Defining Derived Classes

In C++ programming, you can define a derived class by simply specifying its relationship with the base class in addition to its detail.

Syntax:

class derived-class-name : visibility-mode base-class-name
{
	//members of derived class
}

Below are some features of defining derived classes

• The required keyword is class 
• The name that is given to the derived class is known as derived-class-name. 
• The name that is given to the base class is known as base-class-name. 
• Colon ‘:’ is used to indicate that the derived class name is derived from the base-class-name 
• The visibility mode is used to specify if the features of the base are privately derived or publicly derived. It is optional, if present, may be either private or public. However, the default visibility mode is private. 

Example:

class Shape
{
protected:
	float width, height;
public:
	void set_data (float a, float b)
	{
		width = a;
		height = b;
	}
};

class Rectangle: public Shape
{
public:
	float area ()
	{
		return (width * height);
	}
};

class Triangle: public Shape
{
public:
	float area ()
	{
		return (width * height / 2);
	}
};

void main ()
{
	Rectangle rect;
	Triangle tri;
	rect.set_data (5,3);
	tri.set_data (2,5);
	cout << rect.area() << endl;
	cout << tri.area() << endl;
	getch();
}

A derived class in C++ inherits all base class methods, except the following:

• The Constructors, the destructors, and the copy constructors of the base class.
• The Overloaded operators of the base class.
• And the friend functions of the base class.