From: Robert S. Thau (rst@ai.mit.edu)
Date: Tue Jan 02 2001 - 15:04:59 PST
Tony Finch writes:
> I would recommend the Lions book at first, because it's a brilliant
> illustration of how simple an effective OS can be. Modern OSs are too
> big to be understood that easily. The fact that 6th Edition Unix is a
> historical artifact can be seen as either an advantage or a
> disadvantage :-) (But at least now you can get it for free to run on
> your 11/70 emulator.)
The Lions book is the best thing going for showing how a piece of
small, well constructed code can do a complicated job. No question.
But in order to appreciate it, you need to understand the job that the
code is doing, at the level of the Unix (v6) system-call API and (at
least very roughly) the underlying hardware --- if you've just never
been told, for instance, that the same numerical memory address refers
to different words of memory depending on the state of the processor,
or why, then the considerable body of code in Unix v6 which manages
those translations will be completely obscure, and Lions won't help
much because he assumes you already know.
(I'm not saying you have to understand, say, 'estabur' --- the routine
which sets up, in effect, the virtual-to-physical mappings for a
userland process --- in detail in order to get anything out of the
Lions book. You can treat the guts of that routine as a black box,
and still get a lot out of it. But you do need to understand roughly
what it does, and why it is invoked).
Which is why I suggested Bentley's Programming Pearls, or something
like, as a gentler introduction for the true novice.
rst
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