C and C++ are two of the most prominent and oldest programming languages in the world of software development that are widely used for a variety of applications, and questions from these two languages are still asked by companies in technical interviews.
If You are looking for the best C Cpp interview questions to excel in your next technical interview? This article has everything you need to prepare, with a carefully selected list of questions prepared for both freshers and experienced professionals. Whether you’re just starting out or have years of experience, these questions will help you shine in your interview. Learning these C Cpp Interview questions will boost your confidence and increase your chances of success.
What Is C?
C is a general-purpose programming language that was developed in the early 1970s by Dennis Ritchie at Bell Labs. It has become one of the most widely used programming languages of all time, particularly known for its efficiency, performance, and control over system resources. Below are some key features and characteristics of the C programming language that makes it popular among computer programmers:
Key Features Of C Language
- Simple and Easy to Understand:
C is one of the oldest programming languages and is known for its simplicity and clear syntax. It forms the foundation for many modern programming languages, making it an excellent starting point for beginners.
- Portability:
C is highly adaptable to different platforms and systems, meaning code written in C can be easily transferred and run on various platforms with minimal changes. This characteristic makes C a machine-independent language, which is crucial for developing cross-platform applications.
- Procedural Language:
C uses a structured approach to programming, breaking down code into small, manageable blocks or functions. This procedural nature helps in organizing code effectively, making it easier to understand, debug, and maintain.
- Case Sensitive:
C is case sensitive, meaning it differentiates between uppercase and lowercase letters. For example, variable names ‘C’ and ‘c’ would be treated as distinct identifiers.
- Dynamic Memory Allocation:
C supports dynamic memory allocation, allowing programmers to allocate memory at runtime using functions such as malloc(), calloc(), realloc(), and free().
This feature provides flexibility in managing memory, especially when the required memory size cannot be determined priorly.
- Rich Library:
C provides a comprehensive standard library with numerous built-in functions for handling tasks like input/output operations, string manipulation, and mathematical computations. This rich library support simplifies the coding process and enhances productivity.
- Speed and Efficiency:
C is known for its fast execution speed, as it is a compiled language. Unlike interpreted languages such as Python or Java, C code is directly converted into machine code by the compiler, resulting in faster performance.
What Is C++?
C++ is a powerful, high-performance programming language that supports various programming concepts, including procedural, object-oriented, and generic programming. Developed at Bell Labs in the early 1980s as an enhanced version of the C programming language, C++ has since evolved a lot to provide a wide range of features, making it one of the most versatile and widely used languages in the software development industry.
Key features of C++
Below are some of the key features of the C++ programming language, that make it a popular choice among developers and programmers.
- Object-Oriented Programming (OOP):
- Classes and Objects: C++ supports classes and objects, allowing developers to model real-world entities with attributes and behaviors.
- Inheritance: C++ enables the creation of new classes based on existing ones, promoting code reuse and the creation of hierarchical class structures.
- Polymorphism: Through function overloading and overriding, C++ allows the same function name to operate differently based on the context, enhancing flexibility and code maintainability.
- Encapsulation: C++ also ensures that the internal state of an object is hidden from the outside world, exposing only what is necessary through public interfaces.
- Generic Programming:
C++ allows functions and classes to operate with generic types, enabling code reuse for different data types without sacrificing type safety or performance.
- Low-Level Manipulation:
C++ supports pointer arithmetic and direct memory manipulation, which is critical for systems programming and performance.
- Performance:
C++ is specially designed for performance and efficiency. Programs written in C++ tends to be faster because the language gives control over system resources and memory management.
- Memory Management:
Through new and delete operators, C++ allows explicit allocation and deallocation of memory, which makes the program smooth and fast preventing memory leaks.
- Exception Handling:
C++ provides a robust mechanism for error detection and handling, using try, catch, and throw blocks methods, making it easier to write reliable and maintainable code.
- Multi-Platform Language:
C++ supports procedural programming, object-oriented programming, functional programming, and generic programming, making it a versatile choice for different types of applications.
