Class and Constructor

What is Class?

A class is like a blueprint for an object. It is a user defined data type, which holds its own data members and member functions, which can be accessed and used by creating an instance of that class.

What is Constructor?

A constructor is a member function of a class which initializes objects of a class. In C++, Constructor is automatically called when object(instance of class) create. It is special member function of the class.

How constructors are different from a normal member function?

A constructor is different from normal functions in following ways:

  • Constructor has same name as the class itself
  • Constructors don’t have return type
  • A constructor is automatically called when an object is created.
  • If we do not specify a constructor, C++ compiler generates a default constructor for us (expects no parameters and has an empty body).

Note: Class and Constructor name must be same.

//simple code
using namespace std;
class Rectangle
   private : int length,breadth;
   public :
         Rectangle(){                                    //constructor
                          Rectangle(int l,int b)                              //function overloading
                                   int area();                                         //accessor
                                    int perimeter();                               //accesor
                        int getLength(){                                  //accessor
                               return length;
                     void setLength(int l){                                    //mutator
                            ~Rectangle();                                //destructor
       Rectangle :: area()
                  return length * breadth;
int Rectangle :: perimeter()
return 2* (length + breadth);
Rectangle :: Rectangle(int l,int b)
length =l;
Rectangle :: ~Rectangle()
int main()
Rectangle r(10,5);

Once’s the main function end destructor will automatically call because object is going outside scope.


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