The COHERENT Operating System

The Mark Williams Company
And the COHERENT operating system
=================================
Feb 17, 2024

William Mark Schwartz was a chemist living in Chicago and running a
chemical company called the Mark Williams Chemical Company. Some of
his employees complained of issues like fatigue, headaches, and
indigestion which prompted him to create a beverage that would solve
these issues. These complaints were more of the "man, I am tired"
variety and not that Schwartz was working them to death. This
beverage was Dr. Enuf, likely developed in 1949, for which Schwartz
applied for a trademark on the 19th of May in 1951. The trademark was
granted on the 2nd of December in 1952, and the beverage was first
sold commercially on the 4th of April in 1951. The company produced
paints and other products as well (being a chemical company), but Dr.
Enuf is the most famous. The rights to the formula for Dr. Enuf were
eventually bought by Charles Gordon of Tri-City Beverage in Johnson
City, Tennessee.

William Mark Schwartz's son, Robert Schwartz, didn't wish to follow
his father into chemistry. He was a software developer, and he wanted
to move the company into that field. Specifically, Robert Schwartz
saw the introduction of the microprocessor and early microcomputers
as having extreme potential. This transition occurred in 1977 and the
"Chemical" was dropped from the name, and the new Mark Williams
Company was headquartered in Northbrook, Illinois.

Logo of the Mark WIlliams Company
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Stephen A. Ness joined the computer science department of Stanford
University as a graduate student in the autumn of 1968.
Unfortunately, his interested began to fade, so he spent quite a bit
of time going to movies. He started working at the Festival Cinema in
Palo Alto sweeping floors, cleaning bathrooms, and running the
projectors. He was a movie buff and this worked for him for some
time. As his interest in working at the theater was beginning to
wane, he began to long for a job in software development. In early
February of 1977, Donald Knuth paid a visit to the theater and asked
Ness what he was up to, Ness told him about his job search. The next
day, Knuth got a call from Schwartz. Schwartz was searching for a
programmer and Knuth provided Schwartz with Ness's number.

The start of the microcomputer world was dominated by BASIC. More
particularly, it was dominated by Microsoft BASIC, and Schwartz
wanted to compete. Ness told Schwartz that he could build a BASIC
interpreter in about four months, which was just a guess on Ness's
part. He hated BASIC, but he was familiar enough with it, and he
really wanted the job. On top of that, Schwartz was letting him work
from home. With both parties satisfied, work began. Of course, this
"working from home" was complicated. Disk drives of any kind were
expensive and difficult to come by, so Ness commuted from Palo Alto
to Pacific Grove where he used Gary Kildall's computers until he
purchased his own machine and disk drive later in the year. The BASIC
that Ness built for the Mark Williams Company was XYBASIC.

The XYBASIC manual cover, from Stephen Ness via nesssoftware.com
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Getting a start early on in the computer revolution with a BASIC was
a good idea. BASIC was everywhere, and it was a product that would
sell. Revenues from XYBASIC allowed the company to expand into
operating systems. MWC purchased a PDP-11 in the late 1970s and began
working on a UNIX clone. This would allow them, just as XYBASIC did,
to offer a stellar product at a price far lower than any of the
competition. COHERENT was first sold through OEMs for PDP-11
minicomputers in 1980. However, it was quickly ported to the Zilog
Z8000, the Motorola 68000, and the 8086. It was offered at retail to
owners of machines utilizing these CPUs in the spring of 1983. One
OEM who picked up COHERENT was Commodore.

Announcment in BYTE, February 1984
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Announcement in BYTE, June 1984
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The workstation Commodore was building was the C900. This system
offered a 1024x800 display on a screen of either fourteen or twenty
inches, a 20MB HDD, a 1.2MB five and quarter inch floppy disk drive,
two RS232 ports, a Centronics port, an IEEE-488 port, 512K RAM, and
the COHERENT operating system version 2.3 with both BASIC and C. The
C900 could be expanded with hard disk upgrades up to 67MB, memory up
to 2MB, and RS232 port count up to eight (for a total of eight
terminals for concurrent multi-user support). On the software side,
add-ons included: Pascal, COBOL, plotting software, and graphical
terminal support. The C900 was built in Germany with a US release
scheduled for the third quarter of 1985. Pricing started around $2700
(about $7740 in 2024).

Commodore 900, image from vintagecomputer.ca
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Unfortunately, the C900 project was canceled with very few units
having made it to market. Commodore's focus shifted to Amiga, and
their UNIX workstation aspirations disappeared.

Thankfully, the IBM PC and its clones were selling well and COHERENT
was also present there for $500 (about $1433 in 2024) requiring a
minimum of an IBM PC with a hard disk. With just an IBM PC and a hard
disk, COHERENT could support three concurrent users with terminals
attached via serial ports.

