Week 10:

                       --  ShagOS  --

           Host: Frank Barrus, (Xerox, and RIT Student)

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	Attendance is free of charge and is open to the public
		Refreshments will be served.
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Abstract:

    ShagOS was originally developed in 1992 as an independent
study project to write a portable object-oriented microkernel-based
operating system with dynamically loadable device drivers.  It was
written mostly in C, with very little machine-dependent code, and
could run on the VAX and Intel architectures.  It had only three
system calls- two to convert between string identifiers and 
internal label codes, and one to invoke a method call on an
object.

    ShagOS today has been completely redesigned and rewritten (many times)
in C++, and is an ongoing experiment with using an object-oriented
paradigm as the framework for a full operating system, with distributed
computing being a prime consideration of most design decisions.

    Everything in ShagOS is handled as an object, with an attempt
to use simple methods for as many objects as possible to keep
their interfaces consistent.  Thus, filesystem-style operations
(for reading, writing, and getting and setting member attributes) can 
be applied to most objects, and the shell provides a Unix-style
interface for traversing the object hierarchy, even allowing
the user to change the current directory to be inside a device,
to look at characteristics of that device as simply as listing files.

    Objects are created with a dialect of C++, with dynamic extensions,
which is processed through DECO (Dynamic Encapsulator of C++ Objects)
to generate the run-time tables needed for handling all dynamic
object interaction.  Objects support adding forwarders and superclass
objects at runtime, and have interfaces that are independent 
of their implementation.

    This seminar will cover the internal structure of both the old
and new ShagOS, the SOLO boot loader, the object management and
communication system, and the DECO syntax extensions.  If there
is enough time, demonstrations of old and new ShagOS will also
be presented.  Comments, questions, and suggestions will 
be greatly encouraged throughout the seminar.

    Slides for this seminar should be available sometime next week
from "http://www.csh.rit.edu/~shaggy".  The old ShagOS source code,
along with the SOLO boot loader, are available now from
"http://www.csh.rit.edu/~shaggy/software.html".
The source code to the new ShagOS, along with DECO, will also
be available there in a few months.