22316 Object-Oriented Programming using C++ External Oral / Viva Practice Questions with Answers
Basic Questions
1. What is the difference between OOP and SOP?
2. What is Object Oriented Programming?
Object-Oriented
Programming(OOPs) is a type of programming that is based on objects rather than
just functions and procedures. Individual objects are grouped into classes.
OOPs implements real-world entities like inheritance, polymorphism, hiding, etc
into programming. It also allows binding data and code together.
- OOPs
allows clarity in programming thereby allowing simplicity in solving
complex problems
- Code
can be reused through inheritance thereby reducing redundancy
- Data
and code are bound together by encapsulation
- OOPs
allows data hiding, therefore, private data is kept confidential
- Problems
can be divided into different parts making it simple to solve
- The
concept of polymorphism gives flexibility to the program by allowing the
entities to have multiple forms
4. What are the main features of OOPs?
To know more about
OOPs in JAVA, Python, and C++ you can go through the following blogs:
Classes and Objects Questions
An object is a
real-world entity which is the basic unit of OOPs for example chair, cat, dog,
etc. Different objects have different states or attributes, and behaviours.
6. What is a class?
A class is a
prototype that consists of objects in different states and with different
behaviors. It has a number of methods that are common the objects present
within that class.
7. What is the difference between a class and a
structure?
Class: User-defined
blueprint from which objects are created. It consists of methods or set of
instructions that are to be performed on the objects.
Structure: A structure is
basically a user-defined collection of variables which are of different data
types.
8. Can you call the base class method without
creating an instance?
Yes, you can call
the base class without instantiating it if:
- It
is a static method
- The
base class is inherited by some other subclass
9. What is the difference between a class and an
object?
|
Object |
Class |
|
A real-world
entity which is an instance of a class |
A class is
basically a template or a blueprint within which objects can be created |
|
An object acts
like a variable of the class |
Binds methods
and data together into a single unit |
|
An object is a
physical entity |
|
|
Objects take memory
space when they are created |
A class does not
take memory space when created |
|
Objects can be
declared as and when required |
Classes are
declared just once |
Inheritance Questions
10. What is inheritance?
Inheritance is a
feature of OOPs which allows classes inherit common properties from other
classes. For example, if there is a class such as ‘vehicle’, other classes like
‘car’, ‘bike’, etc can inherit common properties from the vehicle class. This
property helps you get rid of redundant code thereby reducing the overall size
of the code.
11. What are the different types of inheritance?
- Single
inheritance
- Multiple inheritance
- Multilevel inheritance
- Hierarchical inheritance
- Hybrid
inheritance
12. What is the difference between multiple and multilevel
inheritance?
|
Multiple Inheritance |
Multilevel Inheritance |
|
Multiple
inheritance comes into picture when a class inherits more than one base class |
Multilevel
inheritance means a class inherits from another class which itself is a
subclass of some other base class |
|
Example: A class
defining a child inherits from two base classes Mother and Father |
Example: A class
describing a sports car will inherit from a base class Car which inturn
inherits another class Vehicle |
13. What is hybrid inheritance?
Hybrid inheritance
is a combination of multiple and multi-level inheritance.
14. What is hierarchical inheritance?
Hierarchical
inheritance refers to inheritance where one base class has more than one
subclasses. For example, the vehicle class can have ‘car’, ‘bike’, etc as its
subclasses.
15. What are the limitations of inheritance?
- Increases
the time and effort required to execute a program as it requires jumping
back and forth between different classes
- The
parent class and the child class get tightly coupled
- Any
modifications to the program would require changes both in the parent as
well as the child class
- Needs
careful implementation else would lead to incorrect results
A superclass or
base class is a class that acts as a parent to some other class or classes. For
example, the Vehicle class is a superclass of class Car.
17. What is a subclass?
A class that
inherits from another class is called the subclass. For example, the class Car
is a subclass or a derived of Vehicle class.
Polymorphism Questions
18. What is
polymorphism?
Polymorphism
refers to the ability to exist in multiple forms. Multiple definitions can be
given to a single interface. For example, if you have a class named Vehicle, it
can have a method named speed but you cannot define it because different
vehicles have different speed. This method will be defined in the subclasses
with different definitions for different vehicles.
19. What is static polymorphism?
Static
polymorphism (static binding) is a kind of polymorphism that occurs at compile
time. An example of compile-time polymorphism is method overloading.
20. What is dynamic polymorphism?
Runtime
polymorphism or dynamic polymorphism (dynamic binding) is a type of
polymorphism which is resolved during runtime. An example of runtime
polymorphism is method overriding.
21. What is method overloading?
Method overloading
is a feature of OOPs which makes it possible to give the same name to more than
one methods within a class if the arguments passed differ.
22. What is method overriding?
Method overriding
is a feature of OOPs by which the child class or the subclass can redefine
methods present in the base class or parent class. Here, the method that is
overridden has the same name as well as the signature meaning the arguments
passed and the return type.
23. What is operator overloading?
Operator
overloading refers to implementing operators using user-defined types based on
the arguments passed along with it.
