C++ Interview Questions

Introduction

You maybe a great programmer who uses C/C++ everyday but if you really want that new job, it maybe a good idea to review the core principles of C/C++ before the interview. I have compiled a list of 10 questions that I feel you should know the answers to if you are applying for any C++ position. At the end of the article, I have also added some links to sites to help you prepare for your interview.

What is the difference between C and C++ ? Would you prefer to use one over the other ?

C is based on structured programming whereas C++ supports the object-oriented programming paradigm.Due to the advantages inherent in object-oriented programs such as modularity and reuse, C++ is preferred. However almost anything that can be built using C++ can also be built using C.

What are the access privileges in C++ ? What is the default access level ?

The access privileges in C++ are private, public and protected. The default access level assigned to members of a class is private. Private members of a class are accessible only within the class and by friends of the class. Protected members are accessible by the class itself and it's sub-classes. Public members of a class can be accessed by anyone.

What is data encapsulation ?

Data Encapsulation is also known as data hiding. The most important advantage of encapsulation is that it lets the programmer create an object and then provide an interface to the object that other objects can use to call the methods provided by the object. The programmer can change the internal workings of an object but this transparent to other interfacing programs as long as the interface remains unchanged.

What is inheritance ?

Inheritance is the process of deriving classes from other classes. In such a case, the sub-class has an 'is-a' relationship with the super class. For e.g. vehicle can be a super-class and car can be a sub-class derived from vehicle. In this case a car is a vehicle. The super class 'is not a' sub-class as the sub-class is more specialized and may contain additional members as compared to the super class. The greatest advantage of inheritance is that it promotes generic design and code reuse.

What is multiple inheritance ? What are it's advantages and disadvantages ?

Multiple Inheritance is the process whereby a sub-class can be derived from more than one super class. The advantage of multiple inheritance is that it allows a class to inherit the functionality of more than one base class thus allowing for modeling of complex relationships. The disadvantage of multiple inheritance is that it can lead to a lot of confusion when two base classes implement a method with the same name.

What is polymorphism?

Polymorphism refers to the ability to have more than one method with the same signature in an inheritance hierarchy. The correct method is invoked at run-time based on the context (object) on which the method is invoked. Polymorphism allows for a generic use of method names while providing specialized implementations for them.

What do the keyword static and const signify ?

When a class member is declared to be of a static type, it means that the member is not an instance variable but a class variable. Such a member is accessed using Classname.Membername (as opposed to Object.Membername). Const is a keyword used in C++ to specify that an object's value cannot be changed.

How is memory allocated/deallocated in C ? How about C++ ?

Memory is allocated in C using malloc() and freed using free(). In C++ the new() operator is used to allocate memory to an object and the delete() operator is used to free the memory taken up by an object.

What is UML ?

UML refers to Unified Modeling Language. It is a language used to model OO problem spaces and solutions.

What is the difference between a shallow copy and a deep copy?

A shallow copy simply creates a new object and inserts in it references to the members of the original object. A deep copy constructs a new object and then creates in it copies of each of the members of the original object.