C++: 3. Scope resolution operator

The scope resolution operator ( :: ) is used for several reasons. For example: If the global variable name is same as local variable name, the scope resolution operator will be used to call the global variable. It is also used to define a function outside the class

To access a global variable when there is a local variable with same name:

#include <iostream>  

using namespace std;  

// declare global variable  

int num = 50;  

int main ()  

{  

// declare local variable   

int num = 100;  

// print the value of the variables  

cout << " The value of the local variable num: " << num;  

// use scope resolution operator (::) to access the global variable   

cout << "\n The value of the global variable num: " << ::num;   

return 0;  

}  

Output:- 

The value of the local variable num: 100

The value of the global variable num: 50

To define the member function outside of the class:

#include <iostream>  

using namespace std;  

class Operate  

{  

public:  

    // declaration of the member function  

    void fun();  

};  

// define the member function outside the class.  

void Operate::fun()   /* return_type Class_Name::function_name */  

{  

cout << " It is the member function of the class. ";  

}  

int main ()  

{  

 // create an object of the class Operate  

Operate op;  

op.fun();  

return 0;  

}  

Output:- 

It is the member function of the class.