Question

Write the definition of a void function that takes as input a decimal number and as output 3 times the value of the decimal number. Format your output to two decimal places.

Short answer

Write a void function to multiply the input by 3 and print it formatted to two decimal places.

Step-by-step solution

Understand the Problem

We need to write a void function that takes a decimal number as input and outputs three times that number, formatted to two decimal places. A void function in programming does not return a value but may print or modify data.

Determine the Function Signature

Since this is a void function, it only needs to take a single input parameter - a decimal number. This implies our function should have a signature like `void function_name(decimal_input)`.

Implement Input Multiplier

The function needs to calculate three times the decimal input. This involves multiplying the input by 3. If the input is `x`, then we compute `3 * x`.

Format the Output

The problem requires the output to be formatted to two decimal places. We can achieve this in many programming languages using formatting tools like `printf`, `format`, or similar depending on the language in use.

Print the Result

Finally, the function should print the formatted result. The result should be like `print_formatted(3 * x)`, where the actual printing command will depend on how formatting is handled in the specific programming language.

Write the Full Function

Write out the full function combining all steps above. For example, in Python: ```python def multiply_and_print(decimal_number): result = 3 * decimal_number print(f"{result:.2f}") ``` This script multiplies the input by 3, formats it to two decimal places, and prints the result.

Key concepts

Void Function

A 'void function' is a fundamental concept in C++ programming and many other languages. It is defined as a type of function that does not return a value. Instead of providing a result back to the part of the program that called it, a void function may perform its tasks such as outputting data or altering objects.
This is useful when the main purpose of the function is to execute an action rather than compute and return a value. For example, consider a function that prints a message to the screen. Since the main objective is simply to display information, returning a value is unnecessary. A void function thus allows a programmer to encapsulate the steps to perform the desired action without concerning itself with outputting a value that other parts of the program might need to handle.

• Void functions can take parameters, allowing them to work on input data.
• They do not have a return type. In C++, this is explicitly indicated by the keyword 'void'.
• These functions are suitable for operations where the side effect like printing to console, logging, or modifying a passed reference is the goal.

Decimal Number

In programming, working with decimal numbers often involves understanding and accurately handling floating-point numbers. These are numbers that can have a fractional component, as opposed to whole numbers (integers).
Decimal numbers are crucial in fields such as financial calculations, scientific computing, and any domain where precision is important.
In C++, the standard types used to store decimal numbers and allow for fractional amounts are typically `float`, `double`, and `long double`. These data types vary in precision:

• `float` is usually 4 bytes, with a precision of up to 7 decimal digits.
• `double` is typically 8 bytes, providing precision up to about 15 decimal digits.
• `long double` can offer even more precision if supported by the system.

Understanding how to handle these data types properly, including operations like addition, multiplication, and division, is key to maintaining precision and accuracy in numerical computations.

Output Formatting

Output formatting is an essential part of programming when presenting data. In C++ and many other programming languages, correctly formatting output is crucial for ensuring data is readable and meets requirements such as specific decimal places.
Employing appropriate formatting methods enhances the clarity and precision of the outputs, especially when dealing with decimal numbers. For instance, when displaying a result like 7.123456, formatting it to two decimal places would render it 7.12, which is more readable and often necessary for precision tasks.
In C++, you can use functions from the I/O stream library to format output:

• std::cout.precision(2) to set the number of significant digits, followed by std::fixed if you want to ensure the decimal places are maintained.
• std::setw() for setting width, std::setprecision() aligning numbers, etc.
• Libraries like iomanip provide additional tools for finer control over the output display.

By using these tools, programmers can ensure that the outputs meet specifications for business reports, scientific research, etc.

Function Signature

A function signature is an important concept in programming as it defines the interface for a function. It typically includes the function name, the return type, and the parameters it takes. In C++, a function signature can help in identifying a function uniquely within a program based on the provided parameter list and the return type.
When designing a function in C++, especially a void function, the signature would exclude a return type value but include any parameters that the function requires to perform its task. For example, void multiply_and_print(double decimal_number) is a valid function signature, where:

• void indicates that the function does not return any value.
• multiply_and_print is the name of the function, providing insight into the function's purpose.
• double decimal_number is a parameter that specifies the input the function will process.
• This parameter list (the input types and names) distinguishes one function from another, especially in overloaded functions where the names are the same but parameters differ.

Understanding function signatures helps in reading and writing code as they act as a contract, detailing what information a function can handle and what behavior it holds.