Editing Coherent (operating system)

{{Short description|Unix operating system clone}}
{{Lead too short|date=February 2023}}
{{Infobox OS
| name                   = Coherent
| logo                   = Coherent.png
| logo size              = x64px
| screenshot             = Coherent 4.2.10 installer screenshot.png
| caption                = Coherent 4.2.10 installer
| developer              = [[Mark Williams Company]]
| source_model           = Closed source; [[open source software|open sourced]] in 2015
| kernel_type            = [[Monolithic kernel|Monolithic]]
| supported_platforms    = [[PDP-11]], [[x86]] ([[Intel 8088|8088]], [[Intel 80286|286]], [[i386|386]], [[i486|486]]), [[Motorola 68000]], [[Zilog Z8000]]
| ui                     = [[Command-line interface|Command-line]] ([[KornShell]])
| family                 = [[Unix-like]]
| released               = {{Start date and age|1980}}
| latest_release_version = 4.2.14
| latest_release_date    = {{Start date and age|1994}}
| latest_test_version    =
| latest_test_date       =
| marketing_target       =
| programmed_in          =
| prog_language          = [[C (programming language)|C]]
| language               = [[English language|English]]
| updatemodel            =
| package_manager        =
| working_state          = Discontinued
| license                = 2015: [[BSD licenses|BSD-3-Clause]]<ref name="license-2015">{{cite web|title=Mark Williams Company Sources|url=http://www.nesssoftware.com/home/mwc/source.php|access-date=2021-06-18|archive-date=2015-01-06|archive-url=https://web.archive.org/web/20150106055814/http://www.nesssoftware.com/home/mwc/source.php|url-status=live}}</ref><br />Original: Proprietary
| website                =
}}
[[File:Coherent 4.2.10 i386 Boot.png|thumb|Coherent system startup and login prompt]]
[[File:Coherent 4.2.10 i386 Root Directory.png|thumb|Viewing the [[root directory]] and system information]]

'''Coherent''' is a clone of the [[Unix]] [[operating system]] for [[IBM PC compatible]]s and other [[microcomputer]]s, developed and sold by the now-defunct [[Mark Williams Company]] (MWC). Historically, the operating system was a proprietary product, but it became [[Open-source software|open source]] in 2015, released under the [[BSD licenses|BSD-3-Clause]] license.<ref name="license-2015" />

==Development==
Coherent was not Unix; the Mark Williams Company had no rights to either the Unix [[trademark]] or the [[AT&T Corporation|AT&T]]/[[Bell Labs]] [[source code]]. In the early years of its existence, MWC received a visit from an AT&T delegation looking to determine whether MWC was infringing on AT&T Unix property. The delegation included [[Dennis Ritchie]], who concluded that "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." However, he also stated that:<ref>{{Cite newsgroup
|title=Re: Coherent
|author=Dennis Ritchie
|date=April 10, 1998
|newsgroup=alt.folklore.computers
|message-id=352DC4B7.3030@bell-labs.com
|url=https://groups.google.com/group/alt.folklore.computers/msg/8477ba2953351ee4
}}</ref>

{{quote|[...] looking at various corners [for peculiarities, bugs, etc. that I knew about in the Unix distributions of the time] I couldn't find anything that was copied. It might have been that some parts were written with [AT&T] source nearby, but at least the effort had been made to rewrite. If it came to it, I could never honestly testify [...] that what they generated was irreproducible from the manual.}}

Much of the operating system was written by alumni from the [[University of Waterloo]]: [[Tom Duff]], Dave Conroy, Randall Howard, Johann George, and Trevor John Thompson. Significant contributions were also made by people such as Nigel Bree (from [[Auckland, New Zealand]]), the later author of [[Ghost (disk utility)|Ghost]].<ref>{{Cite web|url = http://www.nesssoftware.com/home/mwc/manual.php|title = Preface|date = 1994|website = COHERENT manual|publisher = Mark Williams Company}}</ref>

==Versions==
Coherent was originally written for the [[PDP-11]] range of minicomputers in 1980,{{r|berg198506}} then ported to various early 1980s [[microcomputer]] systems including [[IBM PC compatible]]s and machines based on the [[Zilog Z8000]] and [[Motorola 68000]]. Initially sold to [[OEM]]s, starting 1983 it was available on the consumer market from MWC directly. At this point, Coherent 2.3 offered roughly the functionality of [[Version 7 Unix]] on PC hardware, including the [[nroff]] formatter but not the [[Berkeley Software Distribution|BSD]] extensions offered by competing Unix/clone vendors; compared to its competitors, it was a small system distributed on only seven [[double-sided disk|double-sided]] [[floppy disk]]s, costing only [[United States dollar|US$]]500 for a license.<ref name="pcmag">{{cite news |newspaper=PC Mag |last=Hannotte |first=Dean |date=12 June 1984 |title=A Good Buy on UNIX |url=https://books.google.com/books?id=amQldGdl9LkC&pg=RA1-PA250 |pages=250–254}}</ref>{{r|berg198506}}

