C++ is a versatile and powerful programming language that evolved from the C programming language, adding object-oriented programming features while maintaining its low-level capabilities. Developed by Bjarne Stroustrup in the late 1970s, C++ has become a widely used language in various domains such as system programming, game development, and application software.
One of the key features of C++ is its support for object-oriented programming, which allows developers to organize code into classes and objects, promoting code reuse and modularity. Additionally, C++ supports features like templates, which enable generic programming, and allows for both procedural and object-oriented programming paradigms. Its wide range of libraries and extensive community support make it a popular choice for developers seeking a language that combines efficiency with flexibility across a diverse set of applications.
C++ Interview Questions For Freshers
1. What is C++?
C++ is a general-purpose programming language that is an extension of the C programming language. It supports both procedural and object-oriented programming paradigms.
#include <iostream>
int main() {
std::cout << "Hello, World!" << std::endl;
return 0;
}2. What is the difference between C and C++?
| Feature | C | C++ |
|---|---|---|
| Programming Paradigm | Procedural | Multi-paradigm (Procedural and Object-Oriented) |
| Memory Management | Manual (malloc, free) | Automatic (new, delete) and Smart Pointers |
| Syntax and Features | Simpler syntax | Extended syntax with classes, objects, etc. |
| File Handling | Standard I/O functions | File streams with <fstream> library |
| Error Handling | Return values, global variables | Exception handling for structured errors |
| Function Overloading | Not supported | Supported |
| Namespace | Not applicable | Supports namespaces for better code organization |
| Standard Template Library | Limited or no template support | Comprehensive Standard Template Library (STL) |
| Operator Overloading | Limited or no support | Supports operator overloading |
| Constructors/Destructors | Not applicable | Used for automatic resource management in classes |
| Inheritance | Not applicable | Supports inheritance for code reuse |
3. What is Object-Oriented Programming (OOP)?
OOP is a programming paradigm that uses objects (instances of classes) to organize and structure code. It emphasizes concepts such as encapsulation, inheritance, and polymorphism.
4. Explain the concept of a class?
A class is a blueprint for creating objects. It defines a data structure and the methods that can operate on that data.
5. What is an object?
An object is an instance of a class. It represents a real-world entity and encapsulates data and behavior related to that entity.
6. Explain the difference between stack and heap memory?
Stack memory is used for local variables and function call management, while heap memory is dynamically allocated during runtime.
7. What is a constructor?
A constructor is a special member function in a class used for initializing its objects. It has the same name as the class.
8. What is a destructor?
A destructor is a special member function in a class used for cleaning up resources when an object is destroyed.
9. What is the difference between new and malloc()?
new is an operator in C++ for dynamic memory allocation, while malloc() is a function in C. new also calls the constructor for the allocated memory.
10. Explain the concept of function overloading?
Function overloading is the ability to define multiple functions with the same name but different parameters in the same scope.
11. What is the difference between pass by value and pass by reference?
Pass by value sends a copy of the variable to the function, while pass by reference sends the actual variable.
12. What is a pointer?
A pointer is a variable that stores the memory address of another variable.
13. What is a virtual function?
A virtual function is a function in a base class that is declared using the virtual keyword and can be overridden by a derived class.
14. Explain the concept of inheritance?
Inheritance is a mechanism in OOP that allows a class to inherit properties and behaviors from another class.
15. What is polymorphism?
Polymorphism allows objects of different types to be treated as objects of a common base type.
16. What is an abstract class?
An abstract class is a class that cannot be instantiated and may contain abstract methods. It is meant to be subclassed.
17. What is the difference between a class and an object?
A class is a blueprint, and an object is an instance of that blueprint.
18. Explain the concept of operator overloading?
Operator overloading allows you to define how operators work for user-defined types.
19. What is a template in C++?
Templates in C++ allow the creation of generic functions and classes that work with any data type.
20. What is the Standard Template Library (STL)?
STL is a collection of template classes and functions in C++ that provide common data structures and algorithms.
21. What is the keyword ‘this’ used for?
‘this’ is a pointer that points to the object for which the member function is called. It is used to distinguish between class members and local variables.
22. Explain the concept of const keyword?
The ‘const’ keyword is used to declare constant variables, functions, or pointers. It ensures that the value cannot be changed.
23. What is the difference between a shallow copy and a deep copy?
A shallow copy creates a new object but does not duplicate the dynamically allocated memory. A deep copy creates a completely new object with its own copy of the dynamically allocated memory.
24. What is RAII (Resource Acquisition Is Initialization)?
RAII is a programming paradigm where resource management is tied to object lifetime. Resources are acquired in the constructor and released in the destructor.
25. How does exception handling work in C++?
C++ uses try, throw, and catch blocks for exception handling. Code that may throw an exception is placed in a ‘try’ block, and exceptions are caught and handled in ‘catch’ blocks.
