Syntax rules for writing constructor functions

• Its name must be similar as that of the class to which it belongs.
• It is declared with no return type (not even void). However, it will implicitly return a temporary copy of the instance itself that is being formed.
• It cannot be declared static (a function which does not belong to a particular example), cost( in which you cannot make changes).
• It should have public or protected access within the class. Only in very rare circumstances the programmers declare it in private section.

e.g.

class  boxclass

                 {

                  public :

                boxclass ( int x1, int y1, int x2, int y2);

                void disp(void);

                  private :

                                                int x1, y1;

int x2, y2 ;

                 };

boxclass::boxclass(int ax1,int ay1, int ax2, int ay2)

                 {

                                x1 = ax1 ;

                                y1 = ay1 ;

                                x2 = ax2 ;

                                y2 = ay2 ;

       }