Warm Up (10 min)

Introduction

Use "while" in a sentence in front of the students. Ask the students what the word "while" means. If you were to say "while there is a hole, fill it with dirt" what would they do? How long would they do that?

When you use a word like “while”, you are relying on a condition to tell the computer how long the loop should run. A condition is a statement that is tested and found to be true or false. In the case above, the condition is if there is a hole. It’s only possible for there to be a hole or for there not to be a hole, thus the statement is only ever true or false.

Tell the students they will be learning about a new kind of loop. Previously, students only used loops to repeat a command a certain number of times. Here, they won't always know how many times to repeat the command, however, they will know when to stop or when to keep going. While loops allow the programmer to repeat a command as long as a condition is still true. In the previous example, the condition is the existence of a hole.

If there's time, have the students discuss other times using a while loop would be useful. Examples include:

• Running toward a ball while it is in front of you.
• Filling a glass while it has space for more liquid.
• Walk forward while there is a path ahead.

Main Activity (30 min)

CSF Express Course 2018 - Website

While loops are not always a difficult concept for students to understand, but if you think your class might struggle with these puzzles, we recommend Pair Programming - Student Video. This will allow students to bounce ideas of each other before implementing the code. Pair programming works to increase confidence and understanding with topics like while loops.

Wrap Up (15 min)

Journaling

Having students write about what they learned, why it’s useful, and how they feel about it can help solidify any knowledge they obtained today and build a review sheet for them to look to in the future.

Journal Prompts:

• What was today's lesson about?
• How do you feel about today's lesson?
• What is the difference between a while loop and a normal repeat loop?
• Give an example of a puzzle where you would use a while loop, but not use a repeat loop. Can you give an example of a puzzle where you would use a repeat loop, but not a while loop?

Extended Learning

While Simon Says

Go out to a large playing field and have the students stand in a line facing you. Make sure every student can see you. Declare a couple of while loops such as:

• While my right hand is up, you can walk toward me
• While I cover my eyes, you can skip toward me
• While my head is turned to the right, you have to walk backwards

The first student to get to you wins. If there's time, let other students be "Simon" at the front of the class.

Bridging Activity (15 min)

This activity will help bring the unplugged concepts from "Conditionals With Cards" into the online world that the students are moving into. It will also help bridge the concept of conditionals to a new type of loop- while loops. Choose one of the following to do with your class:

Unplugged Activity Using Paper Blocks

Print and cut out 2-3 while / do blocks and blank action blocks from Unplugged Blocks (Courses C-F) - Manipulatives and pull out a deck of cards. Ask the class to come up with a couple of conditionals to use with the deck of cards like they did in "Conditionals with Cards." This time, instead of using the conditional in an if / else statement, they will be using it in a while loop.

When the conditionals have been decided on as a class, fill in the blank part of the while block with the various card groups that the kids came up with. Examples include "Even Numbered", "Red card", or "Diamonds". Fill in the action blocks with the actions the students came up with. Make sure the students know the action blocks need to be directly inside the while block. Line the blocks up sequentially so students can see how it runs as a program.

Below is an example.

Now shuffle the deck of cards and play "Conditionals with Cards" again. Flip through the deck card-by-card, reacting to cards if a conditional has been made for it. To maintain authenticity for this while loop experience, make sure you hold up the selected card for a good long while to give students time to react over several beats. Feel free to jump back to previous cards to get the point across that once you have left a while loop, you continue moving forward and do not return to the previous loop just because the conditions match again.

Preview of Online Puzzles

Pull up a puzzle from CSF Express Course - Website, we recommend Puzzle 6.

• Ask the class what the farmer should do when she gets to the pile of dirt.
  • The farmer should use a conditional in a while loop to check if there is a pile.
• Use the while there is a pile / do block. Ask the class what the farmer should do if there is no pile. When should the farmer stop?
  • The farmer should remove 1 if there is a pile. The while loop will continue until there is no pile, so then your code is finished!

Fill in the rest of the code and press Run. Discuss with the class why this worked.