Method of writing numbers in which the position of each number is related to the neighbouring position by a multiplier. The multiplier defines the base of the number system.

In the decimal number system, the base of the system is ten, so that the multiplier from one position to the next is 10, when we move to the right. When we move to the left the multiplier is \(\dfrac{1}{10}\).

### Examples

- 45.09 is a way to write the rational number \(\frac{4509}{100}\) in positional decimal notation. Therefore, it’s a decimal number.
- 1100.1 is a way to write the rational number \(\frac{25}{2}\) in positional binary notation. Therefore, it’s a binary number with a base of 2.