in the vintage PC community December
is DOScember, a month dedicated to videos
about Microsoft's Disk Operating System
better known as MS-DOS and the various
other versions and clones of it such as
IBM's PC DOS and Digital Research's DR DOS
there are many DOS related things I
could do videos about but I wanted to
document a little-known version of
Microsoft's
DOS that never came to be but which
could have changed the history of
computing forver
well maybe not but you can't
really find any reference to this online
so I thought I'd dig up what I can find
about it
and share it with you to begin with we
have to go all the way back to the
January 1982
issue of Byte magazine and keep in mind
this would have been
written in late 1981 when the IBM PC was
just a few months old
and their editorial of that issue was
written about the operating systems that
were written
and being planned for the IBM PC
here they wrote IBM has decided to let
the marketplace determine which of its
three operating systems will become
dominant
if any thus you can get UCSD Pascal
CP/M-86 or the IBM
Personal Computer operating system from
Microsoft but they are excited about
Microsoft's approach to the IBM PC
and they mentioned Microsoft had then
recently introduced
XENIX its superset of UNIX which today
has formed the basis of both
Linux and Mac OS but back in late 1981
when this was written
XENIX was at the top of a pyramid of
upward compatible
operating systems to be made available
by Microsoft
at the bottom is the IBM DOS called
MS-DOS by Microsoft
in the middle will be XEDOS a new
operating system written in the C
language for the 68000, Z8000
8086, and LSI-11 processors
XEDOS will contain XENIX-like features
and will be essentially a single user
version of XENIX
so that was Microsoft's original plan
for the IBM PC
you would start out with MS-DOS or
IBM DOS
and if your needs grew for larger
capacities and capabilities
you would upgrade to XEDOS and then
eventually if you needed a really
powerful computer system
you would step up to XENIX which was
their version of UNIX
but aside from that one editorial in
Byte magazine
in January 1982 I can't really find
any other information about XEDOS
although in the discussion on
Quora entitled if Bill Gates had chosen
UNIX
as the base on which to develop the
Windows operating system would Windows
still be the dominant operating system
today
Mark McCartin-Lim, computer science
professor at Wabash College
said that Microsoft had at some point
intended to migrate DOS users
over to XENIX through a single user
variant of XENIX called
XEDOS which essentially was the idea of
Linux
long before Linux existed oh I don't
think Linus Torvalds and
Richard Stallman
are gonna be happy about that saying
that Microsoft came up with the idea of
Linux before they did
so you may think XEDOS is just a long
lost
idea of Microsoft that never got off the
ground and never got released
and has pretty much been forgotten today
but actually it did get released
they just didn't call it XEDOS instead
they called it
MS-DOS 2.0 in this article in the
November 1983 issue of Byte magazine
the headline was MS-DOS 2.0 an
enhanced 16-bit operating system
features such as installable device
drivers and
XENIX compatibility have improved this
popular
operating system and they said it
represents a significant
advance and personal computer operating
systems and here's an ad which
explains it a lot more succinctly says
the UNIX connection
XENIX is the multi-user multitasking
UNIX-derived
operating system for 16-bit
microcomputers
MS-DOS 2.0 is Microsoft's single-user OS
MS-DOS and XENIX share hierarchical
file structure and I/O redirection
including
simple piping MS-DOS 2.0 also
provides XENIX compatible system calls
that means there's a migration path for
programs written to run under MS-DOS
and XENIX what's more both MS-DOS and
XENIX are supported by
Microsoft languages that's your single
supplier advantage from Microsoft
Microsoft may have also decided to
abandon the XEDOS
name because of potential confusion with
Zenith's version of
MS-DOS which in American English is also
pronounced Z-DOS
so here I am at the MS-DOS 2.11
prompt this is the Tandy 1000 version
but that doesn't make any difference
and I'll show you some of the XENIX or
UNIX-like features that would have been
in
XEDOS but instead got integrated into
DOS 2.0 first and foremost is the
introduction of subdirectories
with the MKDIR or better known as just
MD
command to make a directory so make a
directory called
test
now I can change that directory
and now we're in the test directory
interestingly it printed it in lower
case and another capability
borrowed from UNIX and XENIX
is piping for example I have a BASIC
program I want to
display on the screen
but once I get past the first
screenful it scrolls by too
quickly to read so the way you can pause
it after
every screenful to let you read it is to
TYPE
the file and then pipe it into the MORE
command
