C++: calling base class constructors

	#include <iostream>
	#include <stdio.h>
	using namespace std;
	// Base class
	class Shape
	{
	public:
	void setWidth(int w)
	{
	width = w;
	}
	void setHeight(int h)
	{
	height = h;
	}
	Shape()
	{
	printf("creating shape \n");
	}
	Shape(int h,int w)
	{
	height = h;
	width = w;
	printf("creatig shape with attributes\n");
	}
	protected:
	int width;
	int height;
	};
	// Derived class
	class Rectangle: public Shape
	{
	public:
	int getArea()
	{
	return (width * height);
	}
	Rectangle()
	{
	printf("creating rectangle \n");
	}
	Rectangle(int h,int w)
	{
	printf("creating rectangle with attributes \n");
	height = h;
	width = w;
	}
	};
	int main(void)
	{
	Rectangle Rect;
	Rect.setWidth(5);
	Rect.setHeight(7);
	Rectangle *square = new Rectangle(5,5);
	// Print the area of the object.
	cout << "Total area: " << Rect.getArea() << endl;
	return 0;
	}
	Output:
	creating shape
	creating rectangle
	creating shape
	creating rectangle with attributes
	Total area: 35

view raw gistfile1.cpp hosted with ❤ by GitHub

The default class constructor is called unless you explicitly call another constructor in the derived class. the language specifies this.

Rectangle(int h,int w):
   Shape(h,w)
  {...}