Passing Arguments to Functions (Pass by Value, Pass by Reference)

In C++ programming language, passing arguments to functions allows us to provide input values that can be manipulated or used within the function body. There are two ways to pass arguments to functions: pass by value and pass by reference. Let's explore each of them in detail.

Pass by Value

By default, when you pass arguments to a function in C++, they are passed by value. This means that a copy of the argument is created within the function scope and any changes made to the parameter inside the function do not affect the original argument.

Syntax: cpp return_type function_name(data_type parameter_name);

Here's an example demonstrating pass by value:

#include <iostream>

void square(int num) {
    num = num * num; // Manipulate the parameter
    std::cout << "Inside the function: " << num << std::endl;
}

int main() {
    int number = 5;
    square(number); // Call the function
    std::cout << "Outside the function: " << number << std::endl;
    return 0;
}

Output: Inside the function: 25 Outside the function: 5

As you can see, the square() function receives a copy of the number parameter. It manipulates the value inside the function to calculate the square, but the original number remains unchanged.

Pass by Reference

Passing arguments by reference allows us to pass the memory address of the argument to the function. This means any changes made to the parameter inside the function will affect the original argument.

Syntax: cpp void function_name(data_type& parameter_name);

Here's an example demonstrating pass by reference:

#include <iostream>

void square(int& num) {
    num = num * num; // Manipulate the parameter by reference
    std::cout << "Inside the function: " << num << std::endl;
}

int main() {
    int number = 5;
    square(number); // Call the function
    std::cout << "Outside the function: " << number << std::endl;
    return 0;
}

Output: Inside the function: 25 Outside the function: 25

In this case, the square() function receives the memory address of the number parameter. Therefore, any changes made to num inside the function directly affect the original number.

Benefits of Pass by Reference

Passing arguments by reference can be useful in the following scenarios:

• Efficient memory utilization since no additional memory is allocated for the copy of the argument.
• Ability to modify the original argument, making it useful for functions with return values.

When to Use Which Method?

• Use pass by value when you don't want the called function to modify the original value of the argument.
• Use pass by reference when you want the called function to modify the original value of the argument or when the argument is large and passing by value would result in performance issues.

Both passing methods have their own advantages and should be used accordingly, depending on the specific requirements of your program.

In conclusion, understanding the differences between passing arguments by value and by reference is crucial in C++ programming. Knowing when to use each method can help you write efficient and maintainable code.