1.      Program to demonstrate inheritance and polymorphism using virtual functions.

1. #include <iostream.h>

2. #include <graphics.h>

3. #include<conio.h>

4.  

5. class Shape {

6. public:

7.     virtual void draw() = 0;

8. };

9.  

10. class Line : public Shape {

11. public:

12.     void draw() {

13.                 cout << "Drawing a Line" << endl;

14.                 // Draw a line

15.                 line(100, 100, 100, 200);

16.  

17.     }

18. };

19.  

20. class Circle : public Shape {

21. public:

22.     void draw() {

23.                 cout << "Drawing a circle" << endl;

24.                 // Draw a circle

25.                 circle(200, 200, 50);

26.  

27.     }

28. };

29.  

30. class Rectangle : public Shape {

31. public:

32.     void draw() {

33.                 cout << "Drawing a rectangle" << endl;

34.                 // Draw a rectangle

35.                 rectangle(100, 250, 300, 350);

36.  

37.     }

38. };

39.  

40. int main() {

41.     int gd = DETECT, gm;

42.  

43.     initgraph(&gd, &gm, "C:/TURBOC3/BGI");

44.  

45.  

46.     Shape *shapePtr;

47.     Line line;

48.     Circle circle;

49.     Rectangle rectangle;

50.  

51.     shapePtr = &line;

52.     shapePtr->draw();

53.     getch();

54.     shapePtr = &circle;

55.     shapePtr->draw();

56.     getch();

57.     shapePtr = &rectangle;

58.     shapePtr->draw();

59.     getch();

60.     closegraph();

61.     return 0;

63. }