You scan a candy bar at the store — beep! — and the computer knows the price, the flavor, even how many are left in the back room. All that from a few black lines? How does a barcode squeeze so much information into such a tiny space?

Here's the trick: a barcode doesn't actually hold very much information at all. Those black and white stripes are just a number — usually twelve or thirteen digits long. Think of it like a locker number at school. The number 247 doesn't tell you what's inside the locker. It just tells you which locker to open.

When the scanner reads the barcode, it sends that number to a computer. The computer looks up the number in a giant database — a huge digital filing cabinet that stores information about millions of products. "Ah, number 041000000000! That's a pack of mint gum, costs $1.29, we have 47 in stock."

So the barcode itself is tiny and simple — just a number written in a language scanners can read. The WIDTH of each black stripe and each white space stands for a different digit. Thin stripe, thick space, thin stripe, thick stripe — that pattern might spell out "4." A different pattern spells out "7."

The scanner shines a red laser across the barcode. Black stripes absorb the light — no reflection. White spaces bounce the light back — bright flash. The scanner reads the pattern of dark-bright-dark-bright like Morse code, translating flashes into numbers faster than you can blink.

Now here's where it gets clever. The barcode has a built-in mistake-catcher called a "check digit." The last number is calculated from all the others using a special math formula. If the scanner reads the barcode and the math doesn't match, it knows something went wrong — maybe the barcode is smudged or wrinkled — and it asks you to scan again.

Different products around the world share the same system, so a barcode from Japan works on a scanner in Brazil. Every company gets its own range of numbers to use, like getting assigned a section of phone numbers. No two products ever end up with the same code.

Some newer barcodes — QR codes, those square pixelated patterns — DO hold more information directly inside them, like tiny pictures made of data. But the classic barcode? It's just a number, brilliantly disguised as stripes. The real magic happens in the computer that remembers what each number means.

So next time you hear that beep at the register, you'll know: the barcode whispered a number, the computer looked it up in its massive memory, and in a fraction of a second, your candy bar got a price tag. All that information was never IN the tiny stripes — it was waiting in the database, ready to be unlocked with the right key.