Object-Oriented Programming (OOPs) in C++

1. Need for OOP

As software complexity grows, procedural programming (like in C) becomes harder to manage. OOP allows:

• Better Code Organization: Breaks large systems into smaller, manageable parts.
• Modularity: Reusable code through objects and classes.
• Maintenance: Easier to update and maintain code over time.

Example:

In a large system managing vehicles:

class Car {
    public:
        string brand;
        void honk() {
            cout << "Beep Beep!";
        }
};
 
Car myCar;
myCar.brand = "Toyota";
myCar.honk(); // Output: Beep Beep!

2. Object-Oriented Approach

OOP focuses on:

• Objects: Entities that encapsulate data and behavior.
• Classes: Blueprints for creating objects.
• Interaction: Objects interact with one another to perform tasks.

3. Characteristics of OOP Languages

3.1. Objects

Objects represent real-world entities.

class Dog {
    public:
        string name;
        void bark() {
            cout << "Woof Woof!";
        }
};
 
Dog myDog;
myDog.name = "Buddy";
myDog.bark(); // Output: Woof Woof!

3.2. Classes

Classes define properties and behaviors.

class Animal {
    public:
        string name;
        void speak() {
            cout << name << " is making a sound.";
        }
};

3.3. Inheritance

Inheritance allows a new class to inherit properties from an existing class, promoting code reuse.

class Vehicle {
    public:
        void start() {
            cout << "Vehicle started.";
        }
};
 
class Bike : public Vehicle {
    public:
        void ride() {
            cout << "Bike is riding.";
        }
};
 
Bike myBike;
myBike.start(); // Output: Vehicle started.

3.4. Reusability

OOP allows code to be reused across different projects and scenarios through inheritance and composition.

3.5. Polymorphism

Polymorphism lets functions or methods have different behavior depending on the object.

class Shape {
    public:
        virtual void draw() {
            cout << "Drawing a shape.";
        }
};
 
class Circle : public Shape {
    public:
        void draw() override {
            cout << "Drawing a circle.";
        }
};
 
Shape* shape = new Circle();
shape->draw(); // Output: Drawing a circle.

3.6. Overloading

Overloading enables multiple functions with the same name to work differently depending on their parameters.

int add(int a, int b) {
    return a + b;
}
 
double add(double a, double b) {
    return a + b;
}

4. Advantages of OOP

• Modularity: Divides the program into objects and classes.
• Maintainability: Easier to manage code over time.
• Reusability: Promotes the reuse of code in different parts of the program.
• Scalability: Can grow easily by adding new classes and methods.

5. Relationship Between C and C++

• C: Procedural language, focuses on functions and step-by-step execution.
• C++: Extends C by adding OOP principles, allowing the creation of objects and classes, making the program more modular and manageable.

Programming Basics in C++

1. Basic Program Construction

A basic C++ program consists of:

• Header Files: These are libraries that provide functions to the program.
• Main Function: The entry point where the program execution starts.

Example:

#include <iostream>
using namespace std;
 
int main() {
    cout << "Hello, World!";
    return 0;
}

2. Output Using cout

cout is used to display output on the console:

cout << "Welcome to C++ programming!";

3. Preprocessor Directives

Preprocessor directives are commands that are processed before the compilation of code. Commonly used ones include:

#include <iostream>

4. Comments

• Single-line comments: // This is a comment
• Multi-line comments: /* This is a multi-line comment */

5. Integer and Character Variables

Variables store data that the program manipulates.

int num = 10;
char letter = 'A';

6. Input Using cin

cin is used to take input from the user:

int age;
cin >> age;

7. Type bool

The bool type holds two values: true and false.

bool isAvailable = true;

8. setw Manipulator

The setw manipulator sets the width of the output field.

#include <iomanip>
cout << setw(10) << "Hello";

9. Type float

A float variable stores decimal numbers.

float pi = 3.14;

10. Type Conversion

Type conversion converts one type of data to another.

int a = 5;
float b = static_cast<float>(a); // Converts int to float

11. Arithmetic Operators

Arithmetic operators are used to perform mathematical calculations:

• +, -, *, /, %

12. Relational Operators

These operators compare values:

• ==, !=, <, >, <=, >=

13. Logical Operators

Logical operators combine two or more conditions:

• && (AND), || (OR), ! (NOT)

Diagrams

OOP Characteristics

Difference Between C and C++