In article by Warren Toomey:
P.S. Does anybody want to backport vi to 6th and 7th
The 2BSD tape contains vi source code that can *definitely* be built
on 7th edition (I've done it, it was easy) and supposedly can also
be used to build a 6th-edition "native" vi if you're willing to
backport the V7 C compiler (I haven't done that yet).
Since many people in 2BSD's time frame would not have had access
to V7 systems or V7-ish C compilers, the 2BSD tape also contains a
vi binary for V6 systems.
I think 2BSD was released around the same time as V7, and had an
assumption that many people would not yet have access to V7, and
so would want to use 2BSD as an add-on to V6 systems.
Since 6th edition didn't have environment variables, the 2BSD/V6
version of vi would get the terminal type from a file that mapped
hardwired serial lines to terminal type names. I think it was
By the way, does anybody else think that vi should have been upgraded
to vii when V7 came out? :-)