28 Jun
2011
28 Jun
'11
7 a.m.
my two cents:
- system unity - the system was designed from the ground up,
including design tools such as assembler and language
and compiler, by a small group of people. This allowed
the designers to get great unity.
- Utility - the designers used the system, and made sure the system
they built was useful for them. This ensured that it was also useful
for other people like them, and it turns out for lots of other people
less like them, too.
- simplicity - perhaps a result of the small team of people, the system
was understandable. The designers sometimes chose simplicity over
generality or even elegance (ie. EAGAIN, making callers job harder, but
simplifying kernel). I think there's a great deal of pragmatism here that
worked well with the unity. They knew the whole system and were able
to see where to give a little and where to take a little.
- Open design - the fact that unix came with readable and understandable
documentation and source code helped it immensely! Users were free
to take the system, study it, change it and tailor it to their needs. Others
were able to imitate and extend (for better or worse).
and like any popular system, a dash of good luck.
Tim
On Mon, Jun 27, 2011 at 2:11 PM, Warren Toomey <wkt(a)tuhs.org> wrote:
All, IEEE Spectrum have asked me to write a paper on
Unix to celebrate the
40th anniversary of the release of 1st Edition in November 1971. I'm after
ideas & suggestions!
I think my general thrust is that Unix is an elegant design, and the
design elements are still relevant today. The implementation is mostly
irrelevant (consider how much the code has changed from assembly -> C,
from the simple data structures in V7 through to current BSD), but the
original API is classic. Note that about 28 of the 1st Ed syscalls are
retained in current BSDs and Linux, and with the same syscall numbers.
I'm having some trouble thinking of the right way to explain what is
an elegant design at the OS/syscall level, so any inspirations/ideas
would be most welcome. I might highlight a couple of syscall groups:
open/close/read/write, and fork/exec/exit/wait.
If you have any references/URLs you think I should look at, please
pass them on to me.
I'm also trying to chase down some quotes; my memory seems to be failing me
but I'm sure I've seen these somewhere:
- in a paper, I think by Thompson & Ritchie, where they assert that the
kernel should provide no more than the most minimal services to the
userland programs. I thought this was the CACM paper, but I can't spot
this bit. Maybe it's in Thompson's preface to the Lions Commentary,
of which my copy is elsewere at present.
- I'm sure I remember someome (Kernighan?) say that Ritchie encouraged
them to espouse the use of processes as context switching was cheap,
but later measurements showed that in fact it wasn't that cheap in
the early versions of Unix.
Anyway, if you can think of good ideas/references about the elegance of
Unix, especially from the design perspective, I would much appreciate them.
Cheers,
Warren
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Tim Newsham | www.thenewsh.com/~newsham | thenewsh.blogspot.com