In this article, we present a curated selection of difficult C++ Programming MCQs that will put your knowledge to the test. These questions delve into various advanced topics and intricacies of the C++ Programming language, covering concepts such as memory management, templates, operator overloading, and more. So, gear up for a stimulating intellectual exercise as we dive into this collection of C++ MCQs.

Aspiring programmers and seasoned developers alike understand the importance of continuously sharpening their coding skills. One language that has stood the test of time and remains a cornerstone of software development is C++ Programming Language. Whether you are a student preparing for exams or a professional aiming to enhance your expertise, it’s essential to test your understanding through challenging multiple-choice questions (MCQs).

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This MCQ Covers questions in all of the fields Object-oriented programming, Variables, Functions, Control structures, Pointers, Arrays, Classes, Inheritance, Polymorphism, Templates, Exception handling, Memory management, File handling, Constructors, Destructors, Encapsulation, Abstraction, Operator overloading, Virtual functions, Dynamic memory allocation, Standard Template Library (STL), Recursion, Namespaces, Const keyword, Typecasting.

C++ Programming Multiple-Choice Questions(Difficult Level)

Challenging C++ Multiple Choice Questions (Difficult Level)

What is the output of the following code snippet?

#include <iostream>

int main() {
    int x = 10;
    if (x > 5) {
        int x = 5;
        std::cout << x << std::endl;
    }
    std::cout << x << std::endl;
    return 0;
}

a) 5 10
b) 6 10
c) 5 9
d) 5 5

Answer: a) 5 10

What is the purpose of the explicit keyword in C++?

a) It is used to convert one type to another implicitly.
b) It is used to indicate that a function is a constructor.
c) It is used to prevent automatic type conversions.
d) It is used to define a pure virtual function.

Option (c) is correct. The explicit keyword is used to prevent automatic type conversions. It can be used with constructors to prevent implicit conversions from the constructor’s argument type to the class type.

Which of the following statements about function templates in C++ is true?

a) Function templates can only be defined in the global scope.
b) Function templates cannot have default arguments.
c) Function templates cannot be overloaded.
d) Function templates can be specialized for specific types.

Option (d) is correct. Function templates in C++ can be specialized for specific types, allowing you to provide custom implementations for specific type arguments.

What is the difference between std::vector and std::array in C++?

a) std::vector is a dynamic array, while std::array is a fixed-size array.
b) std::vector is a fixed-size array, while std::array is a dynamic array.
c) std::vector provides constant-time random access, while std::array does not.
d) std::array provides dynamic resizing, while std::vector does not.

Option (a) is correct. std::vector is a dynamic array that can resize itself, while std::array is a fixed-size array with a predetermined size that cannot be changed after its creation.

What is the output of the following code snippet?

#include <iostream>

class Base {
public:
    virtual void print() {
        std::cout << "Base" << std::endl;
    }
};

class Derived : public Base {
public:
    void print() override {
        std::cout << "Derived" << std::endl;
    }
};

int main() {
    Base* ptr = new Derived();
    ptr->print();
    delete ptr;
    return 0;
}

a) Derived.
b) Base.
c) new Derived.
d) None of these.

Option (a) is correct. Derived.

What is the purpose of the typeid operator in C++?

a) It returns the type of a variable.
b) It checks if a type is polymorphic.
c) It returns the size of a type in bytes.
d) It converts a type to another type.

Option (a) is correct. The typeid operator in C++ returns the type of a variable or an expression at runtime.

Which of the following is true regarding the const keyword in C++?

a) A const object cannot be modified.
b) A const member function cannot modify the object’s state.
c) A const reference can only bind to a const object.
d) All of the above.

Option (d) is correct. All of the statements are true regarding the const keyword in C++.

What is the output of the following code snippet?

#include <iostream>

void increment(int& x) {
    x++;
}

int main() {
    const int x = 5;
    increment(const_cast<int&>(x));
    std::cout << x << std::endl;
    return 0;
}

a) 6
b) 5
c) Garbage Value
d) 0

Option (b) is correct. 5

What is the purpose of the volatile keyword in C++?

a) It indicates that a variable is not initialized.
b) It ensures that a variable is always initialized to 0.
c) It prevents the compiler from optimizing accesses to a variable.
d) It prevents a variable from being modified.

Option (c) is correct. The volatile keyword in C++ prevents the compiler from optimizing accesses to a variable, indicating that the variable may change unexpectedly due to external factors.

Which of the following is an example of a valid C++ lambda expression?

a) []() { }
b) []() { return 42; }
c) [](int x) { return x * 2; }
d) All of the above.

Option (d) is correct. All of the given lambda expressions are valid in C++. Lambda expressions are anonymous functions that can capture variables from their surrounding scope and can have various forms.

