Binary code translator

Text on the left becomes binary on the right, eight digits to a byte. Swap the boxes with the arrows to go from binary back to English; spaces, commas and 0b prefixes are ignored when decoding, so an unbroken run of digits works as well as neat groups.

Separator changes what sits between bytes in the output. Set it to None when you're pasting into code rather than into a message.

Every character has a number in the Unicode table. Write that number in base 2, pad it to eight digits, and you have a byte. Capital A is 65: 01000001. Lowercase a is 97: 01100001. The difference is 32, a single bit. ASCII's designers put the lowercase letters there on purpose, because one bit made case-insensitive matching easier and keyboards simpler to build.

Characters past the first 128 need more than one byte. UTF-8 spends two on most accented letters, three on most symbols and CJK characters, and four on an emoji. One of those produces 32 digits.

Gottfried Leibniz published binary arithmetic in 1703, long before any computer, and he wasn't chasing an application: he took a system where everything could be written with 1 and 0 as a demonstration of creation out of nothing.

The eight-bit byte is much newer and much more arbitrary. Many early machines grouped bits in sixes. IBM chose eight for the System/360, announced in 1964, because it held two decimal digits neatly and left room for a bigger character set, and the industry followed. Nothing in nature requires it.

Binary is the most verbose way to write bytes down. Base64 and hexadecimal carry the same bytes in far fewer characters, and they're what you meet in real files and headers.

For the number of each character rather than its bytes, use character codes or Unicode code points. And Morse builds a whole alphabet out of two states, the same way a byte does.

Ages 9 and up, about 30 minutes. Give five students a card each showing 16, 8, 4, 2 and 1 on one side and blank on the other. Call out a number and have them flip cards so the shown values add up to it: that row of cards, shown as 1 and blank as 0, is the number in binary.

Take it further: use the five cards to spell letters, with A as 1 up to Z as 26, then compare with the 8-bit codes computers use for text in the translator above. The binary alphabet chart prints for reference.