24. Differentiate between overloading and
overriding.
|
Overloading |
Overriding |
|
Two or more
methods having the same name but different parameters or signature |
Child class
redefining methods present in the base class with the same parameters/
signature |
|
Resolved during
compile-time |
Resolved during
runtime |
Encapsulation Questions
25. What is encapsulation?
Encapsulation
refers to binding the data and the code that works on that together in a single
unit. For example, a class. Encapsulation also allows data-hiding as the data
specified in one class is hidden from other classes.
26. What are ‘access specifiers’?
Access specifiers or access modifiers are keywords that
determine the accessibility of methods, classes, etc in OOPs. These access
specifiers allow the implementation of encapsulation. The most common access
specifiers are public, private and protected. However, there are a few more
which are specific to the programming languages.
27. What is the difference between public, private
and protected access modifiers?
|
Name |
Accessibility from own class |
Accessibility from derived class |
Accessibility from world |
|
Public |
Yes |
Yes |
Yes |
|
Private |
Yes |
No |
No |
|
Protected |
Yes |
Yes |
No |
Data abstraction
28. What is data abstraction?
Data abstraction
is a very important feature of OOPs that allows displaying only the important
information and hiding the implementation details. For example, while riding a
bike, you know that if you raise the accelerator, the speed will increase, but
you don’t know how it actually happens. This is data abstraction as the implementation
details are hidden from the rider.
29. How to achieve data abstraction?
Data abstraction
can be achieved through:
- Abstract
class
- Abstract
method
30. What is an abstract class?
An abstract class
is a class that consists of abstract methods. These methods are basically
declared but not defined. If these methods are to be used in some subclass,
they need to be exclusively defined in the subclass.
31. Can you create an instance of an abstract
class?
No. Instances of
an abstract class cannot be created because it does not have a complete
implementation. However, instances of subclass inheriting the abstract class
can be created.
32. What is an interface?
It is a concept of
OOPs that allows you to declare methods without defining them. Interfaces,
unlike classes, are not blueprints because they do not contain detailed
instructions or actions to be performed. Any class that implements an interface
defines the methods of the interface.
33. Differentiate between data abstraction and
encapsulation.
|
Data abstraction |
Encapsulation |
|
Solves the problem
at the design level |
Solves the
problem at the implementation level |
|
Allows showing
important aspects while hiding implementation details |
Binds code and
data together into a single unit and hides it from the world |
Methods and Functions questions
34. What are virtual functions?
Virtual functions
are functions that are present in the parent class and are overridden by the
subclass. These functions are used to achieve runtime polymorphism.
35. What are pure virtual functions?
Pure virtual
functions or abstract functions are functions that are
only declared in the base class. This means that they do not contain any
definition in the base class and need to be redefined in the subclass.
36. What is a constructor?
A constructor is a
special type of method that has the same name as the class and is used to
initialize objects of that class.
37. What is a destructor?
A destructor is a
method that is automatically invoked when an object is destroyed. The
destructor also recovers the heap space that was allocated to the destroyed
object, closes the files and database connections of the object, etc.
38. Types of constructors
Types of constructors differ from
language to language. However, all the possible constructors are:
- Default
constructor
- Parameterized
constructor
- Copy
constructor
- Static
constructor
- Private
constructor
39. What is a copy constructor?
A copy constructor creates objects by
copying variables from another object of the same class. The main aim of a copy
constructor is to create a new object from an existing one.
40. What is the use of ‘finalize’?
Finalize as an
object method used to free up unmanaged resources and cleanup before Garbage
Collection(GC). It performs memory management tasks.
41. What is Garbage Collection(GC)?
GC is an implementation of automatic memory management. The Garbage collector frees up space occupied by objects that are no longer in existence.
42. Differentiate between a class and a method.
|
Class |
Method |
|
A class is
basically a template that binds the code and data together into a single
unit. Classes consist of methods, variables, etc |
Callable set of
instructions also called a procedure or function that are to be performed on
the given data |
43. Differentiate between an abstract class and an interface?
|
Basis for comparison |
Abstract Class |
Interface |
|
Methods |
Can have
abstract as well as other methods |
Only abstract
methods |
|
Final Variables |
May contain
final and non-final variables |
Variables
declared are final by default |
|
Accessibility of Data Members |
Can be private,
public, etc |
Public by
default |
|
Implementation |
Can provide the
implementation of an interface |
Cannot provide
the implementation of an abstract class |
44. What is a final variable?
A variable whose
value does not change. It always refers to the same object by the property of
non-transversity.
Exception Handling Questions
45. What is an exception?
An exception is a
kind of notification that interrupts the normal execution of a program.
Exceptions provide a pattern to the error and transfer the error to the
exception handler to resolve it. The state of the program is saved as soon as
an exception is raised.
46. What is exception handling?
Exception handling
in Object-Oriented Programming is a very important concept that is used to
manage errors. An exception handler allows errors to be thrown and caught and
implements a centralized mechanism to resolve them.
47. What is the difference between an error and an
exception?
|
Error |
Exception |
|
Errors are
problems that should not be encountered by applications |
Conditions that
an application might try to catch |
48. What is a try/ catch block?
A try/ catch block is used to handle exceptions.
The try block defines a set of statements that may lead to an error. The catch
block basically catches the exception.
49. What is a finally block?
A finally block
consists of code that is used to execute important code such as closing a
connection, etc. This block executes when the try block exits. It also makes
sure that finally block executes even in case some unexpected exception is
encountered.
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