Binary

Computers are, at heart, oceans of tiny switches — each either on or off. Everything a machine does, including holding your Bitcoin, is built from just two symbols: 1 and 0. That’s binary.

Why only two?

We count in base 10 — ten digits, 0 to 9 — probably because we have ten fingers. Computers count in base 2 because their fingers are electrical: a wire carrying voltage (on = 1) or not (off = 0). Two clean states are easy to build, easy to tell apart, and hard to get wrong. Everything else is a matter of stringing enough switches together.

Counting with switches

In base 10, each place is a power of ten: units, tens, hundreds. In binary, each place is a power of two: 1, 2, 4, 8, 16, 32… To read a binary number, add up the place-values wherever there’s a 1:

• 1 = 1
• 10 = 2
• 101 = 4 + 1 = 5
• 1101 = 8 + 4 + 1 = 13

Turning letters into numbers

If computers only understand numbers, how do they store text? By agreeing on a code. In ASCII, every character has a number — “A” is 65, “a” is 97, a space is 32 — and that number is stored in binary. Type something below and watch it become the 1s and 0s a computer actually holds.