The point in the decimal is called the decimal point, which is the dividing line between the integer part and the decimal part of a decimal. Decimals with zero integer parts are called pure decimals, and decimals with non-zero integer parts are called decimals.
Origin of decimal point:
During the Song and Yuan Dynasties, the concept of decimal was further popularized and expressed more clearly. Yang Hui's Daily Arithmetic (1262) has a formula for converting two catties: "If you find one, it will be every six or twenty-five; Second, seek, abdicate one, two, five ",where" every other position "and" abdication "already have the meaning of indicating the position of decimal point. In Qin dynasty, units are placed under the chip representing integer units. For example,-Ⅲ-Ⅱ means 13. 12 inch, which is the earliest decimal representation in the world.
The basic content of finite decimal:
Counting units are one (one), ten, hundred, thousand and ten thousand, all of which are called counting units. Where "one" is the basic unit of counting. 10 is 10, 10 is 100, 10 is 100 billion, and the advance rate between every two adjacent counting units is 10. This counting method is called decimal counting method.
When measuring an object, you often get a number that is not an integer. So the ancients invented decimals to supplement integers. Decimal is a special form of decimal. Decimals can be divided into finite decimals and infinite decimals, and infinite decimals can be divided into infinite cyclic decimals and infinite acyclic decimals. All fractions can be expressed as decimals, and all decimals can be expressed as component numbers except infinite acyclic decimals (irrational numbers).