What are the usage of classes and objects in C++?

C++ is an object-oriented programming language, where classes and objects play a very important role. A class is a user-defined data type that represents a category of objects with similar attributes and behaviors. An object is an instance of a class, possessing the attributes and behaviors defined by the class.

In C++, classes are defined using the keyword “class”, which can contain member variables and member functions. Objects are instances created from classes, allowing for the use of member functions and member variables to manipulate them.

Here is a simple example demonstrating how to define a class and create objects:

#include <iostream>
using namespace std;

// 定义一个类
class Person {
public:
    string name;
    int age;

    void display() {
        cout << "Name: " << name << endl;
        cout << "Age: " << age << endl;
    }
};

int main() {
    // 创建对象
    Person person1;
    
    // 设置对象的属性
    person1.name = "Alice";
    person1.age = 30;
    
    // 调用对象的成员函数
    person1.display();
    
    return 0;
}

In the example above, we defined a class called Person with two member variables, name and age, as well as a display() member function used to show the object’s properties. We then created an object named person1 in the main function, set its attribute values, and finally called the display() function to show the object’s properties.

By utilizing classes and objects, we can effectively organize and manage code, enhancing its reusability and maintainability. Additionally, object-oriented programming allows for a more accurate representation of entities and relationships in the real world.