C++ - Parameters and Arguments

Parameters and Arguments in C++ 

Introduction

In C++, functions can take inputs in the form of parameters, and when calling a function, you pass values to those parameters. These values passed to the function are known as arguments. Understanding parameters and arguments is crucial for working with functions in C++.

Parameters

Parameters are the variables defined in the function declaration or definition. They act as placeholders for the values that will be passed into the function when it is called.

Types of Parameters

• Formal Parameters: These are the parameters listed in the function declaration or definition. They are placeholders used to define what type of data the function will accept.
• Actual Parameters: These are the variables or values passed to the function when it is called.

Syntax for Defining Parameters

return_type function_name(parameter1, parameter2, ...) {
    // Function body
}
    

Example

#include 
using namespace std;

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

int main() {
    greet("Alice"); // "Alice" is the argument passed to the parameter "name"
    return 0;
}
    

Output

Hello, Alice!
    

Arguments

Arguments are the actual values or expressions passed to the function when it is called. These values are assigned to the corresponding parameters in the function.

Types of Arguments

• Actual Arguments (or Real Arguments): The actual values or variables passed to the function when calling it.
• Default Arguments: These are values that the function can assume if no argument is passed during the function call. Default arguments are provided in the function declaration.

Syntax for Passing Arguments

function_name(argument1, argument2, ...);
    

Example with Default Arguments

#include 
using namespace std;

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

int main() {
    greet("Alice");   // Argument passed is "Alice"
    greet();          // No argument passed, "Guest" is used as the default
    return 0;
}
    

Output

Hello, Alice!
Hello, Guest!
    

Types of Argument Passing

In C++, there are two main ways to pass arguments to functions: by value and by reference.

1. Pass by Value

When you pass an argument by value, a copy of the actual value is passed to the function. Changes made to the parameter inside the function do not affect the actual argument.

Example of Pass by Value

#include 
using namespace std;

void modifyValue(int num) {
    num = num * 2; // This change will not affect the original argument
}

int main() {
    int x = 5;
    modifyValue(x);
    cout << "x after function call: " << x << endl; // x remains unchanged
    return 0;
}
    

Output

x after function call: 5
    

2. Pass by Reference

When you pass an argument by reference, the function works directly with the original variable. Changes made to the parameter will affect the original argument.

Example of Pass by Reference

#include 
using namespace std;

void modifyValue(int &num) {
    num = num * 2; // This will change the original argument
}

int main() {
    int x = 5;
    modifyValue(x);
    cout << "x after function call: " << x << endl; // x will be modified
    return 0;
}
    

Output

x after function call: 10
    

Advantages of Parameters and Arguments

• They allow functions to work with dynamic data, making the code reusable and flexible.
• By passing arguments, you can make functions operate on different values each time they are called.
• They enable the use of default values, simplifying function calls when certain values are not necessary.

Parameters and arguments are fundamental concepts in C++ that allow functions to be more flexible and reusable. Understanding how to use them effectively is essential for writing efficient and maintainable code.