The 1-2-3 Of C++ Interview- Common But Essential Questions To Ace Any C++ Interview

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What if you already know C++ programming? Or what if you have mastered the concepts of the C++ programming language by reading the best C++ books?  If yes, then now is the time to showcase your C++ skills in your next job. But wait, you still have an interrogation to clear on C++ programming before you get your dream job. No worries! We are here with an exclusive list of C++ Interview Questions that will help you clear your next job interview.

What Are The C++ Interview Questions?

Q1. How C is different from C++?

-> C++ might be created on C programming but altogether both have notable differences.

  1. C++ is basically a superset of C language. The majority of the C programs can work well in C++.
  2. C++ is an Object-Oriented & procedural programming language, but C is just about procedural programming.
  3. As C++ is object-oriented programming, it has additional features like templates, virtual functions, function overloading, friend functions & templates that are absent in C.
  4. With C programming, exceptional handling can only be done in traditional if-else style while C++ supports exceptional handling at the language level.
  5. C doesn’t support references and C++ supports it.
  6. C++ majorly uses streams for performing input or output where cout is standard output stream and cin is a standard input stream. Whereas, scan() & printf() are used respectively for input or output in C programming.

Of course, there are many more differences but these are the major ones.

Q2. How will you explain the difference between references and pointers?

-> References & pointers in C++ have few similarities like they can be used for saving copying of big objects to get efficiency gain when these objects are passed as arguments to functions or even returned from functions. Both of them can also change local variables of one function inside different unction. Despite these, they have several differences. 

  1. Pointers are more powerful than references.
  2. Once pointers are created, it can be made to reference another object afterward, however, this is not the case with pointers.
  3. Pointers can be made NULL whereas, references can’t be NULL.
  4. It is important to initialized reference when declared while in the case of pointers, there are not any such restrictions.

Because of these restrictions, C++ references are not used or using data structures like Tree, Linked List & others. However, when it comes to Java programming, there are not any such restrictions for references and because of this, references are more powerful. You don’t need pointers in Java.

Apart from all the limitations, references are more easier and safer to use than pointers. References don’t require and dereferencing operator and can be used as a normal variable. 

Q3. How can you explain virtual functions – Write an example?

-> You can use virtual functions with inheritance. They are called as per the type of the object pointed or referred instead of a type of pointer or reference. In simple words, we can say that virtual functions are resolved late at runtime. You can use a virtual keyboard for making any function virtual.

Below are the essential things that are required to use virtual functions in C++.

  1. Base class with a derived class.
  2. A function having the same name in the derived class and a base class.
  3. Any pointer (or reference) of base class type pointing (or referring) to a derived class object.

For instance, in the below program, bp is a pointer of type Base, but a call to bp->show() calls show() function of Derived class because bp points to an object of Derived class.

#include<iostream> 
using namespace std; 

class Base { 
public: 
    virtual void show() { cout<<" In Base \n"; } 
}; 

class Derived: public Base { 
public: 
    void show() { cout<<"In Derived \n"; } 
}; 

int main(void) { 
    Base *bp = new Derived;	 
    bp->show(); // RUN-TIME POLYMORPHISM 
    return 0; 
}

Output:

In Derived

Q4. What do you know about ‘this’ pointer?

It is passed as a hidden argument to all nonstatic member function calls. ‘this’ pointer is available within the body of all nonstatic functions as a local variable. It also holds the memory address of the current object and is a constant pointer. It is not available in the static member functions. It is because the static member function can be called without any object or with the class name.

Q5. What are the main differences between Java and C++? 

There are some notable differences between Java & C++. These are as follows:

  1. In Java programming, you can find garbage collection, and C++ includes destructors that are automatically invoked if the object is destroyed.
  2. Unlike the C++ language, Java doesn’t support any templates, structures, pointers, operator overloading, unions, and others.
  3. Java has a thread class that you inherit for creating a new thread while C++ doesn’t have any built-in support for threads.
  4. In Java, there is not any ‘goto’.
  5. Java only has method overloading, but in C++, there are operator overloading as well as method overloading.
  6. Java does not support multiple inheritances using class, but C++ supports multiple inheritances using classes.
  7. Java is platform-independent and interpreted programming language but C++ isn’t. 

