**Course Title:** Ruby Programming: From Basics to Advanced Techniques **Section Title:** Control Structures and Functions **Topic:** Loops: while, until, for, each **Introduction** Loops are a fundamental concept in programming that allow you to execute a block of code repeatedly for a specified number of iterations. In Ruby, there are four types of loops: while, until, for, and each. In this topic, we will explore each of these loops, their syntax, and provide practical examples to help you understand how to use them effectively. **While Loop** The while loop is used to execute a block of code as long as a condition is true. The syntax for a while loop is as follows: ```ruby while condition # code to be executed end ``` Here's an example of a while loop that prints numbers from 1 to 5: ```ruby i = 1 while i <= 5 puts i i += 1 end ``` This will output: ``` 1 2 3 4 5 ``` **Until Loop** The until loop is similar to the while loop, but it executes the code block as long as the condition is false. The syntax for an until loop is as follows: ```ruby until condition # code to be executed end ``` Here's an example of an until loop that prints numbers from 5 to 1: ```ruby i = 5 until i <= 1 puts i i -= 1 end ``` This will output: ``` 5 4 3 2 1 ``` **For Loop** The for loop is used to iterate over a block of code for each item in an array or a range. The syntax for a for loop is as follows: ```ruby for variable in iterable # code to be executed end ``` Here's an example of a for loop that prints numbers from 1 to 5: ```ruby numbers = [1, 2, 3, 4, 5] for num in numbers puts num end ``` This will output: ``` 1 2 3 4 5 ``` **Each Loop** The each loop is similar to the for loop, but it iterates over a block of code for each item in an array. The syntax for an each loop is as follows: ```ruby array.each do |item| # code to be executed end ``` Here's an example of an each loop that prints numbers from 1 to 5: ```ruby numbers = [1, 2, 3, 4, 5] numbers.each do |num| puts num end ``` This will output: ``` 1 2 3 4 5 ``` **Key Concepts** * While loops execute as long as a condition is true. * Until loops execute as long as a condition is false. * For loops iterate over a block of code for each item in an array or a range. * Each loops iterate over a block of code for each item in an array. **Practical Takeaways** * Use while loops when you need to execute a block of code repeatedly as long as a condition is true. * Use until loops when you need to execute a block of code repeatedly as long as a condition is false. * Use for loops when you need to iterate over a block of code for each item in an array or a range. * Use each loops when you need to iterate over a block of code for each item in an array. **Exercise** Write a program that uses each of the four loops (while, until, for, and each) to print numbers from 1 to 10. **Additional Resources** * Ruby documentation: [Loops](https://ruby-doc.org/core-3.1.0/doc/syntax/condition.html#label-Loops) * Ruby tutorial: [Loops](https://www.ruby-lang.org/en/documentation/quickstart/loops/) **Leave a comment or ask for help if you have any questions or need further clarification on any of the concepts covered in this topic.**