How computers make decisions: the binary truth nobody tells you

The Light Switch in Your Hallway

Let me tell you a story about your hallway light switch. You've probably flipped it thousands of times without thinking twice about it. Up, the light comes on. Down, the light goes off. Simple, right?

That humble light switch, the one you barely notice, holds the secret to how every computer in the world works. Not sort of. Not metaphorically. Actually, literally, completely.

You see, that switch can only be in two positions: on or off. Never halfway. Never "sort of on." Either electricity flows and the bulb lights up, or it doesn't flow and your hallway stays dark. Two choices. That's it.

And from these billions of simple yes-or-no, on-or-off switches, we get everything:

All of it comes from switches turning on and off really, really fast.

Sound too simple to be true? Stay with me. I'm going to show you how something as basic as a light switch creates what looks like magic.

The Restaurant Problem

Imagine you're calling your favorite restaurant to make a dinner reservation. The person who answers starts asking you questions:

Now imagine a different call:

Notice what just happened? The restaurant staff made a decision about where to seat you, or whether they could seat you at all, by asking simple yes-or-no questions. Each answer was binary: yes or no. And based on those answers, they made what seems like a complicated decision.

That's exactly, and I mean exactly, how your computer makes every single decision. It asks millions of yes-or-no questions, incredibly fast, and uses the answers to decide what to do.

Complex decisions, made from piles and piles of simple yes-or-no questions, answered faster than you can blink.

Why Only Two? The Three-Way Light Switch That Ruined Everything

You might be wondering: why only yes and no? Why not have three options? Or ten? Wouldn't that make computers smarter?

Here's a story that explains why that doesn't work.

Back in the 1940s and 50s, when people were first building computers, some engineers thought, "Hey, why limit ourselves to on and off? Let's make switches with three positions: off, medium, and on!"

Seemed clever. More options, more power, right?

It's like asking someone "Are you home?" versus asking "On a scale of 1 to 10, how home are you?" The first question has a clear answer. The second is just confusing.

So computers use two positions, on and off, because it's the only way to make something reliable. And we call those two positions "1" and "0" or "yes" and "no" or "true" and "false." Different words, same idea: binary. Two choices.

The Secret Patterns: How Yes and No Build Everything

Okay, so we have billions of switches that can be on or off. How do we get from there to, say, recognizing your voice when you ask your phone for tomorrow's weather?

The secret is in combining switches into patterns that answer specific kinds of questions. Let me show you a few, using things you already know.

The Bank Vault: Both Keys Required

You know how in movies, the bank vault needs two people with two different keys, and both have to turn their keys at the exact same time for the vault opens?

That's one pattern computers use constantly. They check: is condition A true AND is condition B true? Only if BOTH are yes does the computer say yes.

The House With Two Doors: Either One Works

Now imagine your house has a front door and a back door. You can get in if the front door is unlocked OR if the back door is unlocked OR if both are unlocked. You just need at least one way in.

That's another pattern. The computer checks: is condition A true OR is condition B true? If at least one is yes, the computer says yes.

The Opposite Day: Flip It Around

Remember playing opposite day as a kid? Everything means the reverse of what it normally means.

The Staircase Lights: The Switcharoo

Here's my favorite because I bet you've used it without realizing what it teaches us about computers.

You know staircases with light switches at both the bottom and the top? You can flip either switch to turn the light on or off. Walk upstairs in the dark, flip the top switch, light comes on. Walk back down, flip the bottom switch, light goes off.

And there's a flip side to this: checking if two things are the SAME. Like matching passwords, or checking if your face today looks like your face yesterday. Same? Yes. Different? No.

These simple patterns, these simple ways of combining yes-or-no answers, are the building blocks of everything your computer does. Everything.

Your Morning Coffee Machine (And How It's Smarter Than You Think)

Let's talk about something you probably use every morning: a coffee machine. The simple kind with a timer.

You fill it with water and coffee grounds before bed. You set the timer for 7 AM. You go to sleep. And like magic, you wake up to fresh coffee.

How does the machine know when to start brewing?

It's asking yes-or-no questions, constantly, all night long:

Thousands of times per second, the same question. And the instant the answer changes from no to yes, the machine acts.

Your computer does the same thing, but with millions of questions happening simultaneously:

Millions of yes-or-no questions, asked billions of times per second, and the computer reacts the instant any answer changes.

That's why your phone seems so responsive. It's not actually smart. It's just asking questions really, really, really fast.

The Difference Between Expensive and Cheap (That Nobody Tells You)

Here's something that might surprise you: not all ways of asking yes-or-no questions cost the same.

Imagine you're trying to figure out if you have enough money to buy something. You could:

Both get you an answer. But Option A takes way more time and effort, right?

Computers face the same choice. For some tasks, they can take the quick glance approach: fast, simple, uses barely any battery. For other tasks, they do the slow, precise, count-every-penny approach: accurate, but uses lots of battery and takes longer.

