I. Definition:

Natural number refers to the number used to measure the number of things or to indicate the order of things. That is, the number 0, 1, 2, 3, 4 represents the number. Natural numbers start from 0, one by one, forming an infinite group. Natural numbers are ordered and infinite. Divided into even and odd numbers, composite numbers and prime numbers.

2. Disputes about 0:

Whether "0" is included in natural numbers is controversial. Some people think that natural numbers are positive integers, that is, counting from 1; Others think that natural numbers are non-negative integers, that is, counting from 0. By 2 1 century, no consensus has been reached on this issue.

Abroad, textbooks in some countries count 0 as a natural number. This is an artificial rule. In order to implement the international standards formulated by the International Organization for Standardization (ISO), China defines natural number set as containing element 0, and also to integrate with international standards as soon as possible.

The current nine-year compulsory education textbooks and senior high school textbooks (revised for trial implementation) call non-negative integer sets natural number set and n, and positive integer sets N+ or N*. This changed the previous view that 0 is not a natural number, and clearly pointed out that 0 is also an element of natural number set. 0 is also a rational number, and it is also neither negative nor positive.

The use of natural numbers:

1, count:

The most basic use of natural numbers is counting. Whether it is the shopping list in daily life, the population, or the number of experiments and data statistics in scientific research, natural numbers are needed to count. The simplicity and intuition of natural numbers make them the most commonly used counting tools.

2, ordinal number:

Natural numbers can be used to indicate the order of things. For example, natural numbers can be used to represent the ranking of the game, the position of the leaderboard and so on. Ordinal numbers are common in daily life, which helps to clarify the priority of things.

3. Operation:

Natural numbers are the basis of mathematical operations. Addition, subtraction, multiplication and division are all based on natural numbers. The operation law of natural numbers is also one of the foundations of mathematical theory. Through the operation of natural numbers, we can solve various practical problems and deduce more complicated mathematical concepts and formulas.

4. Measurement:

Natural numbers can be used to represent units of measurement. Physical quantities such as length, area and volume can be measured by natural numbers. The regularity of natural numbers makes it possible to compare, evaluate and analyze numbers through measurement, so as to better understand and explain physical phenomena.

5. Code:

Natural numbers play an important role in computer science. Computers use binary codes, while natural numbers provide an intuitive and easy-to-understand way to represent and process data. The operation rules and properties of natural numbers are also widely used in algorithm design and data structure.