26. What is a friend function?
A friend function is a function that is not a member of a class but is allowed to access its private and protected members.
27. Explain the use of ‘typeid’ operator?
‘typeid’ is used to get type information at runtime. It returns a reference to a ‘type_info’ object.
28. What is a smart pointer?
Smart pointers are objects that manage the memory of a dynamically allocated object. They automatically release the memory when the object is no longer needed.
29. What is the purpose of the ‘mutable’ keyword in C++?
‘mutable’ is used to specify that a particular data member of a class can be modified even in a const-qualified member function.
30. How is multiple inheritance handled in C++?
C++ supports multiple inheritance, allowing a class to inherit from more than one base class. Diamond problem, a potential issue in multiple inheritance, can be resolved using virtual inheritance.
C++ Interview Questions For 3 Years Experienced
1. What is the difference between malloc and new in C++?
malloc is a C function for dynamic memory allocation, while new is a C++ operator. new invokes the constructor and returns a pointer to the allocated memory.
2. What is the difference between delete and delete[] in C++?
delete is used to deallocate memory allocated with new, while delete[] is used for memory allocated with new[]. Using the wrong form can lead to undefined behavior.
3. What are the benefits of using references in C++?
References provide a convenient way to alias an existing variable, avoid unnecessary copying, and enable more expressive and readable code.
4. Explain the purpose of the virtual keyword in C++?
virtual is used to declare a member function as virtual in a base class. It enables dynamic polymorphism and allows derived classes to provide their own implementation.
5. What is the difference between const and constexpr in C++?
const is used to indicate that a variable’s value cannot be modified, while constexpr indicates that a value or function can be evaluated at compile time.
6. What is a lambda function in C++?
A lambda function is an anonymous function defined using the lambda expression. It allows for the creation of small, inline functions without the need for a formal function declaration.
7. How does an inline function differ from a normal function in C++?
Inline functions are expanded at the point of their call, reducing the function call overhead. They are suggested to the compiler using the inline keyword, but the compiler may choose to ignore it.
8. Explain the difference between override and final in C++?
override is used to indicate that a function in a derived class is intended to override a virtual function in the base class. final is used to prevent further overriding of a virtual function.
9. What is the purpose of the typeid operator in C++?
typeid is used to obtain information about an object’s type at runtime. It is often used in conjunction with polymorphism and dynamic casting.
10. What is the difference between unique_ptr and shared_ptr in C++?
unique_ptr represents sole ownership of an object and is more efficient. shared_ptr allows multiple pointers to share ownership of the same object.
11. How does exception handling work in C++?
Exception handling in C++ involves the use of try, catch, and throw statements. try encloses the code that might throw an exception, and catch handles the exception if one occurs.
12. Explain the concept of a smart pointer in C++?
Smart pointers are objects that act like pointers but also manage the memory they point to. std::unique_ptr and std::shared_ptr are examples provided by the C++ Standard Library.
13. What is the purpose of the volatile keyword in C++?
volatile is used to indicate that a variable’s value may be changed by external sources outside the program’s control, preventing the compiler from making optimizations based on the assumption of unchanged values.
14. How does function overloading work in C++?
Function overloading allows multiple functions with the same name but different parameter lists. The compiler determines the correct function to call based on the number and types of arguments provided.
15. What is the role of the const member function in C++?
A const member function is a member function that promises not to modify the object it is called on. It is indicated by the const keyword at the end of the function declaration.
16. Explain the concept of a copy constructor in C++?
A copy constructor is a special constructor that creates an object by copying the values of another object. It is invoked when an object is passed by value, returned by value, or explicitly called.
17. What is the purpose of the namespace keyword in C++?
namespace is used to organize code into separate, logical units, preventing naming conflicts. It helps improve code modularity and readability.
18. How is polymorphism achieved in C++?
Polymorphism in C++ is achieved through function overloading and virtual functions. Dynamic polymorphism is facilitated by using pointers or references to base class types.
19. What are the differences between deep copy and shallow copy?
Deep copy involves creating a new object and copying the values of the members, including any dynamically allocated memory. Shallow copy only copies the memory addresses of the members, not the actual data.
20. How are static and dynamic linking different in C++?
Static linking involves linking the entire code at compile time, while dynamic linking links the code at runtime. Dynamic linking allows for more flexibility and smaller executable sizes.
21. Explain the role of the explicit keyword in C++?
The explicit keyword is used to prevent implicit type conversions in constructors or conversion operators. It ensures that a type conversion is only performed when explicitly requested.
22. What is the significance of the mutable keyword in C++?
The mutable keyword is used to indicate that a member of a class can be modified even if the object is declared as const. It is often used in scenarios where a logical concept of constness is maintained.
