OOPs for Interviews

Jun 24, 2024

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Object-Oriented Programming (OOPs) from Zero to Advanced for Interviews

Introduction

  • Objective: Comprehensive coverage of OOPs from zero to advanced level, specifically tailored for interviews and college exams.
  • Importance: Essential for placements, internships, and understanding programming deeply.

Basics of Object-Oriented Programming

Key Concepts

  • Object-Oriented Programming (OOPs): Writing code in a better, organized way. Not always compulsory but beneficial in real-life scenarios, especially in organization-level projects.
  • Implementation Examples in C++: Using vector, string, stack libraries, etc.

Important Terms

  • Class: Blueprint of objects, defining how objects should look.
  • Object: Representation of real-world entities in code.

Example of Classes and Objects in C++

  • Defining Classes: Properties and methods within a class (e.g., Teacher class with properties like name, department, salary).
  • Creating Objects: Using the class_name object_name syntax.

Access Modifiers

Types of Access Modifiers

  • Private: Accessible only within the class. By default, everything is private in C++ classes.
  • Public: Accessible from anywhere in the program.
  • Protected: Used mainly with inheritance; accessible within the class and its derivatives.

Constructor and Destructor

Constructor

  • Special Functions: Automatically invoked when an object is created. Initializes object properties.
  • Types: Default Constructor, Parameterized Constructor, Copy Constructor.
  • This Pointer: Refers to the current object instance.

Destructor

  • Purpose: Deallocate memory; inverse of the constructor.
  • Specialty: Automatically invoked when an object goes out of scope.

Inheritance in OOPs

Key Points

  • Definition: Mechanism where one class inherits properties and methods from another class.
  • Types: Single Inheritance, Multi-level Inheritance, Multiple Inheritance, Hierarchical Inheritance, Hybrid Inheritance.
  • Practical Examples: Defining classes like Person, Teacher, Student, and demonstrating inheritance among them.

Polymorphism in OOPs

Types of Polymorphism

  • Compile-Time Polymorphism: Examples include function overloading, operator overloading, constructor overloading. Resolved during compilation.
  • Run-Time Polymorphism: Achieved through function overriding and virtual functions. Resolved during runtime.

Function Overloading vs. Overriding

  • Overloading: Same function name, different parameters within the same class.
  • Overriding: Same function name, same parameters in both parent and child classes, with different implementations.

Advanced OOPs Concepts

Abstraction

  • Purpose: Hiding unnecessary details and showing important ones. Implemented using access modifiers and abstract classes.
  • Abstract Classes and Pure Virtual Functions: Used as blueprints for other classes; cannot instantiate abstract classes.

Static Keyword

  • Static Variables/Methods: Shared among all instances of a class. Lifetime of static variables is the entire program.
  • Static Objects: Persist till the end of the program.

Conclusion

  • Preparation for Interviews: Key concepts covered for thorough understanding. Emphasis on understanding and application.
  • Next Steps: Solve MCQs based on OOPs concepts, create practical examples, and review definitions.

All the best for your internship and placement interviews!