Question

Write a complete \(C++\) program that asks the user for a number of gallons and then outputs the equivalent number of liters. There are 3.78533 liters in a gallon. Use a declared constant. since this is just an exercise, you need not have any comments in your program.

Short answer

Question: Write a C++ program that converts a given amount of gallons to liters using the conversion factor 1 gallon = 3.78533 liters. Answer: ```cpp #include #include const double GALLON_TO_LITER = 3.78533; int main() { double gallons, liters; std::cout << "Enter the amount in gallons: "; std::cin >> gallons; liters = gallons * GALLON_TO_LITER; std::cout << std::fixed << std::setprecision(2) << gallons << " gallons is equal to " << liters << " liters." << std::endl; return 0; } ```

Step-by-step solution

(Step 1: Include necessary libraries)

Include the `iostream` library for input-output operations, and 'iomanip' library for output formatting. ```cpp #include #include ```

(Step 2: Declare constant)

Declare the conversion factor between gallons and liters as a constant. ```cpp const double GALLON_TO_LITER = 3.78533; ```

(Step 3: Initialize variables)

Initialize the variables for holding user input and the converted value. ```cpp double gallons, liters; ```

(Step 4: Input validation loop)

This step is optional. For this example, we will skip the input validation loop.

(Step 5: Input-output and calculation)

Receive user input, convert the gallons to liters using the conversion factor, and display the result. ```cpp int main() { std::cout << "Enter the amount in gallons: "; std::cin >> gallons; liters = gallons * GALLON_TO_LITER; std::cout << std::fixed << std::setprecision(2) << gallons << " gallons is equal to " << liters << " liters." << std::endl; return 0; } ``` Final C++ program: ```cpp #include #include const double GALLON_TO_LITER = 3.78533; int main() { double gallons, liters; std::cout << "Enter the amount in gallons: "; std::cin >> gallons; liters = gallons * GALLON_TO_LITER; std::cout << std::fixed << std::setprecision(2) << gallons << " gallons is equal to " << liters << " liters." << std::endl; return 0; } ```

Key concepts

Gallon to liter conversion

Converting gallons to liters is a fundamental operation in various disciplines, including science and engineering.
One gallon is equivalent to 3.78533 liters. To perform the conversion, you would multiply the number of gallons by this conversion factor. This operation is often encountered in exercises that involve unit conversion and provides a practical example of real-world mathematical application.

Practical Usage

In the given programming exercise, the user is asked for a quantity in gallons, which the program then converts into liters using this conversion factor. By understanding such conversions, students can apply these concepts to solve practical problems that involve liquid volumes in different measurement systems.

C++ constants declaration

In C++, declaring constants is a way of assigning a meaningful name to a value that does not change throughout the execution of the program. This practice aids in code maintainability and readability.

Benefits of Using Constants

• Prevents accidental modification of values that should remain constant.
• Makes the code more readable and understandable.
• Eases the process of making changes to the value, as it's defined only once.

Using the 'const' keyword, you can declare a constant as shown in the code snippet provided in the solution. In this exercise, the conversion factor between gallons and liters is declared as a constant, reinforcing good programming practices.

Including libraries in C++

Libraries in C++ are collections of pre-compiled code that can be used to add functionality to programs. To use the functionality that a library provides, it must be included at the beginning of the C++ program file.
For example, including iostream enables the program to perform input and output operations such as reading from the keyboard and printing to the console.

Common C++ Libraries

• iostream: Standard input-output stream
• iomanip: Input-output manipulators for formatting
• vector: Part of the Standard Template Library for using dynamic arrays

In the provided exercise, the iostream library is used for input and output operations, whereas the iomanip is used for setting precision when outputting the liters.

Input and output in C++

Input and output (I/O) operations are fundamental in C++ programs, providing a way for users to interact with the program. The 'cin' and 'cout' objects, which are part of the iostream library, handle standard input and standard output, respectively.
To read input from the user, the 'std::cin' object is used, and to display messages or results, the 'std::cout' object is utilized. Additionally, proper formatting can be achieved using manipulators such as 'std::fixed' and 'std::setprecision', which you can notice in the given solution.

Format Control with I/O

These manipulators make the output user-friendly and easier to understand, essential in building professional and functional programs. For instance, setting the precision dictates how many digits appear after the decimal point in floating-point numbers. In our exercise, these I/O operations and formatting techniques provide a clear, concise display of the conversion results.