Question

Write a cout statement so the variable population is displayed in a field of 12 spaces, left-justified, with a precision of 8 decimal places. The decimal point should always be displayed.

Short answer

Answer: The manipulators to use are setw(12), left, setprecision(8), and showpoint.

Step-by-step solution

Set field width

Set the field width to 12 spaces using the setw manipulator from the iostream library. This is done by including the library and using setw(12) with the cout statement.

Set precision

Set the precision to 8 decimal places using the setprecision manipulator from the iostream library. This is done by including the library and using setprecision(8) with the cout statement.

Set left-justification

Set the left-justification using the left manipulator from the iostream library. This is done by including the library and using the left manipulator with the cout statement.

Force the display of the decimal point

Force the display of the decimal point using the showpoint manipulator from the iostream library. This is done by including the library and using the showpoint manipulator with the cout statement.

Write the cout statement

Combine the manipulators with the population variable in the cout statement to display it in the desired format. Here is the final cout statement: ```cpp #include #include int main() { double population = 1234567.89101112; std::cout << std::setw(12) << std::left << std::setprecision(8) << std::showpoint << population << std::endl; return 0; } ```

Key concepts

setw manipulator

In C++, the `setw` manipulator is a tool for adjusting the field width when displaying an output. Imagine it as setting the width of a box where your output will be placed. For example, if you use `std::setw(12)`, it means you want the output to take up 12 spaces.

• This can be extremely helpful if you need your output neatly aligned, which is often needed in tables or reports.
• Keep in mind that `setw` only affects the next item that is sent to the output stream, so it must be repeated for each different output.

Importantly, remember to include the `iomanip` header (`#include `) to access `setw` and other manipulators.

setprecision manipulator

The `setprecision` manipulator in C++ is used to specify the number of digits to be displayed after the decimal point for floating-point numbers. It can also affect the total number of significant digits shown depending on how the output is formatted.

• When combined with the `fixed` manipulator, `setprecision(n)` ensures that `n` decimal places are shown.
• This is particularly useful for displaying monetary values, scientific measurements, or any data that requires a specific degree of accuracy.

It's crucial to ensure the `iomanip` library is included to make use of this function effectively: `#include `.

left-justification

By default, output in C++ is right-aligned, meaning it's pushed to the right side of the field. To change this, the `left` manipulator is used, allowing text and numbers to start from the left-hand side of a defined field width.

• When you use `std::left`, everything that follows will be aligned to the left edge of any defined width.
• For it to work well, you should often use it in conjunction with `setw` to define that width, providing a neat structure to your output.

Alignment is critical in creating readable output, especially when dealing with columns of data or formatted reports.

showpoint manipulator

The `showpoint` manipulator is employed to ensure that the decimal point is always displayed, even when numbers are whole. This can be particularly useful for financial data, where consistent formatting is key.

• For instance, if you use `std::showpoint` with `double number = 45;`, it will display as `45.0` when printed, providing clarity in cases where decimal precision is implied but not shown.
• Using `showpoint` prevents any ambiguity that could arise from omitting decimal points.

This manipulator is straightforward to use but has a significant impact on the readability and clarity of numerical data in C++ outputs.