C++ Memory Management Quiz - MCQ Questions and Answers

Welcome to our "C++ Memory Management Quiz," a resource designed to test and enhance your understanding of one of the most crucial aspects of C++ programming: memory management. This quiz comprises a series of multiple-choice questions (MCQs) that delve into the core concepts of dynamic memory allocation, pointers, memory leaks, and more. 

Each question is accompanied by an in-depth explanation, providing a comprehensive learning experience. Whether you're prepping for an interview, an exam, or simply looking to brush up on your C++ memory management skills, this quiz is for you. Let's get started and see how much you really know about managing memory in C++!

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

a) Allocating memory at compile time

b) Automatically managing memory

c) Allocating memory during runtime

d) Increasing the size of the stack

Answer:

c) Allocating memory during runtime

Explanation:

Dynamic memory allocation in C++ refers to the process of allocating memory for variables at runtime using operators like 'new' and 'delete'.

2. Which operator is used to allocate memory dynamically in C++?

a) malloc

b) alloc

c) new

d) create

Answer:

c) new

Explanation:

The 'new' operator is used in C++ for dynamic memory allocation. It allocates memory on the heap for a variable or an array and returns a pointer to the allocated memory.

3. What is the purpose of the 'delete' operator in C++?

a) To delete variables from the stack

b) To free dynamically allocated memory

c) To remove values from an array

d) To terminate the program

Answer:

b) To free dynamically allocated memory

Explanation:

The 'delete' operator in C++ is used to free memory that was previously allocated dynamically using the 'new' operator.

4. How is memory allocated for an array dynamically in C++?

a) int* arr = new int[10];

b) int arr = new int[10];

c) int arr[10] = new int;

d) int* arr = alloc int[10];

Answer:

a) int* arr = new int[10];

Explanation:

Dynamic memory for an array is allocated using the 'new' operator followed by the data type and the size of the array in square brackets.

5. What is a memory leak in C++?

a) When the program uses too much memory

b) When memory is not allocated properly

c) When dynamically allocated memory is not freed

d) When the program tries to access restricted memory

Answer:

c) When dynamically allocated memory is not freed

Explanation:

A memory leak occurs when a program in C++ dynamically allocates memory and fails to free it, leading to a waste of memory resources.

6. Which of the following is not a valid way to allocate memory dynamically for an integer in C++?

a) int* ptr = new int;

b) int* ptr = new int(10);

c) int* ptr = new;

d) int* ptr = new int[1];

Answer:

c) int* ptr = new;

Explanation:

The expression 'int* ptr = new;' is not a valid way to allocate memory dynamically as it lacks the data type after the 'new' keyword.

7. What happens when you use the 'delete' operator on a pointer that is not dynamically allocated?

a) The program will successfully delete the pointer

b) It will cause a runtime error

c) The compiler will produce an error

d) It may lead to undefined behavior

Answer:

d) It may lead to undefined behavior

Explanation:

Using 'delete' on a pointer not allocated with 'new' can lead to undefined behavior, including crashes or memory corruption.

8. How do you allocate and initialize memory for a single integer to 5 in C++?

a) int* ptr = new int(5);

b) int* ptr = new int = 5;

c) int* ptr = new int[5];

d) int* ptr = new int(1, 5);

Answer:

a) int* ptr = new int(5);

Explanation:

The correct way to allocate and initialize a single integer to 5 is 'int* ptr = new int(5);', which uses the 'new' operator with an initializer.

9. What is a dangling pointer in C++?

a) A pointer that has not been initialized

b) A pointer that points to an invalid memory location

c) A pointer that points to a static variable

d) A pointer that points to multiple locations

Answer:

b) A pointer that points to an invalid memory location

Explanation:

A dangling pointer is a pointer that points to a memory location that has been freed or is no longer valid.

10. What does the 'delete[]' operator do in C++?

a) Deletes an array from the stack

b) Frees memory allocated for a single variable

c) Frees memory allocated for an array

d) Deletes a pointer

Answer:

c) Frees memory allocated for an array

Explanation:

The 'delete[]' operator is used to free memory that was allocated for an array using 'new[]'.

