1. Chapter: 09
Inheritance
Lecture: 30 & 31
Date: 08.10.2012

2. Inheritance:
Base and Derived Classes
 Inheritance is the
process of creating a
new classes (derived
classes) from existing
classes (based classes).

3. Inheritance:
Base and Derived Classes

4. Inheritance: Advantages
 Permits code reusability
 Reusing existing code saves time and money and
increases a program’s reliability

5. Inheritance: Shapes
Polygon
Rectangle
Triangle

6. No-Inheritance: Shapes
class Rectangle{
Polygon private:
int numVertices;
int xCoord, yCoord;
public:
Rectangle void set(int x, int y, int nV);
Triangle
int area();
};
class Polygon{
private: class Triangle{
int numVertices; private:
int xCoord, yCoord; int numVertices;
int xCoord, yCoord;
public:
public:
void set(int x, int y, int nV);
void set(int x, int y, int nV);
int area();
int area();
}; };

7. Inheritance: Shapes
class Polygon{
Polygon protected:
int numVertices;
float xCoord, yCoord;
public:
void set(int x, int y, int nV);
};
Rectangle
Triangle
class Rectangle : public Polygon{
public:
int area();
};

8. Inheritance: Shapes
class Polygon{
Polygon protected:
int numVertices;
float xCoord, yCoord;
public:
void set(float x, float y, int nV);
};
Rectangle
Triangle
class Triangle : public Polygon{ class Rectangle : public Polygon{
public: public:
int area(); float area();
}; };

9. Inheritance: Syntax
 Syntax:
class DerivedClassName : access-level BaseClassName
where
 access-level specifies the type of derivation
 private by default, or
 Public
 Any class can serve as a base class
 Thus a derived class can also be a base class

10. Inheritance: Syntax
 Syntax:
class DerivedClassName : access-level BaseClassName
Example:
class BaseClass
{
}
class DerivedClass: public BaseClass
{
}

11. Access Specifier without Inheritance

12. Access Specifier with Inheritance

13. Inheritance and Accessibility

14. Overriding member functions
 Member functions in a derived class can have the same
names as in the base class
 When the same function exists in both the base and
derived classes, the function in the derived class will be
executed.
 In order to call a function in the base class use the use the scope resolution
operator, e.g.,
Stack :: push()
Name Scope
Call to a member function
(base class) resolution
in base class

15. Stack Applications
 Memory management
 Tower of Hanoi

16. Stack Applications
 Converting a decimal number to binary

17. Inheritance: Shapes
x
class Point{
Point
y protected:
int x, y;
public:
Circle 3D-Point void set (int a, int b);
x x
};
y y
r z
class Circle : public Point{ class 3D-Point: public Point{
private: private:
double r; int z;
}; };