💡 Everything is a light switch

Deep down, a computer only knows two things: off and on. That's it. No letters, no colors, no songs — just billions of microscopic switches, each one either off or on. We write them as 0 and 1.

Why so limited? Electricity. "Is the current flowing or not?" is a question a machine can answer perfectly every time, billions of times a second. Ten different voltage levels would get misread; two never are.

But how do you count to 100 with switches that only know 0 and 1? With a beautiful trick: give each switch a value, and double it each time — 1, 2, 4, 8, 16… Turn on the right combination and their values add up to any number you want. Try it:

A row of 8 switches is called a byte — the basic unit of everything digital. One byte can hold any number from 0 to 255. A "gigabyte" is simply a billion of those rows. Every photo, song, and message on your phone is nothing but bytes: rows of light switches, off and on.