Cpp Tutorial: Scope resolution operator in C++

#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;
    
}

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();
    
    
}

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;
}

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();
}

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