What is Object-Oriented Programming (OOP)?
Why Interviewers Ask This
Foundational questions like this help interviewers calibrate the rest of the interview. A confident, accurate answer signals that you have solid OOP Concepts basics — a prerequisite for any developer role.
Answer
Object-Oriented Programming (OOP) is a programming paradigm that organizes software design around objects — instances of classes that combine data (attributes/fields) and behavior (methods/functions) into single, cohesive units. OOP emerged in the 1960s with Simula and became mainstream with Smalltalk, C++, Java, Python, and many modern languages. Core idea: instead of thinking about a program as a sequence of instructions (procedural), think of it as a collection of interacting objects, each responsible for its own data and behavior. This mirrors how we conceptualize the real world — a car has properties (color, speed) and behaviors (accelerate, brake). Four pillars: Encapsulation (data + behavior in one unit), Abstraction (hide complexity), Inheritance (reuse code), Polymorphism (one interface, many forms). Benefits: code reusability via inheritance and composition; modularity — changes in one class don't affect others; maintainability — easier to understand and modify; scalability — add new features by extending; real-world modeling — concepts map naturally to code. Contrast with procedural: procedural programs have data and procedures separately; OOP bundles them. OOP excels for large, complex systems with many interacting components. Pure OOP languages: Smalltalk, Ruby (everything is an object). Multi-paradigm: Python, Java, C++, C# — support OOP plus other paradigms.
Pro Tip
Back up your answer with a specific project or situation. Saying 'In my last OOP Concepts project, I used this when...' immediately makes your answer more credible and memorable.