Implementation of C++ friend class

The friends in C++ can implement both friend functions and friend classes, meaning that a class can be a friend of another class. When a member of a class is a friend of another class, all its member functions are friends of another class and can access the private or public members of another class.

For example:

#include <iostream>
#include <cstring>
using namespace std ;
// Declaration of teacher class  
class Techer ;
// Students in class  
class Student 
{
 private:
 string name ;
 int age ; 
 char sex ; 
 int score ; 
 public :
 Student(string name , int age , char sex , int score);
 void stu_print(Techer &tech);
};
// The teacher class  
class Techer
{
 private:
 string name ;
 int age ; 
 char sex ; 
 int score ; 
 public :
 Techer(string name , int age , char sex , int score);
 // The statement 1 A metaclass 
 friend Student ;
};
//Student Class constructor implementation  
Student::Student(string name , int age , char sex , int score)
{
 this->name = name ; 
 this->age = age ; 
 this->sex = sex ; 
 this->score = score ;
}
//Techer Class constructor implementation 
Techer::Techer(string name , int age , char sex , int score)
{
 this->name = name ; 
 this->age = age ; 
 this->sex = sex ; 
 this->score = score ;
}
// print Student The private member and of the class Techer Private member of  
void Student::stu_print(Techer &tech)
{
 // with this A pointer accesses a member of this class  
 cout << this->name << endl ; 
 cout << this->age << endl ; 
 cout << this->sex << endl ; 
 cout << this->score << endl ;
 // access Techer The members of the class  
 cout << tech.name << endl ;
 cout << tech.age << endl ; 
 cout << tech.sex << endl ; 
 cout << tech.score << endl ;
}
int main(void)
{
 Student stu1("YYX",24,'N',86);
 Techer t1("hou",40,'N',99);
 stu1.stu_print(t1);
 return 0 ;
}

Operation results:

YYX
24
N
86
hou
40
N
99

conclusion