#TECHLESSTEACHING
How Computers Work
Two tech-less teaching exercises to demystify computers
This article is the first in the #TechlessTeaching series, which encourages educators to take a tech-less approach to teaching students about computers and software engineering. When you skip the iPads, computers, and tech toys, you eliminate distractions, and the students focus on the principles. If you haven’t read the introduction, I recommend starting there.
The first two articles of the series focus on establishing a framework and foundation for future concepts. Each article begins with a goal.
Goal: Help children understand what computers are by simplifying how computers work.
I’ve seen many 3rd-5th grade lesson plans that incorporate “computational thinking” approaches, which give children a great way to problem solve. I’ll get into computational thinking in the next article, but first I think it’s important to demystify computers for children (and grown-ups!). No one should look at a computer, smartphone, or tablet and not have at least a small sense of what’s going on inside. They don’t need to be mysterious black boxes.
The problem I want to address is simple. As devices become more compact and software runs better, children lose the opportunity to relate those devices to the natural world. The devices become less intuitive, and therefore more mysterious, magical boxes. When children can’t relate how these devices work to the rest of the world, it’s more challenging to think computationally, and programming concepts seem foreign. But if computers become intuitive, if they just make sense, everything else flows naturally.
Exercise 1: Analog vs. Digital
Have the students take very simple measurements using both analog and digital equipment. For example, have them measure temperatures using both liquid and digital thermometers.
They should first take measurements with the analog tool first, then the digital. The point of this exercise is not about the values being measured, but to build observations about the equipment. That said, they should keep an eye out for when the measurements are not the same with both devices.
Discussion: Discuss the differences between the analog and digital equipment.
- Ask the kids which they like more and why.
- Ask them if they know how either of them work, or if they can guess how they work.
Analog and Digital are thought of as opposites. In actual fact, digital tools are analog tools with premium features. As technology becomes simpler, cheaper, and better, the false distinction between these two groups grows.
The reason we call something “analog” is because there is a physical analog of what we’re measuring. The period at which a quartz crystal vibrates in a watch is analogous to the passage of 1 second. When we measure temperature using an analog thermometer, we’re looking at alcohol traveling across a tube, over a distance. Alcohol’s expansion/contraction is an analog to temperature. When we stand on a bathroom scale, our body weight compresses a spring. As the spring compresses, a circular disc with weights rotates. The compression of a spring is a good analog for our weight.
Digital equipment still uses analogs. A digital scale still uses spring compression, but rather than have the compression rotate a metal disc showing different weights, the compression translates to an electric signal which is then displayed on a screen. The same goes with all the previous examples. The important takeaway here is that all tools that measure rely on real-world mechanics.
The discussion should help lead children to the conclusion that there’s no real difference between analog tools and digital, except that the digital tools are generally easier to read and therefore more precise. It’s worth covering the downsides to digital tools: they require batteries and there’s a lot more “stuff” to the equipment, so they’re generally more expensive and harder to repair.
Exercise 2: Finger-Counting Beyond 1,000
If you’ve seen the show Awake on Netflix, this exercise may seem familiar. In this exercise, you’ll need plenty of manipulable counting objects. For example, let’s take pebbles in a jar. The challenge is this: they must count the pebbles by moving them from one jar into another. They can’t write anything down, but they have to remember how many they’ve counted. The goal is to demonstrate the challenge of keeping track of a number when you have limited resources, so it’s fair game to distract them so they lose count.
Discussion:
- Ask them what tricks they have to keep count, keeping to the rule that they can’t write anything down. The discussion will likely involve some system with fingers, and toes.
- Ask if anyone can count higher than 1,000 using only their fingers.
- Make mention of the goal — that we’re trying to do a large task with very few tools. Just 10. And that’s what computers do — they’re very efficient.
- Here’s where you can show how to count in binary with your fingers. Binary-counting is a little tricky for everyone, and while the youngest kids may not fully understand the idea, they should get the basics:
Start with your left thumb, and call it “1.” Your left index will then be “2,” your left middle is then “4,” followed by your left ring as “8,” followed by “16.” Continuing to your right hand, “32,” “64,” “128,” “256,” “512.” To help them visualize this, it may be helpful to use a marker on your own fingers.
Next, explain that when we normally count with our fingers, we treat each number as the same value, 1, and we’re just adding the 1s up. So holding up three fingers is three 1s, 1+1+1 = 3. With binary counting, each finger is worth the value they’re labeled — so your left thumb is still 1, but your left index is worth 2. To count, you add up the values of any fingers that are extended.
One = Just your left thumb (“1”) extended.
Two = Just your left index (“2”) extended.
Three = Your left thumb (“1”) and left index (“2”) extended.
Four = Just your left middle (“4”) extended — be careful here, because you don’t want to be flipping them off.
Five = Your left thumb (“1”) and your left middle (“4”).
When all fingers on both hands are extended, you have 1+2+4+8+16+32+64+128+256+512 = 1,023.
Finally, ask them what the challenges are of counting this way. Even though there’s more thinking involved, it lets you calculate larger numbers with very little counters. If you had more fingers (or used your toes, or used lots and lots of light switches), you could count even higher with this same system.
Concluding Discussion
There are three key steps in computing:
- Receiving the instructions (what number to represent),
- Performing the instructions (extending fingers, flipping switches)
- Producing an output (looking at the fingers/switches, adding up the value to get the results.)
That’s what we did in both Exercise 1 and Exercise 2.
Computers are nothing more than a long list of on/off switches. Electricity flows through those on/off switches so that they can count. Because electricity moves through wires really, really fast, the counting in computers is really, really fast. When we write a computer program, we’re giving the computer instructions about which switches to turn off and on. When we use our fingers, buckets or light switches, we move a lot slower than electricity — but if we could move just as fast as electricity, we wouldn’t really even need computers.
The important and concluding point is that the system is built around a set of simple rules that we defined. Using those simple set of logical rules, computers can do very complicated calculations, produce video games, create virtual reality worlds, and even thinking machines. (We’ll get into how computers think in the next article.)
As a thinking exercise for the kids to prepare them for the next section, ask them to think about the things they do in their daily lives — chores, eating, getting from home to school, and ask them to think about the most basic set of instructions they can come up with for each one.
In the next article, we’ll dive deeper into computational thinking and continuing laying the foundation for problem solving.
