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From: pardo@june.cs.washington.edu (David Keppel)
Newsgroups: comp.os.research
Subject: Kernel Taxonomy
Message-ID: <14956@darkstar.ucsc.edu>
Date: 23 Apr 91 18:21:24 GMT
Sender: usenet@darkstar.ucsc.edu
Organization: Computer Science & Engineering, U. of Washington, Seattle
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Approved: comp-os-research@jupiter.ucsc.edu

There are at least three kinds of OS kernels: monolithic, modular,
and kernelized.  I would like comments (e-mail, I'll summarize) on
what's missing, wrong, or "right but not the only way to see it"
with the following definitions:

* Monolithic

  Traditional: everything runs in one address space, the only
  official interface to the kernel is e.g., the published set
  of system calls.

* Modular

  The official kernel interface specification may also include
  internal components along module boundaries.  These internal
  components are not visible to user-level processes, they are
  for e.g., kernel extesibility.

  (The word `modular' is a misnomer and I'll gratefully accept
  alternatives  That is, a monolithic kernel may be built using
  good, modular, structured programming techniques without
  exporting the particular interfaces.  A ``modular'' kernel
  exports those interfaces and they don't change between
  releases of the OS.)

* Kernelized (or micro-kernel)

  An OS that is both modular and has modules broken in to
  multiple address spaces.

Comments?

	;-D on  ( Pay no kernel tax on'a me! )  Pardo