which of the following loop runs until a statement becomes true?

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06-10-2024

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In programming, loops are a fundamental concept that allows us to execute a block of code multiple times. Among various types of loops, one common question arises: Which loop runs until a statement becomes true? In this article, we'll explore the different types of loops, specifically focusing on the while loop, which continues running until a specified condition evaluates to true.

What is a Loop?

A loop is a control structure that repeats a block of code as long as a specified condition is met. This repetitive action is beneficial for tasks that require iteration, such as processing elements in a collection, performing calculations, or handling repeated user inputs.

Types of Loops

Before diving into which loop runs until a statement becomes true, let's briefly discuss the various types of loops commonly used in programming:

1. For Loop: This loop is used when you know in advance how many times you want to execute a statement or a block of statements. It’s typically used for iterating over arrays or collections.

   Example in Python:

   for i in range(5):
       print(i)
   

2. While Loop: This is the loop that continues to run as long as the condition is true. It checks the condition before executing the loop's body, making it particularly useful when the number of iterations is not known beforehand.

   Example in Python:

   i = 0
   while i < 5:
       print(i)
       i += 1
   

3. Do-While Loop: This type of loop guarantees that the loop's body will be executed at least once, as it checks the condition after the execution. This type is less common in some languages but is still essential to understand.

   Example in JavaScript:

   let i = 0;
   do {
       console.log(i);
       i++;
   } while (i < 5);
   

The While Loop: Running Until True

Out of these, the while loop is the one that runs until a specified condition becomes false. Here's how it works:

Syntax:

while condition:
    # Block of code to be executed

Practical Example:

Let's consider a simple scenario where we want to prompt a user to enter a password until they provide the correct one. We can achieve this using a while loop:

correct_password = "password123"
user_input = ""

while user_input != correct_password:
    user_input = input("Enter the password: ")
    if user_input == correct_password:
        print("Access granted.")
    else:
        print("Access denied. Try again.")

In this example, the while loop continues to prompt the user for input until they enter the correct password. The condition (user_input != correct_password) ensures that the loop runs as long as the password is incorrect.

Why Use a While Loop?

The choice of a while loop is particularly useful when:

• The number of iterations is unknown at the outset.
• You need to continue looping based on user input or external conditions.
• You want to ensure that the loop can end based on a logical condition rather than a fixed count.

Conclusion

To summarize, the loop that runs until a statement becomes true is the while loop. This structure is invaluable in programming as it allows for flexible and controlled repetition of code. Understanding when and how to use different types of loops is essential for effective coding.

By grasping these fundamental concepts, you not only enhance your programming skills but also improve your ability to solve complex problems efficiently.

Further Reading

For a deeper understanding of loops in programming, consider checking the following resources:

• W3Schools: Python Loops
• MDN Web Docs: JavaScript Loops
• GeeksforGeeks: Control Flow

By exploring these links, you can enhance your knowledge and become more adept at using loops in your programming endeavors.

Attribution: This article was inspired by various discussions and examples found on GitHub and coding forums. For specific queries, you can refer to the original discussions.