类class

类和成员函数（类外定义与类内定义）

#include <bits/stdc++.h>

using namespace std;

class student {
public:
    int name = 453;
    string c = "ASFASDF";

    void display() {
        cout << name << endl;
        cout << c;
    }

    int max(int a);

} stu1;

int student::max(int a) {
    cout << a + 3 << endl;
}

inline int en(int a) {
    return 1;
}

int main() {
    stu1.display();
    cout << en(4)<<endl;
    cout<<stu1.max(stu1.name);
    return 0;
}

含有构造函数的类声明，以及定义类对象的注意事项

#include <iostream>
#include <string>

using namespace std;
struct student {
    int name = 44;
};

string en(const std::string  a) {
    return a;
}

class stu {
public:
    int id;
    int num;
    string a;
    stu(int , int,string );
};
//含有构造参数的类不能在结束末尾直接定义 

//class stu {
//public:
//    int id;
//    int num;
//    string a;
//    stu(int , int,string );
//}s1;         错的
stu::stu(int x, int  y,string z) {
    id = x;
    num = y;
    a=z;
}

int main() {
    const string c = "sdafsa";
    stu s1 (12, 45, "fdsaf");
    cout << en(c)<<s1.id;
    return 0;
}