OOP Review

📘 OOP Review (Object-Oriented Programming)

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🔹 1. What is OOP?

Object-Oriented Programming (OOP) is a programming approach where software is designed using objects, which combine data (attributes) and behavior (methods).

👉 Simple idea: Programs are built by modeling real-world entities like Car, Student, BankAccount as objects.

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🔹 2. Basic Building Blocks

🔸 2.1 Class

• A blueprint/template for creating objects
• Defines attributes and methods

Example:

Class: Student
Attributes: name, rollNo
Methods: study(), attendClass()

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🔸 2.2 Object

• An instance of a class
• Represents a real entity

Example:

Student s1 = new Student();

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🔸 2.3 Attributes & Methods

Component	Meaning
Attributes	Data (variables)
Methods	Functions (behavior)

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🔹 3. Four Pillars of OOP ⭐

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🔸 3.1 Abstraction

• Show only important details
• Hide complex implementation

Example: Using a mobile phone without knowing internal circuits

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🔸 3.2 Encapsulation

• Wrapping data + methods together
• Restrict direct access to data

Example:

private balance;
public deposit();

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🔸 3.3 Inheritance

• One class inherits properties of another

Example:

Animal → Dog

Benefit: Code reuse

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🔸 3.4 Polymorphism

• One function behaves differently in different situations

Types:

• Method Overloading
• Method Overriding

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🔹 4. Important Concepts

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🔸 4.1 Message Passing

Objects communicate by calling each other's methods

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🔸 4.2 Dynamic Binding

Method call is resolved at runtime

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🔸 4.3 Association Relationships

Type	Meaning
Association	General relation
Aggregation	Weak ownership
Composition	Strong ownership

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🔸 4.4 Constructor

• Special method used to initialize objects

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🔸 4.5 Destructor (in some languages)

• Used to free memory/resources

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🔹 5. Advantages of OOP

• Reusability
• Security (data hiding)
• Easy maintenance
• Real-world modeling
• Scalability

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🔹 6. Simple Example

👉 Bank System

Class:

BankAccount
- balance
+ deposit()
+ withdraw()

Object:

acc1.deposit(1000)

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🔹 7. OOP vs Procedural Programming

Feature	OOP	Procedural
Focus	Objects	Functions
Data Security	High	Low
Reusability	High	Limited

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🔹 8. Key Rules to Remember

• Use classes to model real-world objects
• Keep data private (encapsulation)
• Use inheritance for reuse
• Apply polymorphism for flexibility

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🔹 9. Likely Exam Questions

1. What is OOP? Explain with example.
2. Define class and object.
3. Explain the four pillars of OOP.
4. What is encapsulation and why is it important?
5. Describe inheritance with types.
6. What is polymorphism? Give examples.
7. Differentiate OOP and procedural programming.
8. What is dynamic binding?
9. Explain aggregation vs composition.
10. What are advantages of OOP?

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🔹 10. Quick Revision Summary 🧠

• OOP = Objects + Classes

• Class → Blueprint

• Object → Instance

• 4 Pillars:

  • Abstraction
  • Encapsulation
  • Inheritance
  • Polymorphism

👉 Shortcut Trick: "AEIP" (Abstraction, Encapsulation, Inheritance, Polymorphism)

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