C++ - Interview MCQ & Answers

Interview MCQ & Answers in C++

1. What is the size of `int` in C++?

Answer: The size of `int` is typically 4 bytes on most modern systems, but it can vary based on the architecture.

2. Which of the following is a correct comment syntax in C++?

Answer:
- Single line comment: // This is a comment
- Multi-line comment: /* This is a comment */

3. What is the difference between `++i` and `i++`?

Answer:
- `++i` is a pre-increment operator, which increments the value of `i` before using it.
- `i++` is a post-increment operator, which increments the value of `i` after using it.

4. What is a constructor in C++?

Answer:
A constructor is a special member function in a class that is automatically called when an object of the class is created. It is used to initialize objects.

5. What is the difference between `new` and `malloc()` in C++?

Answer:
- `new` is an operator in C++ that allocates memory and calls the constructor for an object.
- `malloc()` is a C library function that allocates memory but does not call the constructor.

6. What is a virtual function in C++?

Answer:
A virtual function is a function in a base class that is overridden in a derived class. It is used to achieve runtime polymorphism.

7. What is the use of `virtual` keyword in C++?

Answer:
The `virtual` keyword is used to indicate that a function can be overridden in a derived class. It helps achieve runtime polymorphism.

8. What does `namespace` mean in C++?

Answer:
A `namespace` is a container for identifiers such as variables, functions, and classes. It helps avoid name conflicts in large programs.

9. What is the output of the following code?

        
        #include 
        using namespace std;
        
        int main() {
            int x = 10;
            cout << ++x;
            return 0;
        }
        
    

Answer:
Output: 11

10. What are the different types of inheritance in C++?

Answer:
The different types of inheritance in C++ are:
- Single Inheritance
- Multiple Inheritance
- Multilevel Inheritance
- Hierarchical Inheritance
- Hybrid Inheritance

11. What is the purpose of the `this` pointer in C++?

Answer:
The `this` pointer is an implicit pointer in C++ that points to the current object in a non-static member function.

12. What is the difference between a reference and a pointer in C++?

Answer:
- A reference is an alias for another variable and cannot be null.
- A pointer is a variable that stores the memory address of another variable and can be null.

13. What is dynamic memory allocation in C++?

Answer:
Dynamic memory allocation refers to allocating memory at runtime using operators like `new` and `delete` instead of at compile-time.

14. What is the difference between `struct` and `class` in C++?

Answer:
The main difference is that by default, members of a `struct` are public, while members of a `class` are private.

15. What is the use of `friend` function in C++?

Answer:
A `friend` function is a function that is not a member of a class but can access its private and protected members.

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C++

Beginner 5 Hours

Interview MCQ & Answers in C++

1. What is the size of `int` in C++?

Answer: The size of `int` is typically 4 bytes on most modern systems, but it can vary based on the architecture.

2. Which of the following is a correct comment syntax in C++?

Answer:
- Single line comment: // This is a comment
- Multi-line comment: /* This is a comment */

3. What is the difference between `++i` and `i++`?

Answer:
- `++i` is a pre-increment operator, which increments the value of `i` before using it.
- `i++` is a post-increment operator, which increments the value of `i` after using it.

4. What is a constructor in C++?

Answer:
A constructor is a special member function in a class that is automatically called when an object of the class is created. It is used to initialize objects.

5. What is the difference between `new` and `malloc()` in C++?

Answer:
- `new` is an operator in C++ that allocates memory and calls the constructor for an object.
- `malloc()` is a C library function that allocates memory but does not call the constructor.

6. What is a virtual function in C++?

Answer:
A virtual function is a function in a base class that is overridden in a derived class. It is used to achieve runtime polymorphism.

7. What is the use of `virtual` keyword in C++?

Answer:
The `virtual` keyword is used to indicate that a function can be overridden in a derived class. It helps achieve runtime polymorphism.

8. What does `namespace` mean in C++?

Answer:
A `namespace` is a container for identifiers such as variables, functions, and classes. It helps avoid name conflicts in large programs.