What is the output of the following code snippet?

#include <iostream>

int main() {
    int arr[5] = {1, 2, 3, 4, 5};
    int* ptr = arr;
    std::cout << *ptr++ << std::endl;
    std::cout << *ptr++ << std::endl;
    return 0;
}

a) 1 1
b) 2 3
c) 0 1
d) 1 2

Answer: d) 1 2. Explanation: The code defines an array arr and a pointer ptr that initially points to the first element of the array. The *ptr++ expression increments the pointer after accessing the value it points to.

What is the purpose of the std::move function in C++?

a) It converts an lvalue to an rvalue reference.
b) It converts an rvalue to an lvalue reference.
c) It moves the content of one object to another.
d) It creates a new object from an existing one.

Option (a) is correct. The std::move function in C++ converts an lvalue to an rvalue reference, allowing the object’s resources to be moved efficiently rather than copied.

Which of the following is true regarding virtual destructors in C++?

a) A class with a virtual destructor cannot be inherited.
b) A virtual destructor ensures that derived class destructors are called.
c) A virtual destructor prevents the deletion of objects.
d) A virtual destructor is used to free memory allocated by new.

Option (b) is correct. A virtual destructor in C++ ensures that derived class destructors are called when deleting objects through a base class pointer. It is important to make the base class destructor virtual to avoid undefined behavior when deleting derived class objects through a base class pointer.

What is the output of the following code snippet?

#include <iostream>

int main() {
    int x = 10;
    int y = 20;
    int* ptr = &x;
    *ptr++ = y;
    std::cout << x << " " << y << std::endl;
    return 0;
}

a) 10 10.
b) 10 20.
c) 20 20
d) None of these.

Option (b) is correct. 10 20.

What is the output of the following code snippet?

#include <iostream>

int main() {
    int arr[] = {1, 2, 3, 4, 5};
    int* ptr = arr;
    std::cout << *(ptr + 2) << std::endl;
    std::cout << *ptr + 2 << std::endl;
    return 0;
}

a) 2 2
b) 3 3
c) 3 5
d) None of these.

Option (b) is correct. 3 3.

What is the purpose of the std::nothrow parameter in C++?

a) It prevents exceptions from being thrown.
b) It enables exceptions to be thrown.
c) It allows dynamic memory allocation without throwing exceptions.
d) It specifies the type of exception to be thrown.

Option (c) is correct. The std::nothrow parameter, when used with dynamic memory allocation functions like new or new[], allows the functions to return a null pointer instead of throwing an exception when memory allocation fails.

What is the output of the following code snippet?

#include <iostream>

int main() {
    int x = 10;
    int* ptr = &x;
    int& ref = *ptr;
    std::cout << x << " " << ref << std::endl;
    *ptr = 20;
    std::cout << x << " " << ref << std::endl;
    return 0;
}

a) 10 20 10 20
b) 10 10 20 20
c) 20 20 10 10
d) None of these

Option (b) is correct. 10 10 20 20

Which of the following is an example of runtime polymorphism in C++?

a) Function overloading
b) Operator overloading
c) Virtual functions
d) Templates

Option (c) is correct. Virtual functions in C++ allow for runtime polymorphism, where the appropriate function to call is determined based on the actual type of the object rather than the static type of the pointer or reference.

What is the output of the following code snippet?

#include <iostream>

class Base {
public:
    Base() {
        std::cout << "Base constructor" << std::endl;
    }
    virtual ~Base() {
        std::cout << "Base destructor" << std::endl;
    }
};

class Derived : public Base {
public:
    Derived() {
        std::cout << "Derived constructor" << std::endl;
    }
    ~Derived() {
        std::cout << "Derived destructor" << std::endl;
    }
};

int main() {
    Base* ptr = new Derived();
    delete ptr;
    return 0;
}

a) Derived constructor
Base constructor
Derived destructor
Base destructor
b) Derived constructor
Derived destructor
Base constructor
Base destructor
c) Base constructor
Base destructor
Derived constructor
Derived destructor
d) None of these

Option (a) is correct.

Which of the following is true regarding the delete operator in C++?

a) It frees the memory allocated by new.
b) It can be used to delete individual elements of an array.
c) It calls the destructor of the object being deleted.
d) All of the above.

Option (d) is correct. The delete operator in C++ is used to free the memory allocated by new, and it calls the destructor of the object being deleted. It can also be used to delete individual elements of an array allocated with new[].

What is the purpose of the std::unique_ptr class in C++?

a) It provides a smart pointer that automatically deletes objects.
b) It allows multiple pointers to refer to the same object.
c) It manages memory allocation for dynamic arrays.
d) It provides reference counting for shared ownership.

