Your words, punched.
Before text/plain there was cardboard — type a line and see it cut in real IBM 029 keypunch code.
12/80 columns
Letters combine a zone punch (12, 11 or 0) with a digit punch — A is 12-1, J is 11-1, S is 0-2. One card held one line of a program, and dropping the deck was the original merge conflict.
The 80-column card predates almost everything on this site: IBM settled the format in 1928, and for half a century one card meant one line. Terminals adopted the same width so screens could show a card per row — which is why 80 is still the default width of your shell, your linter, and every style guide argument.
The registry keeps the lineage: text/* is the punch card's whole family, still one line at a time.