differences in UNIX versions

[gwyn at BRL-VLD.ARPA]

From:      Doug Gwyn (VLD/VMB) <gwyn at BRL-VLD.ARPA>

A list of all the differences between 7th Ed., 4.1BSD, 4.2BSD, Sys. III,
and Sys. V UNIXes would fill a book.  The only simple one is that very
little user-visible change occurred from UNIX System III to System V,
except by adding upward-compatible extensions (the main visible change
that was incompatible was in what uname() returned).  If you have
specific requirements, feel free to ask them, but a list of all
differences seems pretty useless since there are so many.