- Compatibility with C:
Being a superset of C, C++ supports most C features and allows for seamless integration with C code, facilitating a smooth transition for C developers.
C Cpp Interview Questions
We have listed the top 20 C Cpp Interview Questions with Explained Answers, learning these 20 C Cpp Interview questions will help you in clearing your technical interview.
These C Cpp Interview questions written below are carefully selected by experts after analyzing past trends and covering fundamental concepts in C and C++ programming, helping you prepare effectively for your next interview.
- What is the difference between C and C++?
Ans) C is a procedural programming language that focuses on functions and the sequence of steps to solve a problem. It lacks features like classes and objects, making it more linear and function-driven.
C++, on the other hand, is an extended version of C that introduces object-oriented programming (OOP). This means C++ supports classes and objects, which help in organizing code into reusable and modular sections. It allows for concepts like inheritance, polymorphism, and encapsulation, making it more flexible for larger, complex applications.
- What are pointers in C?
Ans) Pointers are variables that store the memory address of another variable. They are powerful because they enable direct manipulation of memory and efficient handling of arrays and dynamic memory allocation. For instance, instead of copying large data structures, you can use pointers to access and modify them directly. However, improper use of pointers can lead to errors like segmentation faults or memory leaks.
- Explain “pass by value” and “pass by reference.”
Ans) “Pass by value” means that when a variable is passed to a function, a copy of the variable is made. Changes to this copy inside the function do not affect the original variable. For example, if you pass an integer to a function and change its value within the function, the original integer remains unchanged.
“Pass by reference” means passing the actual variable itself, not a copy. In C++, this is done using pointers or references. Changes made to the variable within the function affect the original variable. This method is useful for modifying the original data and is more efficient for large data structures.
- What are classes and objects in C++?
Ans) A class is a blueprint for creating objects. It defines attributes and methods that an object created from the class can have. For example, a ‘Car’ class might have attributes like ‘color’ and ‘model’, and methods like ‘drive()’ and ‘stop()’.
An object is an instance of a class, representing a specific example of the class. For example, ‘Car myCar’ creates an object ‘myCar’ from the ‘Car’ class. Each object has its own set of data, distinct from other objects of the same class.
- What is a constructor in C++?
Ans) A constructor is a special member function of a class that is executed whenever a new object of that class is created. Its primary purpose is to initialize the object’s attributes. Constructors have the same name as the class and do not have a return type. For example, in a ‘Car’ class, a constructor might set initial values for ‘color’ and ‘model’ when a new `Car` object is created.
- What is inheritance in C++?
Ans) Inheritance is a property that allows a derived class to inherit attributes and methods from base class. This means the derived class automatically includes the properties and behaviors of the base class, but it can also have additional attributes and methods.
For instance, if ‘Vehicle’ is a base class with methods like ‘start()’ and ‘stop()’, a derived class ‘Car’ can inherit these two methods and can even add new ones in itself like ‘openSunroof()’.
- What is polymorphism in C++?
Ans) Polymorphism means many-form, it is basically the ability of having different classes with the same name of the same class and the specific form is determined by the exact nature of the situation.
- What are virtual functions in C++?
Ans) Virtual functions are member functions in a base class that can be overridden in a derived class. They are declared using the keyword ‘virtual’. When you use a base class pointer to point to a derived class object and call a virtual function, the derived class’s version of the function is executed. This enables dynamic binding, where the call to the function is resolved at runtime, allowing for more flexible and reusable code.
- What is the difference between “new” and “malloc” in C++?
Ans) Both “new” and “malloc” are used for dynamic memory allocation, but they differ in functionality and usage. “new” allocates memory and also calls the constructor to initialize the object, while “malloc” only allocates memory and does not initialize it.
Additionally, “new” returns a pointer of the appropriate type, whereas “malloc” returns a void pointer and requires explicit casting. In C++, it is recommended to use “new” because it integrates better with the object-oriented nature of the language.
- What is a destructor in C++?