23. How does a virtual destructor work in C++?
A virtual destructor ensures that the destructor of the most derived class is called when deleting a pointer to a base class. This is crucial for proper cleanup in polymorphic class hierarchies.
24. What is the role of the std::move function in C++?
std::move is used to convert an lvalue into an rvalue, allowing for efficient move semantics. It is often used in conjunction with move constructors and move assignment operators.
25. How does the decltype keyword work in C++?
decltype is used to deduce the type of an expression at compile time. It is often used in template metaprogramming and situations where the type needs to be automatically determined.
26. Explain the purpose of the auto keyword in C++11 and later versions?
auto is used for automatic type inference, allowing the compiler to deduce the type of a variable based on its initializer. It simplifies code and enhances readability.
27. What are the advantages of using the Standard Template Library (STL) in C++?
STL provides a collection of reusable algorithms and data structures, promoting code reuse, readability, and maintainability. It includes containers, algorithms, iterators, and other components.
28. How does the friend keyword work in C++?
The friend keyword is used to grant non-member functions or other classes access to private or protected members of a class. It is often used to establish relationships between classes without compromising encapsulation.
C++ Interview Questions For 10 years Experience
1. What is the Rule of Three in C++?
The Rule of Three states that if a class defines one of the following three special member functions (destructor, copy constructor, or copy assignment operator), it should define all three.
2. Explain the use of the explicit keyword with constructors?
The explicit keyword in a constructor prevents implicit type conversions and is particularly useful to avoid unexpected type conversions in C++.
3. What is the difference between nullptr and NULL in C++11 and later versions?
In C++11 and later, nullptr is a keyword that represents a null pointer of any type, providing type safety. NULL is an old-style macro typically defined as 0 or (void*)0, which may lead to ambiguities.
4. What are the advantages and disadvantages of using multiple inheritance in C++?
Advantages include code reuse and the ability to model complex relationships. Disadvantages involve the potential for ambiguity and the “diamond problem” where ambiguity arises due to shared base classes.
5. Explain the difference between const and constexpr in C++11 and later versions?
const is used to indicate that a variable’s value cannot be modified, while constexpr indicates that a value or function can be evaluated at compile time. constexpr is a stronger guarantee of immutability.
6. What is a lambda function in C++11 and later versions? Provide an example.
A lambda function in C++11 and later versions is an anonymous function that can be defined inline within the code. It provides a concise way to create small, reusable functions without the need for a formal function declaration. Lambda functions are particularly useful in scenarios where a simple function is needed for a short duration and defining a separate function seems verbose. Here’s a basic example of a lambda function:
#include <iostream>
int main() {
// Lambda function that takes two integers and returns their sum
auto add = [](int a, int b) {
return a + b;
};
// Using the lambda function
int result = add(3, 5);
// Displaying the result
std::cout << "Result: " << result << std::endl;
return 0;
}7. How does move semantics improve performance in C++?
Move semantics allow the efficient transfer of resources from one object to another, reducing the need for deep copying and improving performance. It is implemented through move constructors and move assignment operators.
8. What is SFINAE (Substitution Failure Is Not An Error) in C++ template metaprogramming?
SFINAE is a C++ mechanism that allows the substitution of invalid template parameters to fail silently, instead of causing a compilation error. It is often used in template specialization and overloading.
9. Explain the purpose of the noexcept specifier in C++?
The noexcept specifier indicates that a function does not throw exceptions. It is used for both optimization and to enable better code analysis. For example, void myFunction() noexcept;
10. How does the std::unique_lock differ from std::lock_guard in C++ threading?
std::unique_lock provides more flexibility than std::lock_guard. It can be locked and unlocked multiple times, and it supports deferred locking and timed locking, offering more control over locking strategies.
11. What is the purpose of the std::initializer_list in C++?
std::initializer_list is a C++ feature that allows the easy initialization of objects with a brace-enclosed list of values. It is commonly used in constructors and functions to accept a variable number of arguments.
12. How does CRTP (Curiously Recurring Template Pattern) work in C++?
CRTP is a design pattern where a class template inherits from a class using itself as a template argument. It enables static polymorphism without the overhead of virtual functions.
13. Explain the purpose of the std::tuple in C++?
std::tuple is a C++ template class that allows the creation of heterogenous collections of elements. It is often used in scenarios where a fixed number of elements with different types need to be grouped together.
14. What is the purpose of the std::unique algorithm in C++?
std::unique is an algorithm in the C++ Standard Template Library (STL) that eliminates consecutive duplicate elements from a range. It rearranges the elements and returns an iterator pointing to the end of the unique range.
