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Binary
Why computers count in ones and zeros, and how that makes words, pictures and music.
The short version
Binary is a way of writing numbers using only two digits, 0 and 1. Computers use it because a switch has two states, on and off, and that is easy to build reliably. Any number, letter, picture or sound can be turned into a long string of ones and zeros. It builds on how a computer works.
I always thought binary was a code someone had to translate.
It is only counting, using two digits instead of ten.
Same idea, fewer symbols.
Counting with two digits
In everyday counting we have ten digits, and each place is worth ten times the one to its right: ones, tens, hundreds. In binary, each place is worth two times the one to its right: ones, twos, fours, eights.
So 5 is one four, no two, and one one, which is written 101. And 10 is one eight, no four, one two, no one: 1010.
Bit and byte
A bit is a single 0 or 1. A byte is eight bits, enough for a number from 0 to 255 or one basic ASCII character. Most modern text uses UTF-8, where a character can take one to four bytes.
Anything can be numbers
Text: each letter has a number. Capital A is 65, which in binary is 01000001. A word is a list of these.
Pictures: a photo is a grid of dots, and each dot has numbers for how much red, green and blue it has.
Sound: a recording measures the air pressure thousands of times a second and stores each measurement as a number.
Once it is numbers, it is bits, and a computer can store, copy and send it.
8 billion
Roughly how many bits there are in a gigabyte, which is a thousand million bytes of eight bits each. A short phone video can fill several of them.
Source: Unicode FAQ on UTF-8 explains how text characters are encoded as bytes.
Key takeaways
- Binary uses only 0 and 1.
- Each place is worth twice the one before.
- A byte is eight bits; text characters can use more than one byte.
- Text, pictures and sound are all stored as numbers.
Now you know.
Binary is counting with two digits.
A switch is on or off.
Everything is stored as numbers.
Last reviewed 3 Nov 2026
