Bihar STET C++ Notes with Questions Answer

Part 1: High-Yield Revision Notes (Quick Theory)

1. Fundamentals of Object-Oriented Programming (OOPs)

OOPs is a programming paradigm that models real-world entities using objects.

• Class: A user-defined data type that binds data members (variables) and member functions (methods) into a single unit. It acts as a blueprint or template.

• Object: An instance of a class. It is a dynamic real-world entity that allocates memory when created.

• 4 Pillars of OOPs:

  1. Encapsulation: Wrapping data members and functions into a single unit (class). Helps achieve data hiding through private access modifiers.

  2. Abstraction: Hiding complex internal implementation details and displaying only essential features to the user (achieved using Abstract Classes and Interfaces).

  3. Inheritance: The mechanism by which an existing class (Base Class) allows a new class (Derived Class) to acquire its properties and behaviors, promoting code reusability.

  4. Polymorphism: The ability of a message or function call to exhibit different behaviors based on context ("One interface, multiple implementations").

2. Access Modifiers & Class Scope

Access modifiers dictate the accessibility of class members within or outside the class scope:

• Private (private): Members are accessible only within the class itself (Default access modifier for C++ classes).

• Protected (protected): Members are accessible inside the class and its derived (child) classes, but hidden from the outside world.

• Public (public): Members are accessible from anywhere in the program.

3. Constructors & Destructors

• Constructor: A special member function automatically executed when an object is instantiated. It shares the exact same name as the class and has no return type (not even void).

  • Default Constructor: Takes no arguments.

  • Parameterized Constructor: Takes arguments to initialize custom values during object creation.

  • Copy Constructor: Initializes an object using values from an existing object of the same class (Syntax: ClassName(const ClassName &obj)).

• Destructor: Automatically executes when an object goes out of scope to release allocated memory. It uses the exact same name as the class, preceded by a tilde symbol (~ClassName()). It takes no parameters and cannot be overloaded.

4. Inheritance & Access Visibility

                       Inheritance Types in C++
                                  |
    +-----------+-----------+-----+-----+-----------+
    |           |           |           |           |
 Single     Multiple   Multilevel    Hierarchical  Hybrid

Member Access Visibility Under Inheritance Modes:

Diamond Problem: Occurs in Multiple Inheritance when two parent classes inherit from the same base class, causing ambiguity in the derived class. Resolved using virtual base classes.

5. Polymorphism & Virtual Functions

Polymorphism is broadly categorized into two types:

1. Compile-time (Static) Polymorphism: Solved at compile time via Early / Static Binding.

   • Function Overloading: Multiple functions in the same scope with the same name but different parameter lists (type, count, or order).

   • Operator Overloading: Redefining existing C++ operators for user-defined types (Operators that cannot be overloaded: ., ::, ?:, sizeof, .*).

2. Run-time (Dynamic) Polymorphism: Solved at run time via Late / Dynamic Binding.

   • Function Overriding: Redefining a base class function in a derived class using the virtual keyword.

   • Pure Virtual Function: A function with no implementation body in the base class (Syntax: virtual void display() = 0;).

   • Abstract Class: A class containing at least one Pure Virtual Function. It cannot be instantiated (objects cannot be created).

6. Dynamic Memory Allocation & Pointers

• new Operator: Dynamically allocates memory on the Heap.

• delete Operator: Deallocates memory previously allocated on the Heap (e.g., delete ptr; or delete[] arr;).

• this Pointer: An implicit pointer available inside non-static member functions pointing directly to the invoking object's memory address.

• Friend Function: A non-member function granted explicit access to a class's private and protected members using the friend keyword.

Part 2: Top 35 Important MCQs (With Solutions)

1. What is the default access modifier for members in a C++ class?

   • Answer: private (Note: Default access in a C++ struct is public).

2. Who created the C++ programming language?

   • Answer: Bjarne Stroustrup (AT&T Bell Labs, 1979).

