C++ Chapter 20: Scope resolution operator in C++

In this tutorial we shall see different uses of Scope Resolution Operator

1. To access a global variable.
2. In case of multiple inheritance.
3. To Access class static variables.
4. To access static member function
5. To define a function outside the class.

1. To access a global variable.

#include <iostream>
using namespace std;

int num = 10;

int main(void)
{

    int num = 20;

    cout<<"Local num value "<<num<<endl;

    cout<<"Global num value "<<::num<<endl;
}

Output:

Local num value 20

Global num value 10

2. In case of multiple inheritance.

#include <iostream>
using namespace std;

class Base
{

public:
    int num;

    Base()
    {
        num = 10;
    }
};

class Derived : public Base
{
public:
    int num;

    Derived()
    {
        num = 20;
    }

    void display()
    {
        cout<<"The base class num is "<<Base::num<<endl;

        cout<<"The derived class num is "<<Derived::num<<endl;
    }
};


int main(void)
{

    Derived dObj;

    dObj.display();
}

Output:

The base class num is 10

The derived class num is 20

3. To Access class static variables.

#include <iostream>
using namespace std;

class Base
{

public:

    static int num;
};

int Base::num = 20;

int main(void)

{

    cout<<"The static value is "<<Base::num<<endl;

}

Output:

The static value is 20

4. To access static member function

#include <iostream>
using namespace std;

class Base
{

public:
    static void display()
    {
        cout<<"The display function"<<endl;
    }
};

int main(void)
{

    Base::display();

}

Output:

The display function

5. To define a function outside the class.

#include <iostream>
using namespace std;

class Base
{

public:

    void display();

};

void Base::display()
{
    cout<<"In display function"<<endl;
}

int main(void)
{

    Base obj;
    obj.display();

}

Output:

In display function