If I recall, we got the typesetter (troff) tape in between V6 and the later (I think we
got PWB next then V7). It had a compiler on it. I presume that it was needed to
compile troff, but most of us installed it as a more up to date C compiler. If I recall
properly (and boy my mind is hazy on this), is that it supported the “new” += syntax while
warning that =+ was deprecated.
At some point, the structure elements being made unique to the structure they were defined
in, and the ability to assign/pass structures got supported, though I thought that was the
compiler that came with V7.
I’m still annoyed they didn’t fix arrays when they fixed structs.