The document provides information about constructors and destructors in C++. It defines constructors and destructors, explains when they are invoked and their purposes. It discusses the differences and similarities between constructors and destructors. It also provides examples of defining and calling different types of functions like default, parameterized, and copy constructors as well as destructors. The document aims to help students understand constructors and destructors which are important concepts for exams.

2. GET 100% MARKS IN
COMPUTER SCIENCE
CONSTRUCTOR
AND DESTRUCTOR

3. IN THIS PART 3 TYPE OF QUESTIONS CAN BE
FORMED IN YOUR EXAM
1. Theory Question (Basically definition or difference or similarities).
2. To identify the type of function (constructor, destructor, copy constructor
etc.)
3. To write calling statement for a particular function.

4. IMPORTANT THEORY QUESTIONS
Q.1Define Constructor ?when it will be invoked and work/purpose
of constructor ?
Ans. A constructor is a member function with same name as of
class. Which is invoked automatically when an object comes in
scope. And its work/Purpose is to allocate space to object and to
initialize the data members with legal initial values.

5. IMPORTANT THEORY QUESTIONS
Q.2 Define Destructor ?when it will be invoked and work/purpose
of constructor ?
Ans. A Destructor is a member function with same name as of
class but precedes with a tilde(~) Symbol. Which is invoked
automatically when an object goes out of scope. And its
work/Purpose is to de allocate space & resources allocated during
construction process.

6. Q.3 DIFFERENCE BETWEEN CONSTRUCTOR & DESTRUCTOR?
CONSTRUCTOR
• It is declared with same name as of
class.
• Works to allocated space and
resources to objects.
• Called automatically when an object
comes in scope.
• Can be overloaded.
• Can contain arguments.
DESTRUCTOR
• Declared with same name as of class but
precedes with a tilde(~ symbol)
• Works to deallocate space and resources
allocated during constuction.
• Called automatically when an object goes
out of scope.
• Can’t be overloaded.
• Can’t contain arguments.
IMPORTANT THEORY QUESTIONS

7. Q.4 SIMILARITIES BETWEEN CONSTRUCTOR & DESTRUCTOR?
• Both are declared with same name as of class
• Both will be called automatically by compiler.
• Doesn’t contain any return type.
• If we don’t declare a constructor or destructor for a class compiler will by
default provide one to the class.
IMPORTANT THEORY QUESTIONS

8. Q.5 DEFINE COPY CONSTRUCTOR? WHEN IT WILL BE INVOKED?
Q.6 DEFINE DEFAULT CONSTRUCTOR?
Q.7 DEFINE PARAMETERIZED CONSTRUCTOR?
Q.8 DIFFERENCE BETWEEN EXPLICIT & IMPLICIT
CONSTRUCTOR CALLS?
IMPORTANT THEORY QUESTIONS

9. TO IDENTIFY THE TYPE OF FUNCTION
Constructor
Class X()
{
X();
X(int a, int b);
};
Destructor
Class X()
{
~X();
};
Copy Constructor
Class X()
{
X(X &obj);
};

10. TO IDENTIFY & WRITE CALLING STATEMENT FOR A
PARTICULAR FUNCTION
Class XYZ
{
XYZ(); //FUNCTION1
XYZ(int a,int b); //FUNCTION 2
XYZ(XYZ & obj); //function 3
Void show(); //function 4
~XYZ(); //Function 5
};
ANS.
FUCNTION 1 is a default Constructor
XYZ obj;
FUNCTION 2 is an argumented constructor
XYZ obj2(10,20);
FUNCTION 3 is a copy constructor
XYZ obj3=obj2;
Or
XYZ obj4(obj1);
FUNCTION 4 is a member function
Obj4.show();
FUNCTION 5 is a destructor will be called automatically
when an object goes out of scope
Q. Which oops concept is represented by
function1,function 2 and function 3 together
Ans. Constructor overloading or polymorphism
EXAMPLE

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