LLD & OOP Study Notes
Object-oriented design, SOLID, patterns, and machine coding.
FreeLow-Level Design Study Note PDF
A beginner-friendly Low-Level Design PDF guide covering four important LLD interview systems: Parking Lot, Food Delivery, Library System, and Splitwise. This guide explains how real-world systems are broken into entities, classes, relationships, responsibilities, workflows, edge cases, and design trade-offs. It is designed for beginner to intermediate developers who want to build a strong foundation in LLD without getting overwhelmed by UML-heavy theory. Topics Covered 1. Design a Parking Lot - Vehicle types, spots, tickets, entry/exit gates, pricing, availability, and class design. 2. Design a Food Delivery System - Users, restaurants, menus, carts, orders, delivery partners, payments, and order states. 3. Design a Library System - Books, book copies, members, borrowing, returns, reservations, fines, and search. 4. Design Splitwise - Users, groups, expenses, equal/exact/percentage splits, balances, settlements, and simplification. 5. LLD Interview Approach - Requirement clarification, entity identification, class relationships, edge cases, and trade-offs. What You Will Get 11-page detailed PDF guide Four common LLD interview problems Entity and class breakdowns Real-world workflows Design tables and examples Interview-focused revision notes Best For Software engineering students, backend developers, full-stack developers, LLD interview aspirants, developers learning object-oriented design, and machine coding round candidates.
FreeOOP Concepts And SOLID Study Note PDF
A beginner-friendly OOP and SOLID principles PDF guide covering object-oriented programming fundamentals along with the five SOLID design principles. This guide connects OOP concepts with clean code and maintainable design using real-world examples, code snippets, tables, and interview-style explanations. It is perfect for developers who want to move beyond basic OOP and understand how professional software is structured for flexibility, testing, reuse, and long-term maintenance. Topics Covered 1. OOP Fundamentals - Classes, objects, abstraction, encapsulation, inheritance, polymorphism, and composition. 2. Single Responsibility Principle - Why a class should have one clear reason to change. 3. Open/Closed Principle - How to make code open for extension but closed for modification. 4. Liskov Substitution Principle - Safe inheritance and how subclasses should behave like parent types. 5. Interface Segregation Principle - Why small focused interfaces are better than large forced interfaces. 6. Dependency Inversion Principle - Abstractions, dependency injection, loose coupling, and testable code. What You Will Get 10-page detailed PDF guide OOP plus SOLID concepts Beginner-friendly explanations Real-life examples and code snippets Interview-focused Q&A and revision notes Best For Software engineering students, backend developers, full-stack developers, Java/C#/C++/Python/TypeScript learners, and developers preparing for LLD interviews.
FreeOOP Concepts Study Note PDF
A beginner-friendly Object-Oriented Programming PDF guide covering the core OOP concepts asked in programming and software engineering interviews. This study note explains classes, objects, encapsulation, abstraction, inheritance, polymorphism, and composition using simple examples and real-world analogies. It is designed for beginner to intermediate developers who want to understand OOP clearly before moving into design patterns, low-level design, machine coding, and system design interviews. Topics Covered 1. Classes And Objects - Learn how classes act as blueprints and objects represent real instances with state and behavior. 2. Encapsulation - Understand data hiding, access control, validation, and keeping object internals safe. 3. Abstraction - Learn how to expose only necessary behavior while hiding implementation details. 4. Inheritance - Understand parent-child relationships, code reuse, and when inheritance can become risky. 5. Polymorphism - Learn method overriding, interface-based design, and runtime flexibility. 6. Composition - Understand why composition is often preferred over inheritance in real-world design. What You Will Get 9-page detailed PDF guide Simple OOP explanations Real-life examples Interview-focused tables Code examples and revision-friendly notes Best For Programming beginners, software engineering students, Java/C++/Python/JavaScript learners, tech interview aspirants, and developers preparing for OOP rounds.