Welcome to our engaging and informative blog post titled "C++ Classes and Objects Quiz - MCQ Questions and Answers." This post is specially designed for learners, enthusiasts, and professionals who are eager to test and expand their knowledge of C++'s foundational concepts: classes and objects.
Through a series of 20 thought-provoking multiple-choice questions, this quiz offers a comprehensive review of how classes and objects operate in C++, a cornerstone of object-oriented programming. Whether you're studying for a test, preparing for interviews, or just refreshing your understanding, this quiz is a perfect tool to assess and enhance your grasp of these essential C++ concepts. Get ready to challenge your skills and deepen your programming insights with this fun and educational quiz!
1. What is a class in C++?
a) A data type defined by the user
b) A blueprint for creating objects
c) A collection of functions
d) A container for variables
Answer:
b) A blueprint for creating objects
Explanation:
In C++, a class is a blueprint or template for creating objects. It defines properties (data members) and behaviors (member functions or methods) of the objects.
2. How do you create an object in C++?
a) className objectName;
b) objectName className;
c) className::objectName;
d) new className;
Answer:
a) className objectName;
Explanation:
An object in C++ is created by specifying the class name followed by the object name.
3. What are member functions in a C++ class?
a) Functions defined outside the class
b) Functions that operate on class data
c) Independent functions
d) Functions that return class objects
Answer:
b) Functions that operate on class data
Explanation:
Member functions are functions that are defined within a class and are used to access and manipulate the data members of the class.
4. What is encapsulation in C++?
a) The process of combining data and functions into a single unit called class
b) The ability of an object to take many forms
c) The process of inheriting properties from another class
d) A method of data manipulation
Answer:
a) The process of combining data and functions into a single unit called class
Explanation:
Encapsulation in C++ is the concept of bundling data (variables) and methods (functions) that work on the data into a single unit, or class, to hide the details and complexity from the user.
5. What is a constructor in C++?
a) A special function used to initialize objects of its class
b) A function that destroys an object
c) A normal function declared inside a class
d) A static member function of a class
Answer:
a) A special function used to initialize objects of its class
Explanation:
A constructor in C++ is a special member function that is automatically called when an object of the class is created. It is used to initialize the object's properties.
6. What is an object in C++?
a) A variable of a fundamental data type
b) An instance of a class
c) A function inside a class
d) A method of data manipulation
Answer:
b) An instance of a class
Explanation:
An object in C++ is an instance of a class. It is created from a class and represents a real-world entity with attributes (data members) and behaviors (member functions).
7. What is a destructor in C++?
a) A function that initializes an object
b) A special function that is called when an object goes out of scope
c) A member function that deletes an object
d) A static function that destroys all objects of a class
Answer:
b) A special function that is called when an object goes out of scope
Explanation:
A destructor in C++ is a special member function that is automatically called when an object goes out of scope or is explicitly deleted. It is used to release resources that the object may have acquired during its lifetime.
8. What is meant by 'overloading a constructor' in C++?
a) Defining multiple constructors with different sets of parameters
b) Increasing the efficiency of a constructor
c) Calling a constructor multiple times
d) Extending the functionality of a constructor
Answer:
a) Defining multiple constructors with different sets of parameters
Explanation:
Constructor overloading in C++ is the concept of having more than one constructor with different parameters in the same class, allowing objects of the class to be initialized in different ways.
9. How is a static member variable defined in a C++ class?
a) By using the 'static' keyword inside the class definition
b) By initializing the variable outside the class
c) By declaring the variable in the public section
d) By assigning the variable a constant value
Answer:
a) By using the 'static' keyword inside the class definition
Explanation:
A static member variable is declared within a class using the 'static' keyword. It is shared by all objects of the class and exists independently of any objects.
10. What is inheritance in C++?
a) Sharing data between classes
b) Deriving new classes from existing classes
c) Copying properties of one class into another
d) Changing the behavior of a function
Answer:
b) Deriving new classes from existing classes
Explanation:
Inheritance in C++ is a mechanism where a new class (derived class) inherits the properties and behavior of an existing class (base class). This allows for code reusability and hierarchical classification.
11. What are access specifiers in C++?
a) Keywords that set the access level of class members
b) Functions that determine how a class is accessed
c) Variables that specify the size of a class
d) Operators that manage class member access
Answer:
a) Keywords that set the access level of class members
Explanation:
Access specifiers in C++, such as public, private, and protected, determine the accessibility of class members from outside the class.
12. What is a copy constructor in C++?
a) A constructor that copies data from one object to another
b) A default constructor provided by the compiler
c) A constructor used to create a copy of a given object
d) A constructor that initializes an object from another object of the same class
Answer:
d) A constructor that initializes an object from another object of the same class
Explanation:
A copy constructor in C++ is a special constructor that initializes a new object from an existing object of the same class. It is used when an object is passed by value or returned from a function.
13. What is a friend function in C++?
a) A function that can only be called by another function
b) A member function of a class
c) A function that has access to private and protected members of the class
d) A function that is always static
Answer:
c) A function that has access to private and protected members of the class
Explanation:
A friend function in C++ is a function that is not a member of a class but has access to the class's private and protected members. It is declared using the 'friend' keyword in the class definition.
14. How do you define a member function of a class outside the class in C++?
a) returnType className::functionName(parameters) {body}
b) functionName::className(parameters) {body}
c) className returnType::functionName(parameters) {body}
a) returnType className::functionName(parameters) {body}
Explanation:
To define a member function outside the class, the function definition is preceded by className::, which indicates that the function belongs to the class.
