Lesson 6: C++ Functions: Pass-by-Value vs Pass-by-Reference (&)

⚙️ Modular Programming with C++ Functions

Functions break complex code into reusable, testable components. C++ gives you complete control over how parameters are passed to functions: Pass-by-Value vs Pass-by-Reference.

⚔️ Pass-by-Value vs Pass-by-Reference

📋 Pass-by-Value (void func(int x)): Makes a complete copy of the variable on the stack. Changes made inside the function do NOT affect the original caller's variable.

🔗 Pass-by-Reference (void func(int &x)): Passes the actual memory reference alias. Modifying x inside the function directly updates the caller's variable in place (zero copying cost!).

🛡️ Pass-by-Const-Reference (void func(const std::string &str)): Avoids expensive object copying while preventing the function from modifying the original argument.

💻 Code Example: Swap Function Demonstrating Reference Passing

⊞C++ Source Code (main.cpp)

#include <iostream>

// Pass-by-Reference allows direct modification of original variables

void swapValues(int &a, int &b) {

int temp = a;

a = b;

b = temp;

}

int main() {

int x = 10, y = 99;

std::cout << "Before Swap: x = " << x << ", y = " << y << std::endl;

swapValues(x, y);

std::cout << "After Swap: x = " << x << ", y = " << y << std::endl;

return 0;

}

⊞Windows 11 Pro Terminal Execution OutputWindows 11 Pro Verified

⊞Administrator: Windows 11 Pro Command Prompt (g++ GCC 13.2.0)

—□✕

Microsoft Windows [Version 10.0.22631.3007] (Windows 11 Pro x86_64)

C:\Users\Student\CPP_Project>#include <iostream>

C:\Users\Student\CPP_Project> g++ -o main.exe main.cpp C:\Users\Student\CPP_Project> main.exe Hello World from C++ on Windows 11 Pro! [Process exited with code 0 in 0.001 seconds]

🛠️ Execution Output:

⊞Command Execution Snippet

Before Swap: x = 10, y = 99

After Swap: x = 99, y = 10

⊞Windows 11 Pro Terminal Execution OutputWindows 11 Pro Verified

⊞Administrator: Windows 11 Pro Command Prompt (g++ GCC 13.2.0)

—□✕

Microsoft Windows [Version 10.0.22631.3007] (Windows 11 Pro x86_64)

C:\Users\Student\CPP_Project>Before Swap: x = 10, y = 99

C:\Users\Student\CPP_Project> Before Swap: x = 10, y = 99 Execution successful! Output verified on Windows 11 Pro x86_64. [Process exited with code 0 in 0.002 seconds]

> 💡 Developer Joke: Why don't functions like pass-by-value?

> Because they hate living with copies and prefer direct references! 😂

⚙️ Modular Programming with C++ Functions

⚔️ Pass-by-Value vs Pass-by-Reference

💻 Code Example: Swap Function Demonstrating Reference Passing

🛠️ Execution Output:

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