Some companies (like Dweve and a few others) are building systems that use the quick way whenever it makes sense. The result? Your phone battery lasts days instead of hours. Your apps respond instantly instead of lagging. And your personal data can stay on your phone instead of being sent to some company's servers.

Same results, way more efficient. All because they're using simple yes-or-no questions instead of complicated calculations.

When Your Phone Recognizes Your Face (The Everyday Miracle)

Let's talk about something that seems like magic: unlocking your phone by looking at it.

When you first set this up, your phone takes a few photos of your face. But here's what it doesn't do: it doesn't store those photos. Instead, it looks at your face like a friend who's trying to remember you.

Then it turns all those observations into a pattern. A fingerprint, but for your face.

Later, when you want to unlock your phone, the camera looks at you again. It measures the same things. And then it plays the matching game we talked about earlier:

Thousands of these checks, incredibly fast. And if enough answers are yes, the phone says, "That's the same person!" and unlocks.

Not enough matches? "That's someone different," and it stays locked.

And because it's all yes-or-no questions (is this feature the same as the stored one?), it can happen right on your phone. Fast. Private. No internet needed. Your face pattern never leaves your device.

That's the power of simple yes-or-no questions, done really, really fast.

What This Means for Your Daily Life (The Practical Stuff)

Okay, so computers use yes-or-no questions to make decisions. Neat. But why should you care?

Because it affects things you deal with every single day.

These aren't future benefits. This is happening now. Better software is being built that respects how yes-or-no questions actually work.

The 100 Billion Decisions You Didn't Notice

Want to hear something wild? While you've been reading this article, your computer has made about 100 billion decisions.

Not an exaggeration. Your device is checking things billions of times per second. Is the screen being touched? Is there new data arriving? Should this letter appear in this color? Is the user scrolling? Should we load more text? Is it time to check for new emails? Is the battery okay?

All happening so fast you don't notice. All yes-or-no questions, billions of them, working together to create what you see.

It's just billions of tiny switches, asking yes-or-no questions, following rules we humans designed. Simple questions, answered incredibly fast, creating the illusion of something smart.

Which, when you think about it, is more impressive than if it were actually smart. Because we built this. Regular people, using ideas and engineering, created machines that make billions of perfect decisions per second using nothing more complicated than light switches.

Why This Started With a Light Switch

Remember when I told you about your hallway light switch at the beginning? Now you know why I started there.

That switch can only be in two positions. On or off. And that limitation, that simplicity, is exactly why it works reliably every single time you flip it.

Your photos. Your messages. Your maps. Your banking. Your video calls with family. All of it, at the deepest level, is just switches flipping on and off, asking yes-or-no questions, billions of times per second.

It's not magic. It's something better than magic. It's human ingenuity taking something as simple as a light switch and building the modern world with it.

What You Need to Remember

If this feels like a lot, here's what matters:

1. 1 Computers use yes-or-no questions for everything. Every decision, no matter how complex it seems, is built from millions of simple yes-or-no answers. Like that restaurant reservation, but millions of times faster.
2. 2 Simple is reliable. Two positions (on/off, yes/no) work perfectly every time. Three or more positions would be unreliable and cause mistakes. That's why every computer ever built uses binary.
3. 3 Patterns combine to make complexity. Those five patterns we talked about (bank vault, two doors, opposite day, staircase, matching game) combine in billions of ways to make everything your computer does.
4. 4 Not all approaches cost the same. Some ways of computing use way more battery and time than others. The most efficient way is often the simplest: quick yes-or-no checks instead of complicated calculations.
5. 5 This affects your daily life. Battery life, privacy, speed, environmental impact, cost. All of these are directly influenced by whether your apps use efficient yes-or-no computing or wasteful complicated calculations.
6. 6 Simple yes-or-no computing enables privacy. When things are efficient enough to run on your phone, your data never needs to leave your device. No cloud. No sending your photos or voice to company servers.
7. 7 The future is going back to basics. After years of doing everything the complicated way, smart engineers are realizing: for many tasks, simple yes-or-no questions work better, faster, and more efficiently.

The Bottom Line

Your computer, whether it's your phone or your laptop or any other device, makes billions of decisions every second. And every single one of those decisions comes down to yes or no, on or off, 1 or 0.

It's not more complicated than your hallway light switch. It's just billions of those switches, working together, incredibly fast.

This isn't future technology. It's happening now. Your next phone, your next app update, might already use these efficient yes-or-no approaches.

And it all traces back to something as simple as a light switch. On or off. Yes or no. The simplest possible choice, repeated billions of times per second, creating everything you think of as the digital world.

So next time you flip your hallway light switch, remember: you're using the exact same idea that makes your smartphone smart. Simple, reliable, and somehow, absolutely brilliant.