Decimal point, a mathematical symbol written as ".",is used to separate the integer part from the decimal part in decimal system. Although the decimal point is small, it plays a great role.

China has used decimal counting method since ancient times, and some practical units of measurement also use decimal, so it is easy to produce the concept of decimal. The first person to express this concept in words was Liu Hui in Wei and Jin Dynasties.

In the process of calculating pi, he used seven units, such as feet, inches, minutes, centimeters, millimeters, seconds and bumps. For the following units that suddenly become smaller, they are no longer named, and they are collectively called "micro numbers".