0**.**31

Positional notation can also be used with a base other than ten. Here is a number written using base two:

1 | 0 | 0 | . | 1 | 0 | 1 |

1×2^{2} | 0×2^{1} | 0×2^{0} | . | 1×2^{-1} | 0×2^{-2} | 1×2^{-3} |

When a particular power of the base is not needed, the digit '0' is used for
that position.
If the base is two, the point
` '`

is called a **.**' **binary point**.

In general,
the mark used to separate the fraction from the whole number
is called a **radix point**.
In many European nations,
the radix point "," is used.