C++ Programming: Functions & OOP

1. Functions in C++

A function is a block of code that performs a specific task. Functions allow us to reuse code: we define the code once and call it whenever it is needed.

#include <iostream>
using namespace std;

void myFunction() {
  int x = 2;
  int y = 5;
  cout << "Sum of the two numbers is: " << x + y << endl;
}

int main() {
  myFunction(); // Calling the function
  return 0;
}

Output: Sum of the two numbers is: 7

2. OOP Concepts in C++

OOP (Object-Oriented Programming) is a paradigm that uses Classes (blueprints) and Objects (instances). It provides a clear structure and helps keep code organized.

Note: These concepts apply to C++, as standard C does not support classes.

#include <iostream>
#include <string> // Required for string variables
using namespace std;

class MyClass {       // The class
  public:             // Access specifier
    int myNum;        // Attribute (int variable)
    string myString;  // Attribute (string variable)
};

int main() {
  MyClass myObj;      // Create an object of MyClass

  // Access attributes and set values
  myObj.myNum = 15;
  myObj.myString = "Some text";

  // Print values
  cout << myObj.myNum << "\n";
  cout << myObj.myString << endl;
  
  return 0;
}

Output: 15
Some text

3. Methods in C++

Methods are functions that belong to a class. They define the behavior of the objects created from that class.

#include <iostream>
using namespace std;

class MyClass {
  public:
    void myMethod() {   // Method defined inside the class
      cout << "Hello World!";
    }
};

int main() {
  MyClass myObj;     // Create an object of MyClass
  myObj.myMethod();  // Call the method
  return 0;
}

Output: Hello World!

4. Parameters and Scope Resolution

Parameters allow you to pass data into methods. You can also define methods outside the class using the scope resolution operator (::).

#include <iostream>
using namespace std;

class Thermometer {
  public:
    // Method declaration
    int convertToCelsius(int fahrenheit);
};

// Method definition outside the class
int Thermometer::convertToCelsius(int fahrenheit) {
  return 5 * (fahrenheit - 32) / 9;
}

int main() {
  Thermometer myObj;
  // Passing -40 as a parameter
  cout << "Result: " << myObj.convertToCelsius(-40); 
  return 0;
}

Output: Result: -40