Shared Memory in BSD4.3 is lacking?

[Kenneth Almquist]

In article <7371 at brl-smoke.ARPA>, gwyn at brl-smoke.ARPA (Doug Gwyn ) writes:
> In article <7435 at ncoast.UUCP> allbery at ncoast.UUCP (Brandon Allbery) writes:
>> Umm, as far as I know, USG 3.0 (== System III) did NOT have shared memory.
> 
> Right -- it appeared (along with semaphore and message IPC) in USG 4.0,
> which seems to have merged these in from earlier UNIX/RT as part of the
> consolidation of internal AT&T UNIX variants.

Not quite.  USG has a decent release numbering scheme until the marketing
folks messed it up.  Once per year, a new release of UNIX would be issued
and the first digit of the release would be updated, giving us releases
with numbers like 3.0, 4.0, and 5.0.  Additional releases were made in
the middle of the UNIX year for the benefit of people who wanted new
features before the next major release; these were given numbers like
5.1, 5.2, 5.3, and 5.4.  A third digit was used for bug fixes, so in
parallel with the development of 5.1 through 5.4 we also had releases
5.0.1, 5.0.2, 5.0.3, etc.  Occasionally, bug fixes were also issued for
intermediate releases; I seem to recall there was a release 4.2.1, for
example.

System III == USG release 3.0.1 and System V == USG release 5.0.1.  Shared
memory first appeared in USG release 4.2.  Since 5.0 was the first major
release containing shared memory and since System V is almost the same
as release 5.0, it seems reasonable to talk about shared memory as a
system V feature.

UNIX/RT also had shared memory, semaphores, and messages, but the system
call interface to these features was quite different (no access control,
messages were sent to processes rather than to message queues, semaphore
operations were limited to P and V, etc.)
				Kenneth Almquist
				ka at june.cs.washington.edu