CBSE Class 12 Computer Science C++: Constructor and Destructor NCERT Solutions

Solution: The key characteristics of a constructor function in C++ are:

1. No Return Type: A constructor function does not have any return type, not even void.
2. Same Name as Class: The name of the constructor function must be identical to the name of the class it belongs to.
3. Automatic Invocation: A constructor is automatically called by the system when an object of the class is created.
4. Default Constructor Invocation: If a class does not explicitly declare any constructor, the compiler automatically provides a default constructor, which is then invoked when objects are created.

Solution: A copy constructor is a special type of constructor in C++ that is used to create a new object and initialize it with the values of an existing object of the same class. It takes a reference to an object of the same class as its parameter.

Here is an example illustrating the definition and usage of a copy constructor:

class point {

int x;

public:

point () { x = 0; } // Default constructor

point (Point &p) { x = p.x; } // Copy constructor }; void main () {

point p1; // Default constructor is called, p1.x becomes 0

point p2 (p1); // Copy constructor is called, p2.x is initialized with p1.x (which is 0)

// Alternatively, the following also calls the copy constructor:

// point p3 = p1; } In this example, `point(Point &p)` is the copy constructor. When `point p2(p1);` or `point p3 = p1;` is executed, the copy constructor is invoked to create `p2` (or `p3`) as a copy of `p1`.

(i) Which OOP concept does Function 1 and Function 2 implement? Explain.

Function 1 and Function 2 implement the OOP concept of Constructor Overloading, which is a form of Polymorphism. This is because multiple constructor functions are defined within the same class scope, each having a different parameter list. Function 1 is a Default Constructor as it takes no arguments. Function 2 is a Parameterized Constructor as it accepts arguments (`int Rno` and `char candname[]`) to initialize the object's data members.

(ii) What is Function 3 called? When will it be invoked?

Function 3, `~Exam()`, is called a Destructor. It is automatically invoked when an object of the `Exam` class goes out of scope (e.g., at the end of the block or function where it was declared) or when the memory allocated for the object is explicitly deallocated using `delete`.