3. Which OOP principle is primarily used to achieve Data Hiding?

   • Answer: Encapsulation

4. A class containing at least one Pure Virtual Function is called an:

   • Answer: Abstract Class

5. Which of the following is the correct syntax for a Pure Virtual Function in C++?

   • Answer: virtual void display() = 0;

6. What is the return type of a Constructor in C++?

   • Answer: Constructors do not have any return type (not even void).

7. Which symbol precedes the class name to declare a Destructor?

   • Answer: Tilde symbol (~)

8. What is the standard parameter format for a Copy Constructor in C++?

   • Answer: Pass by reference with const (e.g., ClassName(const ClassName &obj)).

9. When a single derived class inherits directly from two or more base classes, the inheritance is called:

   • Answer: Multiple Inheritance

10. Which keyword is used to resolve the 'Diamond Problem' ambiguity in Multiple Inheritance?

    • Answer: virtual (Virtual Base Class)

11. Run-time Polymorphism (Dynamic Binding) is achieved in C++ using:

    • Answer: Virtual Functions (Function Overriding)

12. Which of the following is an example of Compile-time Polymorphism?

    • Answer: Function Overloading and Operator Overloading

13. Which of the following C++ operators CANNOT be overloaded?

    • Answer: Scope Resolution Operator (::), Sizeof (sizeof), Member Access Operator (.), Ternary Operator (?:)

14. Which operator is used to allocate memory dynamically on the heap in C++?

    • Answer: new operator

15. What is the correct syntax to free memory dynamically allocated for an array in C++?

    • Answer: delete[] ptr;

16. Which implicit pointer holds the address of the currently invoking object?

    • Answer: this pointer

17. Which function can access the private and protected members of a class despite not being a member function?

    • Answer: Friend Function (declared using the friend keyword)

18. Function Overloading resolution is based on differences in the function's:

    • Answer: Function Signature (parameter list types, order, or number). Return type alone is not sufficient.

19. Which header file must be included for standard input and output stream operations in C++?

    • Answer:

20. What are cout and cin in C++?

    • Answer: Pre-defined Objects (cout is an instance of ostream, cin is an instance of istream).

21. Protected members of a Base Class become private in a Derived Class under which inheritance mode?

    • Answer: Private Inheritance (private)

22. Redefining a Base Class function in a Derived Class with the exact same signature is known as:

    • Answer: Function Overriding

23. Why should a Base Class destructor be declared as virtual when using polymorphic behavior?

    • Answer: To ensure the Derived Class destructor executes first, preventing memory leaks during dynamic object deletion.

24. Templates in C++ represent which programming paradigm?

    • Answer: Generic Programming (Writing type-independent reusable code)

25. Which three keywords form the structure of Exception Handling in C++?

    • Answer: try, catch, and throw

26. What mechanism does the C++ compiler use internally to resolve Virtual Function calls dynamically?

    • Answer: Virtual Method Table (vtable) and vptr pointer.

27. How many Destructors can a single class possess?

    • Answer: Exactly ONE (Destructors cannot be overloaded).

28. What is the primary operational difference between a struct and a class in C++?

    • Answer: Members of a struct are public by default, whereas members of a class are private by default.

29. Which statement is true regarding Static Member Variables in C++?

    • Answer: A single copy is created and shared across all instantiated objects of that class.

30. Static Member Functions in C++ can directly access:

    • Answer: Only static data members and other static member functions (this pointer is unavailable).

31. What does the term "Class Instantiation" mean?

    • Answer: Creating an Object of that class.

32. Which C++ stream class is specifically used to perform file output (write) operations?

    • Answer: ofstream

33. What is the primary function of the Scope Resolution Operator (::)?

    • Answer: Accessing global variables or defining member functions outside the class declaration.

34. Every C++ program begins its execution from which function?

    • Answer: main() function

35. Early binding (Static Binding) takes place during:

    • Answer: Compile time