What I remember, there was first roff written in assembler. It was

then rewrittn into C (but now with real macro capabilities. roff

has a lt build in), Typesetter C appeared in Edition 6.1 (of 6.2)

since the n/troff code demanded a lot from the C-compiler. To make

it possible to run it on a pdp11 there was the hack turning data

into test (for the hyphenation tables). Ditroff was done by bwk

to be devie independent.