Here are some guidelines for making the most out of the How To Build A Simple Computer Out Of Anything activity.

The idea of this activity is to teach kids that computers do not need to be these complex unfathomable machines. Computing and computational thinking happens everywhere. When you engage with the kids in this activity make sure you remind them of that.

Motivate them

Randomness and probability are such fundamental mathematical concepts that your kids will be exposed to them no matter what they study in life. The applications of random number generation in computing are endless. It is the basis of computer security, fault-tolerance, distributed systems, and more. Not to mention exotic areas like quantum computingDNA sequencing and self-driving cars.

Give them examples of applications to keep them motivated. Especially stuff they interact with on a regular basis. One thing I tried with my son (who was five at the time) was to get him to generate 4 digits so he can set the passcode on his mom’s iPad and have her try to break the code. The fact that he had a secret in his head that was so powerful made him ecstatic! (Of course, I gave his mom the code and told her to pretend she didn’t know.)

Explaining randomness

Randomness is better explained in the context of a real application. You want to get the kids thinking along the lines of something like: “Imagine you are making a secret number for a combination lock or your iPad so a thief can’t open it. If the thief watched your computer doing work but didn’t see the numbers that came out, would he be able to guess the numbers if he repeated what you did?”

After they do the activity for a while and if you feel the kids are advanced enough, you may follow with questions about the quality of the random numbers. Are they truly random (well-distributed)? Can a “thief” easily guess them if he ran the computer a few times and picked the most popular outputs?

No computing in their heads

One thing that will likely happen is the kids will come up with a design where the random number is created by their own decision. That’s “cheating” so to speak. For example, their design might be to flip a card from a set of cards laid out on the table. They select the card, flip it and write down the number on the card. This is not a good design because they chose (in their head) which card to flip. So, keep reminding them that they can’t “choose” by themselves. The computer has to “choose”. A good design will involve actions that create entropy like mixing a bunch of things, throwing stuff in the air, or pushing or smashing something.

Help but don’t interfere

I’ve seen kids do all kinds of designs. From throwing a bouncy ball around the house to elaborate arts-and-crafts projects like a fully colored wheel-of-fortune. As long as the kids don’t compute the random numbers in their heads, let them be creative. The more they enjoy building and using their computer the more engaged they’ll be. Don’t hesitate to give them ideas to make their computers more “extravagant”.

More designs to play with

After the kids have designed their own, a great follow up exercise is to give them the “computing” materials first and then ask them to design a random-number generating computer using only the provided materials.

Here are some ideas on how to build a computer using only:

  • A bouncy ball.
    • How: drop it in the air and count how many times it bounces.
  • A long string.
    • How: drop it in the air. When it lands, count the number of times it crosses with itself.
  • A measuring tape with any of the above.
    • Measure distance travelled, length, width etc.


Use your phone and post pictures of your kid’s designs to the DrTechniko Facebook Page. I will personally respond to your posts.

Also, don’t hesitate to send me a personal message via the Facebook page if you need help.

I hope we learned something useful today,