A direct set of integers is a set of all integers. It includes all positive integers, all negative integers and zeros. In mathematics, integer sets are usually represented by z.

Extended data:

N stands for the set of natural numbers in the set. A non-negative integer set is a specific set, which refers to the set of all natural numbers, and is commonly represented by the symbol n. Non-negative integers include positive integers and zeros. A set of nonnegative integers is a countable set.

Q stands for rational number set. The set of rational numbers, that is, the set of all rational numbers, is represented by the bold letter Q, and the set of rational numbers is a subset of the set of real numbers. The set of rational numbers is an infinite set with no maximum and minimum.

R stands for real number set. Generally speaking, a real number set is a set that usually contains all rational numbers and irrational numbers, and is usually represented by the capital letter R.

N+ represents a set of positive integers. The set of all positive integers is called a positive integer set.