Option (a) is correct. The std::unique_ptr class in C++ provides a smart pointer that automatically deletes objects when they are no longer needed. It ensures that only one std::unique_ptr can own the object, preventing multiple pointers from referring to the same object.

What is the purpose of the explicit specifier for a constructor in C++?

a) It allows implicit conversion from the constructor’s argument type to the class type.
b) It prevents automatic type conversions for the constructor.
c) It makes the constructor callable with no arguments.
d) It enables the constructor to be virtual.

Option (b) is correct. The explicit specifier for a constructor in C++ prevents automatic type conversions for the constructor’s arguments, which helps avoid unintended implicit conversions.

What is the output of the following code snippet?

#include <iostream>

int main() {
    int x = 5;
    int y = x > 2 ? x++ : ++x;
    std::cout << x << " " << y << std::endl;
    return 0;
}

a) 6 5
b) 5 5
c) 6 6
d) None of these.

Option (a) is correct. 6 5.

Which of the following is true regarding the const member functions in C++?

a) They can modify the object’s state.
b) They cannot modify the object’s state.
c) They can only be called on const objects.
d) They cannot be called on const objects.

Option (b) is correct. const member functions in C++ are member functions that promise not to modify the object’s state. They are allowed to read the object’s state but cannot modify it. They can be called on both const and non-const objects.

What is the purpose of the std::initializer_list in C++?

a) It allows for the initialization of arrays with a list of values.
b) It enables the creation of user-defined literals.
c) It provides a way to iterate over the elements of a container.
d) It allows for the creation of compile-time constant values.

Option (a) is correct. The std::initializer_list in C++ allows for the initialization of arrays and other containers with a list of values. It provides a convenient syntax for initializing containers with multiple elements.

What is the output of the following code snippet?

#include <iostream>

int main() {
    int x = 5;
    int y = ++x * 2;
    std::cout << x << " " << y << std::endl;
    return 0;
}

a) 6 5
b) 5 5
c) 6 6
d) None of these.

Option (d) is correct. Answer is 6 12.

Which of the following is true regarding the mutable specifier in C++?

a) It allows a variable to be modified inside a const member function.
b) It makes a member function const.
c) It prevents a member function from modifying the object’s state.
d) It allows a variable to be shared among multiple objects

Option (a) is correct. The mutable specifier in C++ allows a variable to be modified inside a const member function. It overrides the constness of the member function and allows changes to mutable data members.

Which of the following is true regarding the std::vector class in C++?

a) It is a fixed-size container.
b) It provides constant-time random access to elements.
c) It does not allow for the insertion or removal of elements.
d) It can only store elements of the same type.

Option (b) is correct. The std::vector class in C++ provides constant-time random access to elements. It is a dynamic array-like container that allows for the insertion, removal, and resizing of elements. It can store elements of different types since it is a template class.

What is the output of the following code snippet?

#include <iostream>

int main() {
    int x = 5;
    int y = 2;
    int z = x / y;
    std::cout << z << std::endl;
    return 0;
}

a) 2
b) 1
c) 5
d) 2.5

Option (a) is correct. 2

Which of the following is true regarding the const keyword in C++?

a) It prevents a variable from being modified.
b) It makes a variable constant and unchangeable.
c) It can be used to create constant pointers.
d) All of the above.

Option (d) is correct. The const keyword in C++ is used to declare variables that cannot be modified, create constant pointers, and make variables constant and unchangeable.

Which of the following is true regarding the static keyword in C++?

a) It specifies that a variable belongs to a specific instance of a class.
b) It allows a variable to be accessed from any file in a program.
c) It makes a variable visible only within the current source file.
d) It causes a variable to retain its value between function calls.

Option (d) is correct. The static keyword in C++ causes a variable to retain its value between function calls. It is also used to specify static class members and restrict the scope of variables and functions to the current source file.

Mastering C++ requires dedication, practice, and a deep understanding of its complexities. By engaging with challenging MCQs, you not only assess your current knowledge but also identify areas for improvement. The questions presented in this article offer a glimpse into the intricate world of C++ programming, encouraging you to think critically and explore different aspects of the language.

Remember, don’t be disheartened if you stumble upon some questions that prove challenging. Learning from your mistakes and seeking further understanding will ultimately lead to growth and mastery. Keep pushing your boundaries, and honing your C++ skills, and you’ll soon find yourself capable of tackling even the most demanding programming tasks with confidence.

So, let’s begin this exciting journey of testing your C++ knowledge with these difficult MCQs. Good luck!

Challenging C++ Multiple Choice Questions (Difficult Level)

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