Ans) A destructor is a special member function of a class that is executed when an object is destroyed. It has the same name as the class but is preceded by a hyphen (~) and has no return type.
The destructor’s primary purpose is to release resources that the object may have acquired during its lifetime, such as closing files or freeing memory. This helps in preventing memory leaks and other resource-related issues.
- What is a friend function in C++?
Ans) A friend function is a function that is not a member of a class but is allowed to access the class’s private and protected members. It is declared using the keyword “friend” within the class definition. Friend functions are useful when you need to allow certain functions to access private data without providing public methods to expose that data.
- What are the differences between “struct” and “class” in C++?
Ans) The primary difference between “struct” and “class” in C++ is their default access levels. In a “struct” members are public by default, meaning they can be accessed from outside the struct.
In a “class”, members are private by default, meaning they cannot be accessed directly from outside the class. Both can have member functions, constructors, and can use inheritance.
- What is encapsulation in C++?
Ans) Encapsulation is the concept where only relevant part is shown to the user and all the other parts remain hidden from the users access. It restricts direct access to some of the object’s components, which can help protect the integrity of the data by preventing unintended interference and misuse. Encapsulation is achieved using access specifiers like private, protected, and public.
- Explain exception handling in C++.
Ans) Exception handling in C++ is a mechanism to handle errors and unusual conditions in a program. It uses three keywords: ‘try’, ‘catch’, and ‘throw’. You place the code that might cause an error inside a ‘try’ block. If an error occurs, an exception is thrown using ‘throw’ keyword, and the program control is transferred to the ‘catch’ block, where you can handle the error. This helps in keeping the program running smoothly even when unexpected issues occur.
- What is the Standard Template Library (STL) in C++?
Ans) The Standard Template Library (STL) is a collection of pre-written classes and functions for common data structures like vectors, lists, and stacks and algorithms like searching and sorting. It provides efficient and tested implementations, saving your time and effort of writing. Using STL can make your code more strong and easy to maintain.
- What is the use of the “const” keyword in C++?
Ans) The ‘const’ keyword is used to declare constants, meaning their value cannot be changed after they are initialized. It can also be used to make member functions that do not modify the object and to create pointers that cannot change the value they point to. This helps in ensuring that certain values remain constant which improves code safety.
- What are smart pointers in C++?
Ans) Smart pointers are objects that manage the lifetime of dynamically allocated memory. They automatically release memory when it’s no longer needed, preventing memory leaks.
Difference Between C and C++
Below are some common differences between C and C++, which will help you to learn more about both languages and will definitely help you with C Cpp Interview Questions.
C Programming Language | C++ Programming Language |
Procedural Programming Language. | Supports both Object oriented programming and Procedural language. |
There is no data Encapsulation present. | Data encapsulation can be done using classes, Data can be private, public, or protected. |
C Language only supports functions. | It supports functions and methods within classes. |
C language uses malloc and Free for dynamic memory. | C++ uses new and delete for dynamic memory storage. |
Limited or no code reusability. | High code reusability as it supports inheritance |
Limited standard library functions are present. | An extensive standard template library is present for Data structures and algorithms. |
Does not support polymorphism | C++ supports polymorphism through function overloading and virtual functions. |
It does not support virtual and friend functions. | C++ supports both virtual functions and friend functions. |
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C Cpp Interview Questions FAQs
What is the main difference between C and C++?
The main difference is that C is a procedural programming language, while C++ supports both procedural and object-oriented programming. C++ is considered as a superset of C, containing all the features of C and also additional features like- classes, objects, polymorphism, inheritance etc. making it easier to manage and reuse code.
What are some common uses of C and C++?
C and C++ are commonly used for system programming, game development, real-time simulations, embedded systems, and applications requiring high performance, such as databases and operating systems.
How is dynamic memory allocation different in C and C++?
In C, dynamic memory is allocated using “malloc” and freed with “free” function. While In C++, “new” is used to allocate memory and call constructors, and “delete” is used to free memory and call destructors.