C++ Parameters

Function Parameters in C++

In C++, parameters are used to pass information into functions. Think of them as the inputs that functions use to perform their tasks. When you call a function, you can pass values (called arguments), and those values are caught by the parameters in the function definition.

Basic Parameter Example

Let’s create a function that takes two parameters and prints their sum:

#include <iostream>
using namespace std;

void printSum(int a, int b) {
    cout << "Sum is: " << (a + b) << endl;
}

int main() {
    printSum(10, 20);  // Passing arguments
    return 0;
}
  

Call by Value

When you pass arguments by value, the function gets a copy of the variables. Changes made inside the function do not affect the original variables.

#include <iostream>
using namespace std;

void changeValue(int x) {
    x = 100;
}

int main() {
    int num = 50;
    changeValue(num);
    cout << "Original num: " << num << endl;
    return 0;
}
  

Call by Reference

With reference parameters, the function receives the actual variables. Changes made inside the function affect the original values.

#include <iostream>
using namespace std;

void changeValue(int &x) {
    x = 100;
}

int main() {
    int num = 50;
    changeValue(num);
    cout << "Changed num: " << num << endl;
    return 0;
}
  

Default Parameters

You can also give default values to parameters. If no argument is passed, the default is used!

#include <iostream>
using namespace std;

void greet(string name = "Guest") {
    cout << "Hello, " << name << "!" << endl;
}

int main() {
    greet();            // Uses default
    greet("Charlie");   // Uses provided value
    return 0;
}
  

Summary

• Parameters are variables listed in a function’s definition.
• You pass arguments when you call the function.
• Call by value: function works with a copy.
• Call by reference: function works with the actual variable.
• Default parameters provide fallback values.

Mastering parameters makes your functions powerful and flexible.