##
* *Reflection: Relevance
Binary Code - Section 1: Introduction

This may seem like a peculiar choice for codes to focus on, but I chose it for two reasons. First, it created the most basic of connections between our electricity unit, which used simple lights and motors, to what is happening at the most basic level of a computer chip. Next, I felt that though binary encoding/decoding is happening deep under the hood of our software and hardware, it is the fundamental language by which they operate, and is important for any programmers to understand. It turned out to have one more unexpected benefit. Comparing the base two system of binary to our base ten system actually seemed to help strengthen student understanding of place value.

*Why binary?*

*Relevance: Why binary?*

# Binary Code

Lesson 5 of 6

## Objective: SWBAT read and write numbers and words written in binary form.

*31 minutes*

#### Introduction

*1 min*

I planned this lesson for my students because in order for them to be able to "Generate and compare multiple solutions that use patterns to transfer information," I needed to build up their schema with some existing solutions. Binary code is referred to in the clarification statement of the standard as "a grid of 1's and 0's."

Before I began the lesson, I wrote "100100 100101" on the board. I told my class that this was a message in a language that all computers can read, and that by the end of the day, they would be able to read this message too.

*expand content*

#### Binary Numbers

*15 min*

I had my students write the focus question, "How can you write a message written in binary?" in the science notebooks.

I began by reviewing our counting system. I talked about how we use 10 digits, (0-9) to count, and because we have 10 digits, we don't need to go onto a new place value until we use up all 10 digits. So every time we move a place value to left, it goes up by a power of 10. I then explained that computers can't read those digits. At there most basic level, they are just circuits. They only understand on and off, like a light switch. This is what a binary system means, only two choices, on or off, and we can write it using 0 or 1.

I wrote a chart with decimal on the left, and binary on the right, as you can see on Binary Numbers. I numbered the decimals 0-10, and left the binary blank. I then drew a binary place value chart, beginning on the right, and labeled it 1, 2, 4, 8, 16, and 32. I explained that if you only had 2 digits, 0 and 1, you would need to move to a new place value every time a number doubled. I had my class write these charts in their science notebooks as well.

I started them at 0. I asked how they could write a 0 with only 0's and 1's. They guessed 0, so far so good. Then 1 for 1, still good. That's where it got interesting. I asked them how they would write a two. I explained that because we already used all the digits available to us, we had to go to the next place value, so 10 has a 1 in the 2's place, and no 1's. (They were all lost at this point. You probably are too.) I asked how you could make a 3 out of 1's, 2's, and 4's, and they knew it was a 2 and 1, so I showed them we could write that as 11, 1 in the 2's place, and 1 in the 1's place. After they started to get the hang of it, I started calling on volunteers to explain it, and by the time we got to 10, they had it!

(Please note that I later realized I should have included 0's in the places to the left of the digit. This is not shown in the photo. You might count up to 10, like I did, but leave yourself space to fill in the 0's to the left.)

#### Resources

*expand content*

#### Binary Letters

*15 min*

Next I asked them to think how much more work it would be for letters, where we use 26 characters instead of only 10. I showed them how we could use a simple substitution code (Binary Letters), where 1 stood for A, 2 for B, etc., and then use binary to make the number for each letter. I proposed that since we wouldn't need the 32s place, we could use that as a marker. If the 32 place was a 0, the rest of the code stood for a number, and if it was a 1, it was a letter. You can see where I added this on the Binary Numbers photo. I returned their attention to the message I began the lesson with, and many figured out it said "hi" right away. Finally, I had them write their names in binary.

It seems a lot harder to explain here than it actually was with my kids. They were coding like champions by the end of the lesson.

#### Resources

*expand content*

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