Question

Write a function named getNumber that uses a reference parameter variable to accept an integer argument. The function should prompt the user to enter a number in the range of 1 through 100. The input should be validated and stored in the parameter variable.

Short answer

Question: Write a C++ function called `getNumber` that accepts a reference parameter variable to store an integer, prompts the user to enter a number between 1 and 100, and validates the input. Answer: To write the `getNumber` function, you should follow these steps: 1. Include the necessary headers and declare the `getNumber` function. 2. Define the function that prompts the user to enter a number and validates the input. 3. Write a `main` function to test the `getNumber` function. Here's a sample implementation: ```cpp #include #include void getNumber(int &number); int main() { int userNumber; getNumber(userNumber); std::cout << "You entered: " << userNumber << std::endl; return 0; } void getNumber(int &number) { while (true) { std::cout << "Please enter a number between 1 and 100: "; std::cin >> number; if (number >= 1 && number <= 100) { break; } else { std::cerr << "Invalid input. Try again." << std::endl; std::cin.clear(); std::cin.ignore(std::numeric_limits::max(), '\n'); } } } ```

Step-by-step solution

Include required headers and declare the function

To start, we need to include the necessary headers and declare the `getNumber` function. Include the "" header for input and output and the "" header to obtain the maximum and minimum value of integers. ```cpp #include #include void getNumber(int &number); ```

Define the getNumber function

Now let's write the `getNumber` function. We'll need to prompt the user to enter a number between 1 and 100 and then validate the input. ```cpp void getNumber(int &number) { while (true) { std::cout << "Please enter a number between 1 and 100: "; std::cin >> number; if (number >= 1 && number <= 100) { break; } else { std::cerr << "Invalid input. Try again." << std::endl; std::cin.clear(); std::cin.ignore(std::numeric_limits::max(), '\n'); } } } ```

Test the getNumber function

Finally, let's write a `main` function to test the `getNumber` function. ```cpp int main() { int userNumber; getNumber(userNumber); std::cout << "You entered: " << userNumber << std::endl; return 0; } ``` Now the student should have a clear idea of how to write a function that uses a reference parameter and validates the input.

Key concepts

Input Validation in C++

Validating user input is a critical aspect of robust programming. In C++, input validation ensures that the data provided by a user meets certain criteria before it is processed further. For example, when asking for a number within a specific range—as seen in the getNumber function—the program needs to verify that the number entered by the user falls between 1 and 100.

Using a combination of control structures like if statements and loops is a common input validation strategy. In the provided solution, the validation takes place inside a while loop that continuously prompts the user for input until the condition is met. If the user enters an invalid value, the program provides feedback and prompts them again.

To help with input validation, C++ provides functions such as cin.fail() to detect input failures and cin.clear() to reset the input stream to a usable state. The cin.ignore() function is used to clear the input buffer, preventing any remaining unwanted input from affecting subsequent reads.

Writing Functions in C++

Functions in C++ are modular blocks of code that perform a specific task. Writing a function involves declaring its return type, name, and parameters. In the exercise, the function getNumber is defined to accept a reference parameter, indicated by the ampersand (&), meaning that any change to the parameter variable within the function will reflect in the argument passed.

Reference parameters are useful when you need to modify the passed arguments and reflect the changes outside the function. Let's explore the function-writing process in the context of the getNumber function:

Declaration

• The function is first declared at the start of the program to inform the compiler about its existence.

Definition

• The function's body contains the logic to execute its task. It's where input validation takes place in our scenario.

Calling the Function

• The function is then called from the main function, or another function, and the actual value that needs to be processed is passed as an argument.

Using functions can greatly simplify your code by breaking down complex operations into smaller, more manageable pieces.

C++ While Loops

The while loop in C++ is a control flow statement that allows code to be executed repeatedly based on a given Boolean condition. The code inside the loop will continue to run as long as the condition is true. Here's a basic structure of a while loop:

while (condition) {
// Code to be executed
}
In the context of our getNumber function example, the while loop is used for input validation. It helps in creating a prompt-retry loop where the user is constantly asked for input until the correct input is provided. This is especially useful in situations where we cannot predict how many times the user might enter invalid input.

Since the loop can potentially run indefinitely, it's important to manage loops carefully to avoid infinite loops which can lock up your program. In the solution provided, the loop is safely exited using a break statement when valid input is received, ensuring the program continues only with appropriate data.

C++ Input Output

Standard input and output operations in C++ are handled through the iostream library, which includes objects such as cin for input and cout for output. The header is essential for any program that requires user interaction via the terminal.

To receive data from the user, cin is used in conjunction with the extraction operator (>>). The user's input is then stored in a variable. Outputting information back to the user is done with cout and the insertion operator (<<).

In the getNumber function, the validated user input is displayed back to the user using cout. When the input fails validation, the error message is displayed using cerr, which is similar to cout but is used for error messages, making the output more suitable for debugging purposes. Learning to effectively manage input and output is critical for creating user-friendly applications that communicate clearly and effectively with their users.