Question

Write a cout statement so the variable totalAge is displayed in a field of 12 spaces, in fixed point notation, with a precision of 4 decimal places.

Short answer

Question: Write a C++ statement that displays a variable called `totalAge` with the following format: occupying 12 spaces, using fixed-point notation, and displaying 4 decimal places. Answer: `cout << fixed << setprecision(4) << setw(12) << totalAge << endl;`

Step-by-step solution

Include necessary header file and namespace

To use `cout` statement, include the `iostream` header file and use the `std` namespace: ```cpp #include using namespace std; ```

Set fixed point notation

Set the output format to fixed point notation by using `fixed` standard manipulator: ```cpp cout << fixed; ```

Set precision

Set the precision to 4 decimal places using `setprecision` from the `iomanip` header file: ```cpp #include cout << setprecision(4); ```

Set field width

Set the field width to 12 spaces using `setw` from the `iomanip` header file: ```cpp #include cout << setw(12); ```

Display totalAge variable

Finally, use the `cout` statement to display the `totalAge` variable with the specified format: ```cpp cout << totalAge << endl; ```

Complete Solution

Here's the complete solution for the given task: ```cpp #include #include using namespace std; int main() { double totalAge = 25.1234; cout << fixed << setprecision(4) << setw(12) << totalAge << endl; return 0; } ```

Key concepts

iostream library

In C++, the iostream library is a fundamental component since it provides functionalities for input/output operations. The term 'iostream' is actually shorthand for 'input-output stream'. Streams are an abstraction that allows us to send data to and receive data from different sources, typically the console, files, strings, or more intricate data sources like network sockets. The library includes essential objects such as cin for input and cout for output.

When you're writing code that should display information to a user or receive input from a keyboard, the iostream library is what makes this possible. For instance, cout, which stands for 'console output', is used to print text and variables to the console. To utilize the iostream library properly, it's a common practice to include its header at the beginning of your C++ programs with #include <iostream> and to use the namespace std, which is where all the standard library components, including those from iostream, are defined.

iomanip library

While the iostream library provides you with the basic tools for input and output in C++, the iomanip library steps in to offer more control over how the data is actually formatted. This library includes I/O manipulators that allow us to alter the presentation of the data without changing the data itself. For fine-tuning output, #include <iomanip> is inserted at the beginning of the code, similar to other libraries in C++.

The problem you're tackling is a perfect example of why the iomanip library is useful: you're asked to display a variable in fixed point notation with a specific field width and precision. Commands such as setprecision() and setw() are part of this library and are crucial for this task. setprecision() allows you to define how many digits after the decimal point should be displayed, while setw() sets the width of the next output field, ensuring that your numbers line up visually in columns and are easy to read.

cout formatting

Formatting your output can make a world of difference when it comes to readability and presentation of data. The cout statement, used alongside various formatting tools, is what allows for such customization in C++. The exercise demonstrates how to apply complex formatting to a variable being printed to the console. By chaining manipulators like fixed and setprecision(), one after another in a cout statement, you can control not just the precision and field width, but also the notation of the number.

fixed is a manipulator ensuring that the number is output using fixed point notation (as opposed to scientific notation) which means it always shows a number exactly as it is, with the specified number of decimal places. It’s particularly useful when you’re dealing with monetary values or other precise measurements. It transforms how cout displays floating-point numbers so that they're shown in a familiar decimal format regardless of their value. These formatting tools derive their power from the fact that they are stateful; once set, they affect all subsequent output operations until they are changed again or the program ends. Remember, when using these manipulations, they should come directly before the variable or value to be formatted, just as shown in the step-by-step solution of the exercise.