9. What is the output of the following code?

        
#include using namespace std; int main() { int x = 10; cout << ++x; return 0; }

Answer:
Output: 11

10. What are the different types of inheritance in C++?

Answer:
The different types of inheritance in C++ are:
- Single Inheritance
- Multiple Inheritance
- Multilevel Inheritance
- Hierarchical Inheritance
- Hybrid Inheritance

11. What is the purpose of the `this` pointer in C++?

Answer:
The `this` pointer is an implicit pointer in C++ that points to the current object in a non-static member function.

12. What is the difference between a reference and a pointer in C++?

Answer:
- A reference is an alias for another variable and cannot be null.
- A pointer is a variable that stores the memory address of another variable and can be null.

13. What is dynamic memory allocation in C++?

Answer:
Dynamic memory allocation refers to allocating memory at runtime using operators like `new` and `delete` instead of at compile-time.

14. What is the difference between `struct` and `class` in C++?

Answer:
The main difference is that by default, members of a `struct` are public, while members of a `class` are private.

15. What is the use of `friend` function in C++?

Answer:
A `friend` function is a function that is not a member of a class but can access its private and protected members.

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Frequently Asked Questions for C++

A void pointer is a special type of pointer that can point to any data type, making it versatile for generic data handling.

Dynamic memory allocation in C++ refers to allocating memory at runtime using operators like new and delete, providing flexibility in memory management.

Templates in C++ allow functions and classes to operate with generic types, enabling code reusability and type safety.

Iterators are objects that allow traversal through the elements of a container in the STL, providing a uniform way to access elements.

C++ is an object-oriented programming language that extends C by adding features like classes, inheritance, and polymorphism. Unlike C, which is procedural, C++ supports both procedural and object-oriented paradigms.

An array in C++ is declared by specifying the type of its elements followed by the array name and size in square brackets, e.g., int arr[10];.

The new operator allocates memory dynamically on the heap, while the delete operator deallocates memory, preventing memory leaks.

Type casting in C++ is the process of converting a variable from one data type to another, either implicitly or explicitly.

Inheritance is a feature in C++ where a new class (derived class) acquires properties and behaviors (methods) from an existing class (base class).

Operator overloading enables the redefinition of the way operators work for user-defined types, allowing operators to be used with objects of those types.

Function overloading allows multiple functions with the same name but different parameters to coexist in a C++ program, enabling more intuitive function calls.

In C++, a class is declared using the class keyword, followed by the class name and a pair of curly braces containing member variables and functions.

No, a C++ program cannot execute without a main() function, as it is the designated entry point for program execution.

Vectors are dynamic arrays provided by the STL in C++ that can grow or shrink in size during program execution.

A namespace in C++ is a declarative region that provides a scope to the identifiers (names of types, functions, variables) to avoid name conflicts.

The primary difference is that members of a struct are public by default, whereas members of a class are private by default.

The const keyword in C++ is used to define constants, indicating that the value of a variable cannot be changed after initialization.

Exception handling in C++ is a mechanism to handle runtime errors using try, catch, and throw blocks, allowing a program to continue execution after an error.

The STL is a collection of template classes and functions in C++ that provide general-purpose algorithms and data structures like vectors, lists, and maps.

A reference in C++ is an alias for another variable, whereas a pointer holds the memory address of a variable. References cannot be null and must be initialized upon declaration.

Pointers in C++ are variables that store memory addresses of other variables. They allow for dynamic memory allocation and efficient array handling.

Polymorphism allows objects of different classes to be treated as objects of a common base class, enabling a single function or operator to work in different ways.

Constructors are special member functions that initialize objects when they are created. Destructors are called when objects are destroyed, used to release resources.

These access specifiers define the accessibility of class members. Public members are accessible from outside the class, private members are not, and protected members are accessible within the class and by derived classes.

The main() function serves as the entry point for a C++ program. It is where the execution starts and ends.

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