Default Constructor in C++ Programming

Constructors are special function named after the class and without a return type, and are used to construct objects. Constructors, like function, can take input parameters. Constructors are used to initialize objects.

Constructors are different from function:

Constructors must be named the same as the class name.
Constructor is automatically called when object(instance of class) is created.
Constructors do not have a return type

Types of constructor :

Default constructor
Parametrized constructor
Copy constructor
Constructor Overloading

The program defines a class named math which has private data members a, b, and c, and a public member function add(). The math() function is a default constructor that initializes the private data members a and b to 0.

The add() function calculates the sum of the private data members a and b, and stores it in the private data member c. It then outputs the total sum to the standard output using cout.

In the main() function, an object of the math class is created using the default constructor. The add() member function of themath class is then called on the object to calculate and display the sum of a and b.

Overall, this program provides an example of using a default constructor in C++ to initialize the private data members of a class object. The program demonstrates the use of a default constructor as a special member function of a class which is executed automatically whenever an object of the class is created.

Source Code

#include<iostream>
using namespace std;
/*
    Default Constructor
    Parameterized Constructor
    Copy Constructor
*/
//Default Constructor in C++ Programming
/*
 
A constructor in C++ is a special ‘MEMBER FUNCTION’
having the same name as that of its class which is
used to initialize some valid values to the data members
of an object. It is executed automatically whenever an
object of a class is created.
 
*/
 
class math
{
private:
    int a,b,c;
public:
    math()
    {
        a=0;
        b=0;
    }
    void add()
    {
        c=a+b;
        cout<<"Total : "<<c;
    }
};
int main()
{
    math o;
    o.add();
    return 0;
}

Output

Total : 0

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