Constructor in Object Oriented Programming

Constructor in Object Oriented Programming

Q. 1 Define a constructor in Object Oriented Programming.

A constructor is a special member function whose task is to initialize the objects of its class. It is special because its name is same as class name. The constructor is invoked whenever an object of its associated class is created. It is called constructor because it constructs the values of data members of the class. 

For example:

Class A

{ 

// data members

public: 

//This is a constructor of class A and used to initialize the data members of the class

A( ); 

// member functions

};

Q. 2 Define default constructor in Object Oriented Programming. 

In a program if we have a constructor with no arguments then that constructor is called default constructor.

For example:

Class A 

{ 

// data members

int a, b;

Public: 

A( ); 

// member functions

}; 

A :: A( ) //default constructor 

{ 

a=0;

b=0; 

} 

Now the statement, A obj; invokes the default constructor automatically after the declaration of this statement.

Q. 3 Write some special characteristics of constructor in Object Oriented Programming.

1. Constructor should be declared in the public section of the class.

2. Constructor are invoked automatically when the objects of that class are created. 

3. Constructor do not have return types, not even void.

4. Constructor cannot return values. 

5. Constructor cannot be inherited, though a derived class. 

6. Constructor can have default arguments in it.

7. Constructors cannot be virtual function. 

Q. 4 Define parameterized constructor in Object Oriented Programming.

In a program if we have a constructor with arguments then that constructor are called as parameterized constructor. 

For example: 

Class A 

{ 

// data members of class A

int a, b; 

public: 

A(int x, int y) 

{ 

a = x;

b = y; 

} 

To invoke parameterized constructor in class, we must pass the initial values as arguments to the constructor function when an object is declared. This is done in two ways 

1. By calling the constructor explicitly 

A obj = A(1, 2); 

2. By calling the constructor implicitly 

A obj(1, 2); 

Q. 5 Define default argument constructor in Object Oriented Programming. 

In a program if we have a constructor with default arguments then that constructor are called default argument constructor. 

For example:

A(float a, float b = 0); // here the default value of the argument b is 0. 

now the statement A obj(6.0) will assign a = 6.0 and b=0 and A obj(2.3,9.0) will assign a = 2.3 and b=9.0.

Thanks

Mukesh Rajput