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How Computers Store Everything

Flip switches into numbers, letters, pixels and sound, then squeeze, fix and hide them.

Intermediate · 11 lessons · Free, no account needed

Best after: How a Programmer Thinks

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Lessons

1. Switches Count (5 min): A bit is one switch: 0 (off) or 1 (on).
2. Bytes and Overflow (7 min): A byte is 8 bits. It holds 2⁸ = 256 values: 0 to 255.
3. Letters Are Numbers (7 min): Every character has a number, its code: A is 65, a is 97.
4. Pixels and Colors (7 min): A picture is a grid of pixels, each one a single colour.
5. Sound Is a List of Numbers (7 min): A microphone turns sound into a wave; a computer samples it: measures its height again and again.
6. Squeezing Without Losing (7 min): Compression writes the same information in fewer characters.
7. Throw Away What You Won't Notice (7 min): Lossy compression throws away detail you are unlikely to notice, forever.
8. The Parity Magic Trick (7 min): A parity bit is an extra bit that makes the number of 1s even.
9. Fixing Errors on the Fly (7 min): Error correction adds spare bits so the receiver can find and fix flipped bits itself.
10. Secret Messages (7 min): Encryption turns a message into gibberish that only someone with the key can undo.
11. Hide a Message in a Picture (7 min): Steganography hides that a message exists at all, not just what it says.

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