OOPS (Object-Oriented Programming) - Zero to Advanced Lecture

Introduction

• Covers entire OOPS concepts from basic to advanced level.
• Focus on preparing for placement and internship interviews.
• Important for understanding programming and performing well in technical interviews.

Key Benefits

• Strong understanding of OOPS benefits interviews and programming skills in companies.
• Comprehensive coverage of theory, definitions, examples, and coding demonstrations.
• Ends with 30 MCQs to strengthen understanding.

Objects and Classes

• Objects: Real-world entities (e.g., pen, laptop, phone). Converted into objects in C++ code.
• Class: Blueprint for objects. Defines how objects should look and function.
• Example: Toyota car designs - a standardized blueprint for different cars.

Code Example

• Teacher System

  • Properties: Name, Department, Subject, Salary.
  • Functions: Change Department, Calculate Salary Tax.
  • Convert these properties and functions into a class and create multiple objects.
  class Teacher { std::string name; std::string department; std::string subject; double salary; public: void setSalary(double s) { salary = s; } double getSalary() { return salary; } }; Teacher t1; t1.name = "John"; t1.department = "CS"; t1.subject = "C++"; t1.setSalary(25000); std::cout << t1.getSalary();

Encapsulation

• Wrapping data and functions into a single unit (Class).
• Data hiding through private and public access specifiers.
• Example: Bank system to hide sensitive information like balance and password.

Constructor and Destructor

• Constructor: Initializes object when created. No return type, same name as class.

• Destructor: Deallocates memory when object is destroyed. No arguments, same name with ~.

  class Student { public: Student() { std::cout << "Constructor"; } ~Student() { std::cout << "Destructor"; } }; Student s;

Inheritance

• Deriving new classes from existing ones.

• Promotes code reusability.

• Types: Single, Multi-level, Multiple, Hierarchical, Hybrid.

  class Person { public: std::string name; int age; }; class Student : public Person { public: int rollNo; };

Polymorphism

• Ability of a function or object to take multiple forms.

• Types: Compile-time (Function Overloading, Operator Overloading), Run-time (Virtual Functions).

  class Print { public: void show(int i) { std::cout << i; } void show(char c) { std::cout << c; } }; Print p; p.show(5); // Prints int p.show('a'); // Prints char

Abstraction

• Hiding unnecessary details and showing essential features.

• Implemented using classes and access specifiers.

  • Example: Abstract classes with virtual functions.
  class Shape { public: virtual void draw() = 0; // Pure virtual function }; class Circle : public Shape { public: void draw() { std::cout << "Drawing Circle"; } }; Circle c; c.draw();

Static Keyword

• Static Variables: Persistent across function calls. Lifetime of the program.

• Static Functions: Shared among all objects of the class.

  class Example { public: static int x; }; int Example::x = 0;

Summary

• Understanding OOPS is essential for performing well in technical interviews and programming in a corporate environment.
• Focus on encapsulation, inheritance, polymorphism, and abstraction for a strong grasp.
• Practice with MCQs and real-life implementation examples.