Implementation of C++ static data members

Static data members are data members declared in a class with the keyword static. In C++, static members are generally used instead of C global variables to achieve data sharing. The global variables of C and C++ are limited by 1. They can be modified arbitrarily and may easily conflict with other variable names. Therefore, in C++, 1 does not use global variables.

Static data members must be initialized outside of the class, and static data members can also reference, but not private data parts.

Here's an example:

#include <iostream>
#include <cstring>
using namespace std ; 
class Student 
{
 private :
 // Static member variable  
 static int age ;
 static float score ; 
 string name ;
 public :
 static int x , y ;
 // The constructor  
 Student();
 // The destructor  
 ~Student(); 
 // Set up information  
 int setstuinfo(int age , float score , string name);
 // The print information  
 int Printstuinfo();
};
// Static members must be initialized  
int Student::age = 24 ; 
float Student::score = 86.6 ; 
int Student::x = 100 ; 
int Student::y = 200 ;
Student::Student()
{
 this->name = "YYX" ;
 cout << this->name << endl ;
 cout << this->age << endl ; 
 cout << this->score << endl ; 
}
Student::~Student()
{
 this->name = "NULL";
 cout << this->name << endl ;
}
int Student::setstuinfo(int age , float score , string name)
{
 this->age = age ; 
 this->score = score ; 
 this->name = name ;
}
int Student::Printstuinfo()
{
 cout << this->name << endl ;
 cout << this->age << endl ; 
 cout << this->score << endl ; 
}
int main(void)
{
 Student stu1 ;
 // Pointer to the  
 Student *p ;
 p = &stu1 ;
 p->setstuinfo(25,96,"XXX");
 p->Printstuinfo();
 // A reference to a static member ----> Private members cannot be referenced 
 cout << p->x << endl ; 
 cout << p->y << endl ;
 Student::x = 80 ;
 Student::y = 90 ;
 cout << p->x << endl ; 
 cout << p->y << endl ;
 return 0 ;
}

Operation results:

YYX
24
86.6
XXX
25
96
100
200
80
90
NULL

conclusion