Q6. What do you know about C++ access specifiers?

-> These are used for defining how you can access members like variables or functions outside the class. There are 3 options for it.

  1. Public: Any members that are declared as public can be access from anywhere.
  2. Private: Members that are declared as private can only be accessible from the same class. These cannot be accessed from outside the class they are declared and even child classes are not allowed for accessing the parent members.
  3. Protected: Protected members can only be accessed through class or its child classes.

Q7. What are the major C++ features?

-> Some of the important features of C++ programming are as follows:

  1. Object: these are basic runtime entities in any object-oriented system. These can also be instances of a class.
  2. Class: You can call t as a blueprint of data and functions or methods. It doesn’t take any space.
  3. Encapsulation & Data Abstraction: Combining or wrapping the data and function into a single unit is called encapsulation. Since data cannot be accessed through the outside world, it can only be accessed through functions that are wrapping in the class. Insulating the data from its direct access by the program is called information hiding or data hiding.
  4. Data Abstraction: It helps in providing only the required information to the outside world and hides all the details regarding implementation. The benefit of the data abstraction is that we can change implementation at any point. This will not affect any users of the Complex class since the method interference is the same. 
  5. Polymorphism: In simple terms, it means the ability to take more than one form. In different instances, an operation may exhibit different behaviors. These behaviors depend upon the types of data used in operation.
  6. Inheritance: It is one of the processes which allows objects of one class to acquire the property of objects from a different class. Inheritance supports the concepts of hierarchical classification and also provides reusability. Because of this, you can add extra features to an existing class without any need for modification.
  7. Dynamic Binding: In this, your code can be executed in response to the function call. It is decided at runtime.
  8. Message Passing: Objects have the ability to communicate with each other by receiving or sending information to one another. For an object, any message is generally a request for execution of a procedure. Therefore, it will invoke a function in the receiving object that then generates the desired results. It involves specifying the function name, object name, and the information which needs to be sent.

Q8. What are the main differences between Structure & class in C++?

-> In C++ programming language, the C++ structure is similar to a class but has a few differences like:

  1. Members of a struct are public by default and members of a class are private by default.
  2. The default access-specifier for a base class/struct remains public while deriving a struct from a class/struct. Whereas, default access specifier is private when you are deriving a class. 

Q9. How will you explain Inline Functions?

-> Or reducing the function call overhead, C++ language offers an inline function. It is basically a function that can be expanded when it is called. When we call the inline function, the whole code of the inline function gets substituted or inserted at the point of an inline function call. At compile time, this substitution is performed by the C++ compiler. If an inline function is small, it may increase efficiency significantly.

For defining the inline function, the syntax is as following:

inline return-type function-name(parameters)

inline return-type function-name(parameters)

{

// function code


}

Don’t forget that inlining is not a command but only a request to the compiler. The compiler can ignore the request for inlining.

Q10. What Is Inheritance?

-> There is always a certain amount in common with each other when it comes to different kinds of objects. Despite this, each object defines extra features that make them unique in their own ways. In object-oriented programming, you can use classes for inheriting commonly used behavior and state from other classes.

Also Read: An In-Depth Guide On Inheritance in C++ Programming

Q11. Define Static Member?

-> In C++ programming language, static is a keyword that is used to give special characteristics to any element. Static elements are usually allocated storage in static storage area & they have a scope till the program lasts.

Some interesting facts of static member functions in C++ language are as follows:

  1. A static member function cannot be virtual
  2. They don’t have this pointer
  3. This type of function cannot be declared volatile, const, or const volatile.
  4. You can’t overload member function declarations with the name parameter-type-list and the same name if any of them is a static member function declaration.

Also Read: 

So, these were some of the most common but important C++ interview questions that you can go through to clear your next interview.

If you are looking to brush up your C++ programming, then you can read “C++ Books- 13 Proven Books To Get Into C++ Programming“. And if you are looking for a comprehensive tutorial to understand & answer all the complexities of C++, then you can start off with “Learn By Example C++ Programming 75 Solved Problems“.

In case, if you are looking for learning C++ from scratch or to use C++ IDEs in an interactive way, then you can choose “C++ For Absolute Beginners: The Starter Guide” for a complete understanding.

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