and you can see now once it fills up the
screen it shows
--More-- at the bottom and you can press
any key
and it'll fill up the next screen and so
on and so forth
and the next feature that was borrowed
from UNIX
and which would have been in XEDOS is
redirection so for example you have this
directory listing here and you want to
save it into a file
and the way you do that is you type the
command and then the greater-than symbol
and then the file name you want to
redirect the output of the command
into so I'll call it DIRLIST.TXT
and that redirects the output of
directory into that text file so then we
can
edit it or print it and it can redirect
the other way too
with the less-than symbol for example I
created a text file called
TIME.TXT and it contains a specific
time I typed in of 20 o'clock
or 8 p.m. and I can redirect that
into the TIME command so if you had some
crazy idea to always set the time
to 8 o'clock p.m. you could redirect
the contents of this TIME.TXT file
into the TIME command
and it'll automatically enter a time
of
20 o'clock and that's a pretty stupid
example but it's the only one I could
think of
off of the top of my head so that's all
pretty rudimentary stuff
anybody who has learned DOS in the past
35 years
is familiar with those concepts but
there were actually some hidden commands
and DOS 2.0 that were designed to make
it more
XENIX-like to make it more like what
would have been
XEDOS but were never documented
and were discontinued from DOS 3.0 and
later versions
these are two CONFIG.SYS commands called
AVAILDEV
and SWITCHAR and you can see I just
created a CONFIG.SYS
file containing the commands
AVAILDEV=FALSE
and SWITCHAR=- (dash
or hyphen) so we'll restart
MS-DOS and we'll see what difference
that makes
so at first everything looks normal but
let's type a command for example
DIR /W
and what happened it says file not found
that's because with that SWITCHAR
command I changed the switch
character from the slash to the dash
or hyphen which is what UNIX and XENIX
uses
so now instead of DIR /W I have to
type DIR -W
and now it works as intended
and notice something else where it says
Directory of A:
instead of a backslash it uses a regular
slash
that's because since the slash character
is no longer needed for the switch
character since I changed it
it's now used for directories just like
UNIX or XENIX
so for example I can make a directory
called TEST
and to change into that directory I type
CD
slash TEST instead of backslash
and now we're in the TEST directory
and to go back to the root directory
instead of CD backslash you type
CD slash and now I changed the prompt
into
what would be more normal for later
versions of DOS
and notice instead of A:
backslash it says a A: slash
so this is a feature undocumented in
MS-DOS 2 intended to make it more UNIX-like
which was removed from later versions of
MS-DOS
because they never documented it for
some reason they never wanted it to be
used
even though they designed it into the
product and this is all
part of what would have been XEDOS but
instead got integrated
into MS-DOS and remember that command I
added to
CONFIG.SYS called AVAILDEV equals
false that changes the way devices are
addressed to make it more UNIX-like
and you can see on the directory there
there's some file names that normally
would not be possible to create
such as NUL and COM1 normally those are
reserved
device names so you normally cannot
create files using those names
but since I added this command to
CONFIG.SYS
now the way devices are addressed is
more like UNIX
so for example you know the COPY CON
command which allows you to type
text directly into the keyboard and save
it into a file
from the DOS prompt but now with this
command
in effect the way the device is
addressed
is to type slash DEV
slash CON
and then type in your file name
and now we can type whatever we want
and it'll save the file
now I deleted that CONFIG.SYS file those
AVAILDEV and SWITCHAR commands in it
and I'll restart and now things
should be back to normal DIR /W
should work like normal now
and yes it does and also notice the
directory
is backslash instead of slash and if
I try to create a file
called LPT1 it's not going to work it's
actually redirecting
it to the printer like it's supposed to
instead of creating a file called
LPT1 so that's just the quick history of
XEDOS the planned operating system from
Microsoft that would have been a
stepping stone
between MS-DOS and XENIX or UNIX
but never came to be because instead its
best ideas got
integrated into MS-DOS 2.0
and left some odd quirks along the way
which were never officially documented
but what you can use to make
MS-DOS work more like XENIX or UNIX or
what today you would call Linux
Bill Gates: "This new generation
will enable a whole new set of
applications
in fact there'll be hundreds and
hundreds of great applications
that take PCs much further than they've
gone before
and allow us to move towards this
exciting vision
of a machine on every desktop"