From: norman@oclsc.org (Norman Wilson)
To: tuhs@tuhs.org
Subject: [TUHS] Groups origins
Date: Sun, 3 Oct 2021 21:22:20 -0400 (EDT) [thread overview]
Message-ID: <20211004012220.C3404640CC6@lignose.oclsc.org> (raw)
Groups appeared surprisingly late (given how familiar
they seem now): they don't show up in the manual
until the Sixth Edition.
Mea culpa; read too hastily. The change actually
came with the Fourth Edition, at the same time as
several other landmark system changes:
-- Time changing from a 32-bit count of 60Hz clock
ticks (which ran out so quickly that its epoch kept
moving) to the modern 32 bits of whole seconds, based
at 1970-01-01T00:00:00 GMT (which takes much longer
to run out, though the horizon is now visible).
-- The modern super-block. In 4/e, the super-block
began at block 0, not 1 (so bootstrapping was rather
more complicated); the free list was a bitmap rather
than the later list of blocks containing lists of
free block numbers.
-- The super-block contained a bitmap of free
i-numbers too. All told, the free block and free
i-node map made up a 1024-byte super-block.
-- I-numbers 1-40 were device files; the root
directory was i-number 41. The only file-type
indication in the mode word was a single bit to
denote directory.
It was already clear that the lifetime of the
bitmaps was running out: the BUGS section says
two blocks isn't enough for the bitmaps for a
20-megabyte RP02.
Norman Wilson
Toronto ON
next reply other threads:[~2021-10-04 1:24 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-04 1:22 Norman Wilson [this message]
-- strict thread matches above, loose matches on Subject: below --
2021-10-03 22:10 Norman Wilson
2021-10-04 13:39 ` John P. Linderman
2021-10-03 21:54 Will Senn
2021-10-03 23:22 ` Warner Losh
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