C++: 7. Inheritance

In C++, inheritance is a process in which one object acquires all the properties and behaviors of its parent object automatically. In such way, you can reuse, extend or modify the attributes and behaviors which are defined in other class.

In C++, the class which inherits the members of another class is called derived class and the class whose members are inherited is called base class. The derived class is the specialized class for the base class.

Single Level Inheritance

When one class inherits another class, it is known as single level inheritance.

Example:- 

#include <iostream>  

using namespace std;  

 class Account {  

   public:  

   float salary = 60000;   

 };  

   class Programmer: public Account {  

   public:  

   float bonus = 5000;    

   };       

int main(void) {  

     Programmer p1;  

     cout<<"Salary: "<<p1.salary<<endl;    

     cout<<"Bonus: "<<p1.bonus<<endl;    

    return 0;  

}  

Output:- 

Salary: 60000

Bonus: 5000

Multiple Inheritance

Multiple Inheritance is a feature of C++ where a class can inherit from more than one class. i.e one subclass is inherited from more than one base class.

Example:- 

#include <iostream>

 

using namespace std;

// Base class Shape

class Shape {

   public:

      void setWidth(int w) {

         width = w;

      }

      void setHeight(int h) {

         height = h;

      }

      

   protected:

      int width;

      int height;

};

// Base class PaintCost

class PaintCost {

   public:

      int getCost(int area) {

         return area * 70;

      }

};

// Derived class

class Rectangle: public Shape, public PaintCost {

   public:

      int getArea() {

         return (width * height); 

      }

};

int main(void) {

   Rectangle Rect;

   int area;

 

   Rect.setWidth(5);

   Rect.setHeight(7);

   area = Rect.getArea();

   

   // Print the area of the object.

   cout << "Total area: " << Rect.getArea() << endl;

   // Print the total cost of painting

   cout << "Total paint cost: $" << Rect.getCost(area) << endl;

   return 0;

}

Output:- 

Total area: 35

Total paint cost: $2450

Multi Level Inheritance

When one class inherits another class which is further inherited by another class, it is known as multi level inheritance in C++. 

Example:- 

#include <iostream>

using namespace std;

class base //single base class

{

  public:

  int x;

  void getdata()

  {

     cout << "Enter value of x= "; cin >> x;

  }

};

class derive1 : public base // derived class from base class

{

  public:

  int y;

  void readdata()

  {

      cout << "\nEnter value of y= "; cin >> y;

  }

};

class derive2 : public derive1   // derived from class derive1

{

  private:

  int z;

  public:

  void indata()

  {

     cout << "\nEnter value of z= "; cin >> z;

  }

  void product()

  {

      cout << "\nProduct= " << x * y * z;

  }

};

int main()

{

     derive2 a;      //object of derived class

     a.getdata();

     a.readdata();

     a.indata();

     a.product();

     return 0;

}

Output:- 

Enter value of x= 2

Enter value of y= 3

Enter value of z= 3

Product= 18