This was awarded "Best of Show - abuse of libc" at the time[0]. See also the judges' remarks[1]:
This program consists of a single printf(3) statement wrapped in a while loop. You would not think that this would amount to much, but you would be very, very wrong. A clue to what is happening and how this works is encoded in the ASCII art of the program source.
Alex: "Its primary purpose is to serve as The One True Debugger."
(It has certainly served me well.)
It was unintentional, but Ken Thompson being Ken Thompson, can't be 100% sure.
It was probably unintentional, yeah, I don't recall any mentions of early printf being overloaded to do stuff, nor is it clear why you would do that since you're using it in a much more convenient Turing-complete language already (C).
