In article by Warren Toomey: 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 called /etc/htmp. By the way, does anybody else think that vi should have been upgraded to vii when V7 came out? :-)