Constructor

In C++, a class constructor is a special member function of a class that is executed whenever a new object of that class is created. They have the exact same name as the class. 

Constructor in C++ does not have any return type at all, not even void. However, they can be very useful in setting initial values for certain member variables.  

Syntax:

class_name () 

{ 

Constructor Definition 

}

Example:

#include <iostream>

class Line
{
 public:
 void setLength( double len );
 double getLength( void );
 Line(); // This is the constructor

private:
 double length;
};
// Member functions definitions including constructor
Line::Line(void)
{
 cout << "Object is being created" << endl;
}
void Line::setLength( double len )
{
 length = len;
}
double Line::getLength( void )
{
 return length;
}
// Main function for the program
void main( )
{
 Line line;
 // set line length
 line.setLength(6.0);
 cout << "Length of line : " << line.getLength() <<endl;
 getch();
}