📅 Date: Jan 7, 2026
🔥 Topic: Functions (Part 2): Parameters & Return Types

🔄 Sending & Receiving Data

Yesterday's function was static. Today, I learned how to make functions dynamic by passing data into them (Parameters) and getting results back (Return Values).

1️⃣ Parameters (Inputs)

These are variables inside the parentheses ( ) that accept values when the function is called.

2️⃣ Return Statement (Output)

Instead of printing the result, a function can throw the result back to main() using the return keyword.

💻 Day 7 Code: The Adder

Here is a function that takes two integers, adds them, and returns the result. 

#include <iostream>
using namespace std;

// Function that takes input and returns output
int addNumbers(int a, int b) {
    int sum = a + b;
    return sum; // Throwing value back
}

int main() {
    int num1 = 10, num2 = 20;
    
    // Catching the returned value
    int result = addNumbers(num1, num2);

    cout << "The sum is: " << result << endl;
    
    // Direct usage
    cout << "Direct sum: " << addNumbers(50, 50) << endl;

    return 0;
}

⚠️ Scope Alert!

I learned an important concept: Local Scope. Variables created inside a function (like sum above) cannot be accessed inside main(). They die when the function ends.

💭 Thoughts

Functions are powerful. Next up, I need to understand Pass by Value vs Pass by Reference because I heard that changes variables differently.