C++ Visibility Modes

Visibility Modes

Public mode: If we derive a class from a public base class. Then the public member of the parent class will become public in the derived class and protected members of the base class will become protected in derived class.
Protected mode: If we derive a child-class from a Protected base class. Then both public members and protected members of the base class will become protected in the derived class.
Private mode: If we derive a subclass from a Private base class. Then both public members and protected members of the base class will become Private in the derived class.


class A
{
public:
    int x;
protected:
    int y;
private:
    int z;
};
 
class B: public A
{
    // x is public
    // y is protected
    // z is not accessible from B
};
 
class C: protected A
{
    // x is protected
    // y is protected
    // z is not accessible from C
};
 
class D : private A    // 'private' is default for classes
{
    // x is private
    // y is private
    // z is not accessible from D
};

The table below is a simple representation of how the base class members are inherited in each mode of inheritance.

‍

The table below is a simple representation of how the base class members are inherited in each mode of inheritance.



#include 
using namespace std;

//base parent class
class Parent
{
	// protected data members
	protected:
	int rollNo;
	
};

//  derived child class from public base class
class Child : public Parent
{
	public:
	void setrollNo(int id)
	{
		
		// Child class is able to access the inherited
		// protected data members of base class
		
		rollNo = id;
		
	}
	
	void displayId()
	{
		cout << "id_protected is: " << id_protected << endl;
	}
};

// main function
int main() {
	
	Child obj1;
	
	// member function of the derived class can
	// access the protected data members of the base class
	
	obj1.setId(19);
	obj1.displayId();
	return 0;
}


Output:
id_protected is: 19