Ad from BYTE, February 1984
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Given that UNIX licenses were prohibitively expensive during this
time period, COHERENT was quite a good deal. Adding that it included
both a C compiler and a BASIC compiler, COHERENT was easily the most
affordable workstation operating system and software development
suite available at the time. As for what COHERENT really offered, it
was essentially V7 UNIX complete with nroff, diff, sed, ed, awk, lex,
yacc, db, man, bc, make, the Bourne shell, and other expected
utilities. This system was packed onto seven double-sided floppy
disks, and packaged with a manual.

Of course, AT&T didn't exactly love the idea of someone offering a
UNIX-like operating system for substantially less money while also
not paying them their due. So it was that around the time that the PC
port was made, AT&T sent Dennis Ritchie went to the Mark Williams
Company offices in Northbrook to ascertain whether or not COHERENT
represented an instance of intellectual property theft. According to
Ritchie, the offices were in an industrial area and the feel of the
premises hadn't strayed far from that of a paint company. As for the
investigation of COHERENT, Mark Williams Company would not allow AT&T
to have a look at their source code, and therefore the most that
Ritchie could do was look around the system. He had notes with him
about specific things that could indicate a direct copy without much
doubt, but that was the most he could do. His conclusion is that
COHERENT was made with considerable study of AT&T UNIX, but that it
wasn't a direct copy. He stated:

It was very hard to believe that Coherent and its basic
applications were not created without considerable study of the OS
code and details of its applications. Looking at various corners
convinced me that I couldn't find anything that was copied. It
might have been that some parts were written with our source
nearby, but at least the effort had been made to rewrite. If it
came to it, I could never honestly testify that my opinion was that
what they generated was irreproducible from the manual.

Given that the making of a UNIX-like operating system required a C
compiler, the MWC C compiler was quickly ported to other systems and
offered as a standalone product starting in 1981. Porting the
compiler to MS-DOS was a given as IBM compatibles running MS-DOS
dominated the market by the middle of the 1980s and COHERENT was
offered for those machines. MWC offered their C compiler for MS-DOS
at a price of just $75 (around $254 in 2024) and an advanced
interactive debugger was offered for another $75.

1987 Byte Ad
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In early 1986, the Mark Williams company began offering their C
compiler for the Atari ST. This software package came with a rather
complete manual that covered the C compiler itself in five hundred
twelve pages, the make utility with another twenty five pages, and
Micro EMACS in another seventy seven pages. Beyond cc, make, and
emacs, the MWC C compiler for the ST shipped with a symbolic
debugger, assembler, linker, and a series of libraries that offered
sorts, enums, and a random number generator. This product sold for
$180 (about $506 in 2024). In autumn of 1987, MWC followed up with
version 2 of their C compiler for the ST. This version increased the
compiler's speed, added RAM disk support for temporary files, a shell
that implemented a small subset of UNIX commands, and improved
documentation. STart Magazine's review stated the product was without
equal.

From what I can gather, COHERENT version 1 was only available on the
PDP-11. COHERENT version 2 began shipping on OEM systems, and the
point releases of 2.3 and 2.5 were offered at retail while also
having been present on some OEM systems.

COHERENT version 3 was released in May of 1990 for $99.95 (about $235
in 2024). It required a 7MB or larger HDD, 640K RAM, a high density
disk drive, and at least an Intel 80286 CPU. Given the nature of the
286, the kernel fit in just 64K RAM with support for multitasking and
and multiple concurrent users. This was still a V7 UNIX clone and it
continued to lack BSD enhancements (like vi), though it did come with
Emacs. It also lacked the Korn shell, X, SCSI support, and MCA
support. The COHERENT manual at this point was one thousand pages.
COHERENT v3 sold around forty thousand copies between 1990 and 1992
which would have resulted in revenues around $4 million (nearly $10
million in 2024).

COHERENT version 4 was released in May of 1992 for $100 (around $219
in 2024). This version made COHERENT a fully 32 bit operating system
and required at least an Intel 80386 CPU and 1MB of RAM. This version
also brought official support for X Windows and MGR to COHERENT for
the first time. This version was roughly compatible with UNIX SVR3.

COHERENT V4.2 with X11R5 running TWM, image from Udo Monk
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COHERENT version 4.2 was released in 1994. This version brought
STREAMS, POSIX.1 and POSIX.2 compatibility to COHERENT making it
largely compatible with UNIX SVR4.

The 1990s were tough. COHERENT was always a distant second to XENIX,
but the early 1990s brought more competitors into the mix. BSD was
making its way onto X86 compatible machines with many improvements
over AT&T UNIX with a cost of zero dollars while Linux was quickly
growing and gaining market share with SLS, Slackware, and Debian, add
to both of those that the commercial UNIX workstation market in
general was losing ground to Windows NT. Likewise, the ST, where MWC
saw the most success with their programming language tools, was no
longer popular enough to provide significant revenues. These
pressures all came to a head and the Mark Williams Company closed in
1995. In 2001, Stephen Ness archived the MWC sources at the request
of Robert Schwartz, and in 2015 that source code archive was released
under a 3-clause BSD license.

<https://github.com/gspu/Coherent>

From: <https://www.abortretry.fail/p/the-mark-williams-company>