| X |
Xenix (outdated)
was a drevivative of UNIX by Microsoft. ( UNIX Ver. 7 for 16-Bit-Mikros,
later MS- SCO )
Xenix was Unix -- or at least one flavor of it. In
the late 70's,
Microsoft licensed the Unix sources from AT&T
and ported them to
a number of platforms. In those days,
AT&T would license the Unix
software but not the Unix name, thus
each company had to invent
their own name. Microsoft picked
Xenix. Microsoft did not sell
Xenix to end users. Instead,
they licensed the software to OEMs
(Intel, Tandy, Altos, SCO, etc.) who
provided a finished end-user
package. Microsoft no longer
supports Xenix, and in fact never
even offered a 286 or 386 version.
Several Unix
implementations for the PC architecture have been
tried with varying levels of
success. SCO Xenix for the PC/XT
was one. Nearly all of the PC/XT
implementations were clunkers,
because the machine lacked the
hardware necessary for robust Unix
operations. The PC/AT offered
hardware memory protection, and
SCO Xenix/286 took advantage of
it. SCO Xenix/386 added demand
paged virtual memory. These
added features made multiuser PCs
viable, and SCO Xenix popular.
SCO Xenix starts with
a Unix System III base, throws in several
Berkeley enhancements, and adds
features to obtain conformance to
the System V Interface Definition
(SVID). Today, the bulk of the
code is from System V. Xenix/386
even has capabilities to execute
Unix programs. It differs,
however, in many of the SVID `optional'
areas people tend to expect of a full
System V. SCO Xenix lacks
a real `inittab', for example.
You need to go to a real System V,
such as SCO Unix, for all these
features.
x-kernel (University
of Arizona)
The x-kernel is an object-based framework for
implementing network protocols. It defines an interface
that protocols use to invoke operations on one another
(i.e., to send a message to and receive a message from an
adjacent protocol) and a collection of libraries for
manipulating messages, participant addresses, events,
associative memory tables (maps), threads, and so on.
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