11. What is the output of the following C++ code?

   int* ptr = new int;
   *ptr = 10;
   delete ptr;
   cout << *ptr;

a) 0

b) 10

c) Garbage value

d) Runtime error

Answer:

c) Garbage value

Explanation:

After deleting 'ptr', it becomes a dangling pointer, and dereferencing it results in a garbage value, as the memory location it points to is no longer valid.

12. How do you prevent a memory leak in C++?

a) By using the malloc function

b) By not using dynamic memory allocation

c) By freeing dynamically allocated memory using 'delete' or 'delete[]'

d) By using static memory allocation only

Answer:

c) By freeing dynamically allocated memory using 'delete' or 'delete[]'

Explanation:

To prevent memory leaks in C++, it is essential to free dynamically allocated memory using 'delete' for single objects and 'delete[]' for arrays.

13. What is the correct way to use 'new' and 'delete' for dynamic memory allocation of an object in C++?

a) MyClass* obj = new MyClass(); delete obj;

b) MyClass obj = new MyClass(); delete obj;

c) MyClass* obj = new MyClass(); delete[] obj;

d) MyClass* obj = new MyClass[1]; delete obj;

Answer:

a) MyClass* obj = new MyClass(); delete obj;

Explanation:

The correct way is to use 'new' to allocate memory for an object and 'delete' to free that memory.

14. How do you check if memory allocation by 'new' was successful in C++?

a) Checking if the pointer is null

b) Using the 'isAllocated' function

c) Catching an exception

d) Both a) and c)

Answer:

d) Both a) and c)

Explanation:

In modern C++, memory allocation failure by 'new' throws a bad_alloc exception. However, checking if the pointer is null is a good practice for older C++ code or custom memory allocation.

15. What is the initial value of dynamically allocated memory in C++?

a) 0

b) 1

c) Null

d) Indeterminate

Answer:

d) Indeterminate

Explanation:

The initial value of dynamically allocated memory in C++ is indeterminate unless explicitly initialized. It may contain garbage values.

16. What happens when 'new' fails to allocate memory in C++?

a) The program continues execution

b) It returns a null pointer

c) It throws a bad_alloc exception

d) The program terminates immediately

Answer:

c) It throws a bad_alloc exception

Explanation:

In standard C++, failing to allocate memory using 'new' results in throwing a bad_alloc exception.

17. How can you dynamically allocate memory for a two-dimensional array in C++?

a) int** arr = new int[rows][cols];

b) int* arr = new int[rows][cols];

c) int** arr = new int*[rows]; for(int i = 0; i < rows; i++) arr[i] = new int[cols];

d) int* arr = new int*(rows, cols);

Answer:

c) int** arr = new int*[rows]; for(int i = 0; i < rows; i++) arr[i] = new int[cols];

Explanation:

For a two-dimensional array, first allocate an array of pointers, then for each pointer, allocate an array of integers.

18. What is RAII in the context of C++ memory management?

a) Resource Allocation Is Initialization

b) Random Access of Independent Indexes

c) Release After Immediate Initialization

d) Resource Allocation In Iteration

Answer:

a) Resource Allocation Is Initialization

Explanation:

RAII (Resource Allocation Is Initialization) is a programming concept in C++ where resources are tied to object lifetimes, ensuring that resources such as memory are properly released when objects go out of scope.

19. What is the advantage of smart pointers over raw pointers in C++ for memory management?

a) Smart pointers are faster than raw pointers

b) Smart pointers provide automatic memory management

c) Smart pointers can store more types of data

d) Smart pointers use less memory

Answer:

b) Smart pointers provide automatic memory management

Explanation:

Smart pointers, such as unique_ptr and shared_ptr, provide automatic memory management to ensure that memory is properly freed when no longer needed, helping to prevent memory leaks.

20. What is the output of the following C++ code?

int* ptr = new int(10);
   cout << ptr;

a) 10

b) The memory address stored in ptr

c) 0

d) Error

Answer:

b) The memory address stored in ptr

Explanation:

The code will output the memory address stored in the pointer 'ptr', not the value it points to (which would be obtained with *ptr).