15. What is polymorphism in C++?
a) The ability of a class to have multiple constructors
b) The ability of a function to perform different tasks based on the context
c) The capability of creating many objects from a single class
d) The feature of combining multiple classes into one
Answer:
b) The ability of a function to perform different tasks based on the context
Explanation:
Polymorphism in C++ refers to the ability of functions or operators to behave differently in different contexts, such as function overloading and operator overloading.
16. What is the use of the 'this' pointer in C++?
a) To store the address of the currently executing function
b) To pass an object as an argument to another function
c) To refer to the current object instance
d) To create a new object
Answer:
c) To refer to the current object instance
Explanation:
The 'this' pointer in C++ is a special pointer used within a class, which points to the current object instance. It is used to access the members of the object on which a member function is called.
17. How can a class member be hidden in C++?
a) By declaring it private
b) By using the 'hide' keyword
c) By defining it in another class
d) By not initializing it
Answer:
a) By declaring it private
Explanation:
In C++, class members can be hidden from outside access by declaring them private. This restricts their accessibility only to member functions of the same class.
18. What is operator overloading in C++?
a) Changing the way operators work in C++
b) Using an operator more than once in a program
c) Providing a new definition to an existing operator
d) Overloading a function based on its return type
Answer:
c) Providing a new definition to an existing operator
Explanation:
Operator overloading in C++ is a feature that allows operators to be redefined and used in different ways, depending on their operands. It enables operators to operate on user-defined types.
19. What is a virtual function in C++?
a) A function that exists only in virtual classes
b) A function that cannot be implemented
c) Member functions that are overridden in derived classes
d) Functions that are declared with the keyword 'virtual'
Answer:
d) Functions that are declared with the keyword 'virtual'
Explanation:
Virtual functions in C++ are member functions declared in the base class using the 'virtual' keyword and are meant to be overridden in derived classes. They enable runtime polymorphism.
20. What is a pure virtual function in C++?
a) A function that can only be called from a derived class
b) A virtual function that has no definition
c) A function that is defined in a base class and overridden in a derived class
d) A virtual function that is declared but not implemented
Answer:
d) A virtual function that is declared but not implemented
Explanation:
A pure virtual function in C++ is a virtual function that is declared in a base class but has no implementation in that class, typically represented with '= 0' in its declaration. It must be overridden in derived classes.
21. How do you define a constant member function in C++?
a) By using the const keyword after the member function's name
b) By using the constant keyword before the function's return type
c) By initializing all member variables as constants
d) By defining the function outside the class
Answer:
a) By using the const keyword after the member function's name
Explanation:
A constant member function is defined by placing the const keyword after the member function's parameter list. This specifies that the function does not modify the object on which it's called.
22. In C++, what is an abstract class?
a) A class designed only for serving as a base class
b) A class that has at least one pure virtual function
c) A class that cannot create instances
d) Both a) and b)
Answer:
d) Both a) and b)
Explanation:
An abstract class in C++ is a class that cannot be instantiated and is designed to be used as a base class. It contains at least one pure virtual function.
23. What is the role of a destructor in C++?
a) To allocate memory to objects
b) To initialize object members
c) To clean up resources used by an object
d) To create objects dynamically
Answer:
c) To clean up resources used by an object
Explanation:
The destructor in C++ is a special member function that is called automatically when an object is destroyed. It is used to release resources and perform cleanup tasks for the object.
24. How do you declare a member function that does not modify any class member in C++?
a) By using the static keyword
b) By declaring the function outside the class
c) By using the const keyword after the member function's declaration
d) By initializing all member variables in the function
Answer:
c) By using the const keyword after the member function's declaration
Explanation:
A member function that does not modify any class member variables is declared by adding the const keyword after the function's parameter list, indicating it's a constant member function.
25. What is the use of the static keyword with a member variable in a class in C++?
a) To make the variable constant
b) To share the variable among all instances of the class
c) To initialize the variable with zero
d) To make the variable private
Answer:
b) To share the variable among all instances of the class
Explanation:
A static member variable in a class is shared among all instances of the class. It means there is only one copy of the static member for the entire class, irrespective of the number of objects created.
26. What is method overloading in C++?
a) Creating multiple methods with different return types
b) Creating multiple methods with the same name but different parameters
c) Overriding a method of the base class in the derived class
d) Changing the way a method works in a derived class
Answer:
b) Creating multiple methods with the same name but different parameters
Explanation:
Method overloading in C++ is the process of creating multiple methods in the same scope with the same name but different parameters. It allows methods to perform differently based on the arguments passed.
27. What happens if a class has a private constructor in C++?
a) The class cannot be instantiated
b) The class can only create static objects
c) The constructor can only be called from member functions
d) The class can only be inherited
Answer:
a) The class cannot be instantiated
Explanation:
If a class has a private constructor, it cannot be instantiated from outside the class. This is often used in the Singleton design pattern to control object creation.
28. How do you access a static member variable of a class in C++?
a) Using the object of the class
b) Using the class name followed by the scope resolution operator (::)
c) Both a) and b)
d) By declaring the variable as public
Answer:
b) Using the class name followed by the scope resolution operator (::)
Explanation:
Static member variables in C++ are accessed using the class name followed by the scope resolution operator (::), without needing an object of the class.
29. What is an overloaded constructor in C++?
a) A constructor that can load objects of different classes
b) A constructor that is used for object copying
c) A constructor that has the same name as another constructor but different parameters
d) A constructor that is called multiple times
Answer:
c) A constructor that has the same name as another constructor but different parameters
Explanation:
An overloaded constructor in C++ refers to having more than one constructor with different sets of parameters within the same class.
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