1, positive integer
Like an integer, a positive integer is a countable infinite set. In number theory, positive integers, namely 1, 2, 3 ...; But in set theory and computer science, natural numbers usually refer to non-negative integers, that is, the set of positive integers and 0. It can also be said that all natural numbers other than 0 are positive integers. Positive integers can be divided into prime numbers, 1 and composite numbers. A positive integer may or may not have a plus sign.
A positive integer, an integer greater than 0, is also the intersection of positive numbers and integers. Positive integers can be divided into prime numbers, 1 and composite numbers. A positive integer may or may not have a plus sign. For example:+1, +6, 3, 5, these are all positive integers. 0 is neither a positive integer nor a negative integer. 0 is an integer.
2. Integer classification
We divide integers into three categories by 0: positive integers, that is, integers greater than 0, such as 1, 2. 0 is neither a positive integer nor a negative integer. Negative integer, that is, an integer less than 0, for example,-1, -2. Classification of positive integers, we know that a classification method of positive integers is based on the number of divisors or product factors, such as only two. Of course, we have always stressed that these two are 1 and ourselves. We call them prime numbers or prime numbers, and those more than two are called composite numbers.
3. Natural numbers
Natural number is the number we use to calculate the number of objects and the order of things, and it is also the most recognized number in human civilization. For example, there are 1 sun in the sky and three tribes on the ground. Natural numbers start from 0, and then one by one, form an infinite whole. The set of natural numbers includes 0 and positive integers, and can be divided into even and odd numbers, prime numbers, composite numbers and so on.
Decimal is one of integer, decimal point and digits after decimal point. For example, the most commonly used pi is a typical decimal. Decimals are used to represent objects that are not integers after measurement in daily life. Adding integers is convenient for measuring objects.