15. Explain the usage of the std::forward function in C++?
std::forward is used in perfect forwarding, allowing the preservation of value categories (lvalue or rvalue) when forwarding arguments in templates. It is commonly used in implementing generic functions, especially in combination with templates and variadic templates.
16. What are variadic templates in C++?
Variadic templates are a C++ feature introduced in C++11 that allows the definition of functions and classes that accept a variable number of template arguments. They are particularly useful for creating generic functions and containers.
17. How does the std::async function work in C++ for asynchronous programming?
std::async is a C++ function template that creates a new asynchronous task and returns a std::future representing the result of the task. It is part of the C++ Standard Library’s support for asynchronous programming.
18. What is the role of the std::enable_if template in C++?
std::enable_if is a C++ template meta-programming feature used to conditionally enable or disable a function or class template based on a compile-time condition. It is often used in conjunction with SFINAE.
19. Explain the purpose of the std::move_if_noexcept function in C++?
std::move_if_noexcept is a C++ utility function that conditionally performs a move operation if the move constructor or move assignment operator is marked as noexcept. It is often used to optimize move semantics.
20. What are user-defined literals in C++11 and later versions?
User-defined literals allow users to define their own literal suffixes for literals of user-defined types. It enhances the expressiveness of code by allowing custom syntax for user-defined types.
21. How does the std::optional class in C++17 improve handling of optional values?
std::optional is a C++ class template introduced in C++17 that represents an optional value, either containing a value or nothing. It provides a safer and more expressive alternative to using null pointers or sentinel values.
22. What are the benefits of using the std::filesystem library introduced in C++17?
The std::filesystem library provides a comprehensive set of facilities for performing operations on file systems. It simplifies file and directory manipulations, making file I/O operations more convenient and platform-independent.
23. Explain the purpose of the std::variant class template in C++17?
std::variant is a C++ class template introduced in C++17 that represents a type-safe union of types. It provides a safer alternative to traditional unions, allowing the storage of values of different types without the risk of undefined behavior.
24. How does the C++20 concept feature improve template programming?
Concepts in C++20 provide a way to specify constraints on template parameters, allowing for clearer error messages, better code readability, and improved template metaprogramming. They replace some of the complex SFINAE-based code.
25. What is the purpose of the spaceship operator (<=>) introduced in C++20?
The spaceship operator is a three-way comparison operator introduced in C++20. It simplifies the implementation of comparison operators by providing a concise and standardized way to express comparisons.
26. How does the std::coroutine feature in C++20 facilitate asynchronous programming?
The std::coroutine feature introduces coroutines, which are a way to write asynchronous code more naturally. Coroutines allow suspending and resuming the execution of a function, facilitating asynchronous operations without callback-based code.
27. Explain the purpose of the ranges library introduced in C++20?
The ranges library in C++20 provides a set of powerful and composable components for working with ranges of values. It introduces a more expressive and functional approach to working with sequences, simplifying code and improving readability.
28. What are the improvements introduced in C++23?
As of my knowledge cutoff in January 2022, specific features of C++23 may not be available. However, C++ continues to evolve, and improvements are typically aimed at enhancing language features, standard library components, and providing better tools for developers.
29. How does C++ support reflection, and what are the proposals related to reflection?
As of my last knowledge update in January 2022, C++ does not have native support for reflection. Various proposals, such as P0194R2, have been discussed to introduce reflection features in future C++ standards. These proposals aim to provide mechanisms for introspecting and manipulating types at runtime.
30. What are some best practices for exception handling in C++?
Best practices for exception handling in C++ include using exceptions for exceptional, error-like conditions, not using exceptions for normal control flow, catching exceptions by reference, and using the RAII principle for resource management. Additionally, avoid catching all exceptions indiscriminately and prefer returning error codes or using alternative error-handling mechanisms when appropriate.
Frequently Asked Questions
RTTI stands for Run-Time Type Information in C++. It is a feature that allows a program to obtain information about the type of an object at runtime. RTTI is particularly useful in situations where polymorphism is employed, and there’s a need to determine the actual type of an object pointed to by a base class pointer or referenced by a base class reference.
In C++, a token is the smallest unit in the source code that has a specific meaning to the compiler. The C++ language supports several types of tokens, which can be categorized into the following main groups: Keywords, Identifiers, Literals, Operators, Punctuators, Comments, Preprocessor Directives, Special Symbols.
In C++, a pure virtual function is a virtual function that is declared in a base class but has no implementation. It serves as a blueprint for derived classes, indicating that any derived class must provide its own implementation for the pure virtual function. A class containing at least one pure virtual function is known as an abstract class, and objects of abstract classes cannot be instantiated.
Containership, in the context of programming and software development, typically refers to the concept of one class or data structure being contained within another. It involves organizing and structuring classes or objects in a way that allows one to encapsulate or hold instances of another.