1. What is Object-Oriented Programming (OOP)?
OOP is a programming model that organizes software design around data, or objects, rather than functions and logic. An object is a unit that contains data (attributes) and methods (functions) that work on the data. This structure allows complex programs to be more manageable and modular.
2. Why is OOP beneficial?
OOP helps in creating modular, reusable, and maintainable code. Key benefits include:
- Improved Code Organization: OOP models closely relate to real-world objects, improving understanding.
- Encapsulation: Groups data and methods, protecting data and allowing easy maintenance.
- Ideal for Complex Applications: Particularly useful for large, complex applications that require scalability.
3. What is a Class?
A class is a blueprint for creating objects. It defines attributes (data) and methods (behaviors) that the objects created from the class will have.
4. What is an Object?
An object is an instance of a class, containing data and behavior as defined by the class. Objects are individual examples created from classes.
5. What are the main features of OOP?
OOP is built on four main principles:
- Encapsulation: Bundling data with methods that operate on it.
- Abstraction: Showing only relevant data and hiding unnecessary details.
- Polymorphism: Allowing methods or functions to operate in different ways depending on the context.
- Inheritance: Creating new classes from existing ones, reusing code and functionality.
6. What is Encapsulation?
Encapsulation restricts direct access to an object’s data by combining the data and methods within a single unit. It protects object integrity by only allowing manipulation through well-defined methods.
7. What is Abstraction?
Abstraction hides complex details and only shows the essential parts of an object. For example, a car dashboard abstracts the internal mechanics, showing only what’s necessary for the driver.
8. What is Polymorphism?
Polymorphism means “many forms” and allows a method or function to operate in different ways depending on the object context. It is typically achieved through:
- Compile-Time Polymorphism (e.g., method overloading)
- Runtime Polymorphism (e.g., method overriding)
9. What is Inheritance?
Inheritance allows one class (subclass) to inherit properties and methods from another class (superclass), promoting code reuse.
10. What are Access Specifiers, and why are they important?
Access specifiers control access to class members. Common specifiers include:
- Public: Accessible from outside the class.
- Private: Accessible only within the class.
- Protected: Accessible within the class and its subclasses.
11. What are the advantages and disadvantages of OOP?
Advantages:
- Promotes code reusability and modular design.
- Easier maintenance with encapsulation.
- Enhanced data security.
Disadvantages:
- Requires careful planning and a mindset shift to object thinking.
- Can increase code complexity and length.
12. What is an Abstract Class?
An abstract class is a class intended for inheritance that cannot be instantiated on its own. It may contain abstract methods without implementations, requiring derived classes to provide specifics.
13. Difference between Structured and Object-Oriented Programming?
- OOP: Organizes code around objects and their interactions, using encapsulation, inheritance, and polymorphism.
- Structured Programming: Organizes code around functions and sequences, using a top-down approach without encapsulation.
14. Common OOP Languages?
Popular OOP languages include:
- C++
- Java
- Python
- C#
- Ruby
15. Types of Polymorphism?
Polymorphism is of two main types:
- Compile-Time: Method overloading and operator overloading.
- Runtime: Method overriding.
16. What is the difference between Overloading and Overriding?
- Overloading: Having multiple methods with the same name but different parameters within the same class (compile-time).
- Overriding: Redefining a method from a parent class in a subclass to change its behavior (runtime).
17. Limitations of Inheritance?
Inheritance can create tightly coupled classes, increasing dependencies. It can make changes more challenging and may lead to complex, unintended behavior if not managed well.
18. Types of Inheritance?
Types include:
- Single Inheritance: One class inherits from one superclass.
- Multiple Inheritance: One class inherits from multiple superclasses.
- Multilevel Inheritance: Chain of inheritance, where a class inherits from a derived class.
- Hierarchical Inheritance: Multiple classes inherit from a single superclass.
- Hybrid Inheritance: Combination of different types of inheritance.
19. What is an Interface?
An interface defines methods that must be implemented by classes but doesn’t provide their implementations.
20. How does an Abstract Class differ from an Interface?
- Abstract Class: Can include both abstract and non-abstract methods and variables.
- Interface: Only includes abstract methods, and all fields are static and final.
21. Do classes occupy memory?
Classes do not occupy memory by themselves; memory is allocated only when an object of the class is created.
22. Do we always need to create an object from a class?
No. Classes with static methods can be used without creating an object.
23. Difference between Structure and Class in C++?
The main difference is access control. In a structure, members are public by default, while in a class, they are private.
24. What is a Constructor?
A constructor is a method that initializes an object. It has the same name as the class and sets initial values for the object’s data members.
25. Types of Constructors in C++?
- Default Constructor: No arguments.
- Parameterized Constructor: Takes arguments.
- Copy Constructor: Initializes an object using another object of the same class.
26. What is a Destructor?
A destructor is called when an object goes out of scope or is deleted, allowing for resource cleanup.
27. Can Constructors be Overloaded?
Yes, constructors can be overloaded by defining multiple constructors with different parameters.
28. Can Destructors be Overloaded?
No, destructors cannot be overloaded. Only one destructor is allowed per class.
29. What is a Virtual Function?
A virtual function allows derived classes to override a method from the base class. It helps achieve runtime polymorphism.
30. What is a Pure Virtual Function?
A pure virtual function is a function with no implementation in the base class and must be overridden in derived classes. It makes a class abstract and intended only for inheritance.