Activity Day Girls Craft Idea: Binary Code Necklace

1966212_10153976095495274_3982796096946077944_oHere’s a computer science lesson and craft activity that speaks to my geeky heart.  I do it with groups of all ages, and it would be perfect for Activity Day girls. It could also work for Cub Scouts, perhaps with a hemp cord for a masculine look. It was inspired by the “Hour of Code” event last year. The lesson plan by Thinkersmith is excellent,  and covers everything you need to know. It is comprehensive enough for someone without any computer science background to run the activity successfully. I’ll summarize a few points here, but you should go read it. The necklace craft was my own addition. My daughter is modeling her necklace in the photo at left.

Background: Everything is numbers!

To introduce the project, the lesson plan includes background information such as photos of what computer components look like inside and how computers store data on DVDs. Inside a computer, EVERYTHING is numbers–specifically, binary (base-2) numbers. As far as the computer is concerned, the above photo of my daughter is just a bunch of binary numbers. This blog post, your grandma’s voice and face on Skype, all the movies you watch on Netflix–all these things are just binary numbers. The computer doesn’t actually distinguish between these things in storing the data or performing computations on it in the CPU. Software imposes our human interpretations on the data–it could interpret the exact same binary number as a high pitch sound in one case, as a shade of dark green in another, and in yet a third case as a letter of the alphabet. When people agree on what interpretation we want to impose on different collections of binary numbers, it gives them meaning in that context. We call these agreed-upon interpretations encoding schemes or just encodings. This activity explores an encoding named ASCII, which is one common way of interpreting binary numbers as letters of the alphabet.

The ASCII Code

The ASCII code for capital letters is shown below. Unlike base-10 numbers, which can have the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, binary (base-2) numbers can only have the digits 0 and 1 (we usually call the binary digits bits). On this cheat-sheet card, the white squares represent 1 and the black squares represent 0.


Using this card, you can see that the word “CAT” would be spelled 01000011 (C) 01000001 (A) 01010100 (T). ASCII is also able to encode lower-case letters, spaces, and some punctuation, so you can refer students who are interested in those to a complete ASCII table.

Writing your name

The craft activity involves letting the students make a stylish necklace for themselves, where their names are spelled out in binary using black and white beads. To prepare for beading, the lesson plan includes printable worksheets where kids can color in squares to spell out their names. There are two versions of the worksheet: one with very large boxes for smaller kids, and one with smaller boxes for older kids (and longer messages). Here is what the younger version looks like (each row is one letter, because ASCII encodes each letter with 8 bits):


Making the necklace

After the students have spelled out their names on paper, let them write out the letters with beads to make a necklace. Here is my daughter’s necklace. She used glow-in-the-dark beads to separate each letter. In computer science, we call special separating markers like this delimiters. Many encodings use delimiters, especially if the size of each unit can vary. Of course, you don’t actually need a delimiter to know when one character ends and another begins in ASCII (assuming you know the start of the whole message), because the size of each character doesn’t vary–we can always rely on each character using exactly 8 bits.


I hope you are able to use this activity to inspire a love for computer science in some special kid in your life: those you lead, your own child, a neighbor or friend’s kid, a grandchild, a niece or nephew–just to name a few ideas. Give the gift of geek!


Thinkersmith materials used in this post are made available under a Creative Commons attribution, noncommerical, sharealike license. Please credit their work if you reuse!


Other Primary lesson ideas:


  1. I’m fifth grade art mom this year and we’re definitely going to do this. Thanks!

  2. Mark Brown says:

    where’s the pink?

    A great idea, CBL. Many wards also have people who work with computers, so it might be possible to arrange a field trip.

  3. Thanks for this great idea!

  4. Great idea. Its never too early to try and explain to kids how computers work so they aren’t such a mystery (spoken as a former computer programmer). And what a fun craft to reinforce the idea!!

  5. Kevin Barney says:

    What a fantastic idea!

  6. kristine a says:

    My 9yo girl who has a modesty activity day next month says: AWESOME!

    This is perfect because kids these age really like the magic/code/spy thing…. So she thinks this is very fun.

  7. I’m getting set to teach samurai-style swordfighting to the Activity Day girls. The Young Women did it a couple of months ago, and it was a huge hit.

    One night when no leaders showed up, I got to teach Activity Day. We went into the attic and learned about HVAC engineering. One HVAC engineer makes more money than the entire cheerleading squad for our local pro football team. To this day, I can still ask them what HVAC means, and they all know. Plus, it’s really cool going into the attic.

  8. Oh, Cynthia, this wins on so many levels!

  9. I just started a Girl Scout troop – I know what our next activity is going to be!

  10. I’m so excited to hear reports that folks are planning on doing this in different venues! Let me know if you have any questions or your own cool additions or any other feedback.

  11. Rather than sending the link to our Activity Days leader, I should probably prep it and volunteer to teach it myself. It sounds great. As an aside, can we get some details on the Samurai sword fighting, Michael? That also sounds like a win!

  12. When you’re finished with that, you can get a deck of cards and teach them the code from Crytonomicon. And then let them spend the rest of the evening encoding a message to send to their secret friend.

  13. I’d suggest “kendo” using bamboo “swords” rather than real katana. You may get some bruises, but no blood.

  14. it's a series of tubes says:

    One HVAC engineer makes more money than the entire cheerleading squad for our local pro football team.

    in fairness, this is only because the squad works essentially for free. I work with a former member of our local pro squad, and she was paid less than $1000 per season.

  15. My son and daughter are both super pumped to do this.

    I’ve volunteered to teach simple programming and/or HTML to both the YW and AD leaders in our ward, with no luck so far.

    The scouts, meanwhile, have made a video game. :(

  16. Thank you for sharing this. My daughter’s YW leaders are great people and I know they will want to do this. My daughter is looking forward to doing this, and she is very computer literate.

  17. I love this idea, Cynthia! What a great way to introduce kids to some big ideas! Thanks for sharing this.

  18. On sword fighting:
    My daughter and I have a collection of foam-covered swords for dueling – we’ve picked these up over the years from attending anime conventions and working as storytellers at renaissance fairs. Figure PVC-pipe about 4 feet long, with some pipe insulation or a foam pool noodle over it with a handle left at one end. Stretch over a leg from some girls tights, duct-tape it down at the handle, and you’re set.

    For Young Women, my daughter had a quick presentation on the principles of Bushido and how they relate to Young Women’s values. Fight with honor, protect the weak, and so forth. For the rules, combatants bow to each other, tap swords, and the ref says “Ah-jee-may”, which is Japanese for “Start the fight”. Blow to the body and you’re dead. Blow to the leg, and you’re dead. Blow to the arm, and the person who got hit has to switch to the other arm. Head shots are against the rules, so if you hit the other person in the head, you lose the point. When the point is scored, both fighters return to their starting point and go through the bow, tap, ajime again. You have to have rules when you fight, otherwise it’s just wailing on each other like two four-year-olds cracked out on Halloween candy.

    The finest moment of the night was when the 2nd counselor in our Bishopric was battling his 12-year old daughter. “I love you so much, I will take your head.”

    My theory is that once in a while, the girls need to have an activity that makes the boys jealous. When YW activities consist of cooking, planning meals, writing a letter to a future husband, and spa night, my daughter does her best to control her outrage. Even the Quran lists archery and astronomy as acceptable pursuits for young women.

  19. I think it’s time we made some of these swords for the YW–

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