hello, world

Curator’s note

Eight instructions: move left, move right, add one, subtract one, read a byte, write a byte, and a pair of brackets that loop while the current cell is not zero. That is the whole language, and it is Turing complete.

Nothing here mentions a letter. The opening ++++++++[>+++++++++++++>++++<<-] is arithmetic: it counts eight down to zero, and on each pass adds thirteen to one cell and four to the next. Eight thirteens is 104, which is h. Eight fours is 32, which is a space. Everything after that is small corrections from those two anchors.

So the program keeps two fingers in the ASCII table — one parked among the lowercase letters, one down in the punctuation — and hops between them. --- walks h back to e. +++++++ walks on to l, which is then printed twice for the price of one extra instruction. The comma costs a jump to the second cell and twelve additions; coming back, w is still only eight away from the o we left behind.

Read that way the program is not spelling a message at all. It is a route, and the message is the order in which it visits the letters. The shortest such route is a genuinely interesting problem, which is why people still golf this program thirty years on.

Every character outside +-<>[]., is ignored by the language, so a Brainfuck file can carry its own explanation and still run. This one is kept bare.