]\displaystyle{ 1200.25 }[/math] represents the integer 1200 with a fractional part of 25, or 1200 and a fourth.
Because we use the decimal system, you probably know this point as the decimal point. "Decimal point" is a name specific to decimal, while "radix point" is a general name that can be used for any number system. Other number systems can have unique names too, like "binary point" for binary.
Most countries use either the period (.) or the comma (,) for the radix point. Some countries use them both in different contexts, such as Canada which uses periods in English and commas in French. A few countries use the Arabic decimal separator (٫).
Examples
In mathematical notation, each column of numbers represents a power of the radix, with a radix point noting the beginning of negative powers. For example, the base 10 number [math]\displaystyle{ 1234.56 }[/math] is read as follows:
| Powers | [math]\displaystyle{ 10^3 }[/math] | [math]\displaystyle{ 10^2 }[/math] | [math]\displaystyle{ 10^1 }[/math] | [math]\displaystyle{ 10^0 }[/math] | [math]\displaystyle{ 10^{-1} }[/math] | [math]\displaystyle{ 10^{-2} }[/math] |
|---|---|---|---|---|---|---|
| Value | 1 | 2 | 3 | 4 | 5 | 6 |
Hence, we can unwrap the representation as this:
- [math]\displaystyle{ \begin{align} &(1 \times 10^3) + (2 \times 10^2) + (3 \times 10^1) + (4 \times 10^0) + (5 \times 10^{-1}) + (6 \times 10^{-2})\\ &(1 \times 1000) + (2 \times 100) + (3 \times 10) + (4 \times 1) + (5 \times 0.1) + (6 \times 0.01)\\ &1000 + 200 + 30 + 4 + 0.5 + 0.06 \\ &1234.56 \end{align} }[/math]
To the left of the radix point is the integer part, made from positive powers. To the right of the radix point is the fractional part, made from negative powers.
Radix Point Media
Both a comma and a full stop (or period) are generally accepted decimal separators for international use. The apostrophe and Arabic decimal separator are also used in certain contexts.
Three ways to group the number ten thousand with digit group separators: Template:Blist*
The interpunct (·) used as a decimal separator in a British print from 1839
California milepost marker at mile 144.44
Decimal separators:* Dot (.)* Comma (,)* Both (may vary by location or other factors)* Arabic decimal separator (٫)* Data unavailable
