Functions in C++ allow you to encapsulate a block of code that performs a specific task or a set of instructions. Functions provide modularity, reusability, and improved code organization. In C++, you can define functions to perform operations, manipulate data, and return values. Functions can also accept parameters as inputs and modify them using pass-by-value or pass-by-reference semantics.

Here's an example that demonstrates the usage of functions in C++:

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#include <iostream> // Function declaration or prototype int addNumbers(int a, int b); // Function definition int addNumbers(int a, int b) {    int sum = a + b;    return sum; } int main() {    int num1 = 5;    int num2 = 10;    // Function call    int result = addNumbers(num1, num2);    std::cout << "The sum is: " << result << std::endl;    return 0; }

In this example, we declare a function addNumbers that takes two integers (a and b) as parameters and returns an integer. The function definition specifies the implementation of the function by calculating the sum of a and b and returning the result.

In the main function, we declare two integer variables num1 and num2 and assign them values. We then call the addNumbers function, passing num1 and num2 as arguments. The return value of the function is stored in the result variable.

Finally, we print the result using std::cout.

You can create your own functions to perform specific operations based on your requirements. Functions can have different return types (void for no return, or any other data type), and they can have different parameter types and quantities.

Additionally, functions can be defined before or after their usage through function prototypes or declarations. Function prototypes specify the function signature (return type, name, and parameter types) without the actual implementation. This allows you to use a function before defining it.

Feel free to modify and expand this code to practice different functions, function parameter passing, and return types.