Question

A mail order house sells five different products whose retail prices are: product \(1 \$ 2.98,\) product \(2 \$ 4.50,\) product \(3 \$ 9.98,\) product \(4 \$ 4.49\) and product \(5 \$ 6.87 .\) Write a program that reads a series of pairs of numbers as follows: a. product number b. quantity sold Your program should use a switch statement to determine the retail price for each product. Your program should calculate and display the total retail value of all products sold. Use a sentinel-controlled loop to determine when the program should stop looping and display the final results.

Short answer

Use a loop with a switch statement to calculate and sum product sales, ending with a sentinel value.

Step-by-step solution

Understand the Problem

We need to write a program that reads a series of product numbers and quantities sold, calculates the total retail value of the products sold, and uses a sentinel value to end input collection and print the final results.

Define Product Prices and Inputs

Define the prices for each product: product 1 is $2.98, product 2 is $4.50, product 3 is $9.98, product 4 is $4.49, and product 5 is $6.87. Define how the program should accept inputs for product number and quantity, taking into account the sentinel value for loop termination.

Implement the Input Loop with Sentinel

Create a loop to continually read product number and quantity pairs. Use a sentinel-controlled loop by accepting a special value (e.g., 0 for the product number) to indicate when the program should stop collecting input.

Use a Switch Statement for Price Calculation

Within the loop, use a switch statement to determine the price of each product based on its number. Multiply the quantity by the price to get the total for each transaction and keep a running total of all sales.

Display the Total Retail Value

Once the input loop ends (when the sentinel value is encountered), display the total retail value of all products sold that was accumulated during the loop.

Key concepts

switch statement

In C++ programming, the `switch` statement is a control structure that makes decisions based on the value of a single variable or expression. It is similar to a series of `if-else` statements but provides a more efficient way to handle a variable with many possible values.

The `switch` statement begins with the keyword `switch`, followed by the variable being evaluated inside parentheses. This is then followed by a series of `case` statements which represent the possible values of the variable. Each `case` is followed by a block of code executed when the variable matches the case's value.

A typical structure of a `switch` statement looks like this:

• `switch(expression) {`
• ` case constant1: // code to execute; break;`
• ` case constant2: // code to execute; break;`
• ` // more cases as needed`
• ` default: // code to execute if none of the cases match`
• `}`

In scenarios like this exercise, where each product number corresponds to a unique price, using a `switch` statement ensures that the correct price gets identified quickly. When a case in the `switch` statement is matched, its corresponding code is executed, and control is transferred out of the `switch` block using the `break` statement. If none of the cases match, the `default` block can handle unexpected input.

sentinel-controlled loop

A `sentinel-controlled loop` is a common technique in C++ programming for repeatedly executing a block of code until a specific condition is met. This condition is often the detection of a 'sentinel' value, a special value that signifies the end of data input.

In the context of our exercise, the loop continues to prompt the user for product numbers and quantities until they enter a sentinel value, such as `0` for 'product number', that signifies the end of the input stream. This technique is particularly useful in situations where the number of iterations is not known beforehand.

The basic structure of a sentinel-controlled loop can look like this:

• `int productNumber;`
• `cin >> productNumber;`
• `while (productNumber != sentinelValue) {`
• ` // process input`
• ` cin >> productNumber;`
• `}`

Using this method, input handling becomes dynamic. As long as users avoid entering the sentinel, the loop continues to prompt for inputs. Only when the sentinel is detected does the loop stop, making this an elegant solution for situations involving unpredictable input lengths.

input handling in C++

Input handling in C++ is essential for creating interactive programs that can dynamically respond to user input. C++ uses streams to facilitate input and output operations, with `cin` managing input from the keyboard. This is particularly important in our exercise, where we need to gather product numbers and quantities from the user.

The `cin` object is associated with the standard input, usually the keyboard, allowing the program to read user input easily. For example:

• `int productNumber;`
• `int quantity;`
• `cin >> productNumber >> quantity;`

In this snippet, the program reads two integers, one for the product number and another for the quantity, directly from user input.

To ensure robust input handling, you might also consider additional error checks to handle unexpected input types, like entering a letter when a number is needed. Methods like `cin.clear()` to clear error flags and `cin.ignore()` to skip unwanted input can be beneficial in such cases.

Input validation can further enhance the program's resilience, ensuring that only valid data, such as non-negative product numbers and quantities, are processed.

retail price calculation

Calculating retail prices is crucial in programs dealing with sales and commerce as in our exercise. The basic idea is to determine the total sale amount based on the quantity of each product sold and its retail price.

For each transaction, the steps typically include:

• Identify the product number.
• Use a `switch` statement to retrieve the corresponding product price.
• Multiply the product price by the quantity sold to calculate the transaction total.

This calculated total is then added to a running sum, which represents the cumulative total of all transactions processed. Here’s a simplified view of how you might compute it repeatedly:

• `double totalSales = 0.0;`
• `totalSales += productPrice * quantity;`

Continuing this process throughout the loop accumulates the total sales value. Once all products have been processed and the sentinel condition is met, the complete sales figure is displayed.

By automating the retail price calculation, businesses can perform sales analysis efficiently, ensuring accuracy and saving valuable resources.