Path: utzoo!attcan!uunet!auspex!guy
From: guy@auspex.UUCP (Guy Harris)
Newsgroups: comp.os.misc
Subject: Re: System V, Release 4
Message-ID: <26@auspex.UUCP>
Date: 19 Oct 88 17:00:07 GMT
References: <64481@felix.UUCP>
Reply-To: guy@auspex.UUCP (Guy Harris)
Organization: Auspex Systems, Santa Clara
Lines: 37

>As well as changing the file formats (to BSD fast file system),

It supports both the V7 file system, as used by current S5 releases, and
the BSD file system, under the VFS (Virtual File System) interface
(basically the SunOS 4.0 VFS, with some assorted changes and
improvements). 

>virtual memory system (allegedly a 'new' implementation, but smelling
>strongly of Sun),

Yes, it's based on the SunOS 4.0 VM implementation, with some additional
stuff.

>the communications & terminal handling,

It's now (finally) streams based (based on the SunOS 4.0 "ldterm" "line
discipline" module, with some additional...).

>The standard directory structure is also changed (to be more Sun-like,
>I'm told).

Yes (and future-Berkeley-release-like, I think); the intent was to more
carefully segregate files that would generally be shared between
machines and those that would be specific to machines.

>For example, are the kernel source files based on BSD,
>Sun, AT&T, or what?

All of the above.

Yes, it'll be work to merge changes to R3-based systems into R4, but I
suspect it was work to merge changes to R2-based systems into R3.  The
same is true of just about any OS out there, I suspect, or at least OSes
of sizes >= that of UNIX....

Note, though, that if a lot of the changes in question involved adding
BSD features, you won't have to do much, if anything, with them in R4.