Question

Write code that lets the user enter a number. The number should be multiplied by 2 and printed until the number exceeds \(50 .\) Use a while loop.

Short answer

Question: Write a Python code that takes a number from the user and multiplies it by 2 repeatedly using a while loop until the number becomes greater than 50. Show the current value of the number each time it is multiplied.

Step-by-step solution

Get User Input

To start, we need to get a number from the user. This can be done using the input() function. Since input() returns a string, it needs to be converted to a numeric type like an integer (int) for this exercise.

Create a While Loop

Next, we need to create a while loop with a condition such that it continues to run until the input number exceeds 50. We will check if the number is less than or equal to 50, and if it is, we will continue with the loop.

Multiply the Number by 2

Inside the while loop, multiply the number by 2, and overwrite the current value of the number with the new value. It will keep on multiplying until the number becomes greater than 50.

Print the Result

After multiplying the number by 2, print the result to show the current value of the number each time it is multiplied. Here is a complete code to solve this exercise: ```python # Step 1: Get user input number = int(input("Enter a number: ")) # Step 2: Create a while loop while number <= 50: # Step 3: Multiply the number by 2 number = number * 2 # Step 4: Print the result print(number) ```

Key concepts

Control Structures

Control structures in programming allow us to direct the flow of the program based on conditions or the occurrence of events. The most basic control structures are conditional statements like if, else, and loops such as while and for. In the context of our C++ exercise, we utilize a while loop, which is a control structure that repeats a section of code as long as its condition evaluates to true.

In this case, the loop continues to execute multiplying the input number by 2 and printing the output until the result exceeds 50. This use of a while loop demonstrates a typical scenario where we need to perform an action repetitively until a certain condition is met, showcasing the importance and utility of control structures in programming.

User Input Handling

Handling user input is crucial in interactive programs. It allows for dynamic behavior of the application based on the user's actions. In many programming languages including C++, obtaining user input is frequently done using built-in functions or methods. Although the provided example is in Python, in C++ we often use cin to capture input from the standard input device, typically the keyboard.

To effectively manage user input, one must ensure that the input is of the correct type and is valid for the operation it is intended for. For instance, if a program expects an integer but the user provides a string, this could lead to runtime errors or undefined behavior. Therefore, validating and possibly converting user input, as in converting a string to an integer using stoi or similar functions, is a vital part of user input handling.

Loop Condition

The loop condition is the heart of a loop control structure, determining its longevity or repetition frequency. It is evaluated before each iteration, and as long as it is true, the loop continues. In the exercise, the condition is number <= 50.

This condition ensures that our loop does not run indefinitely and has a clear termination point—when the number exceeds 50. Creating an effective loop condition requires understanding the problem's requirements and ensuring the loop fulfills its purpose without causing infinite loops or premature termination. Good loop conditions are succinct and directly related to the loop's goal.

Integer Multiplication

Integer multiplication is one of the basic arithmetic operations performed in almost all programming languages. It takes two integers and produces a new integer that is their product. In a programming context, especially when dealing with loops, integer multiplication can be used to create multiples or to scale values.

In our exercise, we multiply the user's input number by 2 within each loop iteration, doubling it repeatedly. The syntax for multiplication in C++ is the asterisk (*), and the operation has precedence rules which may require the use of parentheses to ensure the correct order of operations. When using multiplication in loops, it is essential to ensure that the result stays within the data type's range to prevent overflow, which can lead to unexpected results.