Coherent runs on most [[Intel]]-based PCs with [[Intel 8088]], [[Intel 80286|286]], [[i386|386]], and [[Intel 80486|486]] [[Microprocessor|processors]]. Coherent version 3 for Intel-based PCs requires at least a 286; Coherent version 4 for Intel-based PCs requires at least a 386. Like a true Unix, Coherent is able to [[computer multitasking|multitask]] and support [[Multi-user software|multiple users]]. From version 4, released 1992,<ref>{{cite news |newspaper=Computerworld |date=8 June 1992 |title=In brief |page=51 |url=https://books.google.com/books?id=JpZFcozwnrkC&pg=PA51}}</ref> Coherent also has support for [[X Window System|X11]] and [[ManaGeR|MGR]] [[windowing system]]s.{{Citation needed|date=February 2015}}

Later versions of Coherent (version 4 and higher) support features common in modern Unix-like systems, including a version of [[MicroEMACS]], access to [[FAT16]] [[file system]]s,{{Citation needed|date=February 2015}} an [[Program optimization|optimizing]]{{Citation needed|date=February 2015}} [[C (programming language)|C]] [[compiler]], and a modified version of Taylor [[UUCP]].{{Citation needed|date=February 2015}} The final releases of Coherent also fully support the [[Intel Binary Compatibility Standard|iBCS]] [[COFF]] binary standard,{{Citation needed|date=February 2015}} which allow binary compatibility with [[SCO OpenServer|SCO Unix]] applications, including [[WordPerfect]], [[Lotus 1-2-3]], and several [[Microsoft]] applications including [[QuickBASIC]], [[Microsoft Word]], and [[MultiPlan]]. The last 386 versions supported [[virtual memory]], but not [[demand paging]].

A [[Zilog Z8000]] port of Coherent was also used by the canceled [[Commodore 900]] system.<ref>{{Cite news |newspaper=InfoWorld |date=6 April 1984 |title=From the news desk |page=9 |url=https://books.google.com/books?id=iC4EAAAAMBAJ&pg=PA9}}</ref>

In 1983, NCSC (a subsidiary of [[Nixdorf Computer|Nixdorf]]) announced a port of Coherent to IBM mainframes, in the form of a Unix compatibility subsystem for IBM's [[DOS/VS]] and [[DOS/VSE]] and Nixdorf's [[Edos/VS]] and [[Edos/VSE]] operating systems, known as Programmer Work Station/VSE-Advanced Functions, or PWS/VSE-AF for short.<ref>{{citation|title=Nixdorf unwraps Unix-compatible T/S for IBM|url=https://books.google.com/books?id=_itgx7IkelMC&pg=PA4|volume=27|date=12 September 1983|publisher=IDG Enterprise|page=4|issn=0010-4841|work=Computerworld|issue=37}}</ref>

The Mark Williams Company closed in 1995.<ref>[https://groups.google.com/group/comp.os.coherent/msg/e36245dd33a5fbd7 Closing Announcement]</ref>

On January 3, 2015, Coherent sources were released under the [[BSD licenses|BSD-3-Clause]] license.<ref name="license-2015" />

[[File:Coherent1.jpg|thumb]]

==Reception==
''BYTE'' in 1984 called Coherent a "highly compatible UNIX Version 7 lookalike".<ref name="phraner1984fall">{{Cite magazine |url=https://archive.org/stream/byte-magazine-1984-09/1984_09_BYTE_09-09_Guide_to_the_IBM_PCs#page/n61/mode/2up |title=The Future of Unix on the IBM PC |last=Phraner |first=Ralph A. |date=Fall 1984 |magazine=BYTE |pages=59–64}}</ref> In 1985 it criticized the difficulty of installation, but stated that "as a UNIX clone, Coherent is amazingly complete ... it should be easy to port programs ... the price of $495 is a bargain".<ref name="rochkind1985fall">{{cite news | url=https://archive.org/stream/byte-magazine-1985-11/1985_11_BYTE_10-11_Inside_the_IBM_PCs#page/n233/mode/2up | title=Pick, Coherent, and THEOS | work=BYTE | date=Fall 1985 | access-date=19 March 2016 | author=Rochkind, Marc J. | pages=231}}</ref>

Coherent "is not without drawbacks", ''[[UnixWorld]]'' in 1985 said, but favorably cited its low hardware requirement, "only $500" cost, and clear documentation. The magazine found that Coherent was "surprisingly complete for a rewrite", with good interactive and multiuser performance, and estimated that up to eight tasks could be run while remaining usable. While noting the inability to run the [[AIM Multiuser Benchmark]], and lack of certain utilities such as [[csh]] and [[Source Code Control System|SCCS]], ''UnixWorld'' concluded that "Coherent is still a good choice for the IBM PC/XT owner who wants a Unix-compatible operating system at a very reasonable cost and low system hardware overhead".<ref name="berg198506">{{Cite magazine |last=Berg |first=Ronald |date=June 1985 |title=Coherent on the IBM PC |url=https://archive.org/details/Unix_World_Vol02_05.pdf/page/n67/mode/2up?view=theater |access-date=2025-05-17 |magazine=Unix World |pages=66-70}}</ref>

Early 1990s reviews of Coherent pointed out that the system was much smaller than other contemporary Unix offerings, as well as less expensive at US$99.95, but lacking in functionality{{r|kaare}} and software support.<ref>{{cite news |first=Patrick |last=Dryden |date=23 April 1990 |title=PC Users Get Alternative to Unix |newspaper=InfoWorld |page=40 |url=https://books.google.com/books?id=LTsEAAAAMBAJ&pg=PA40}}</ref> ''PC Magazine'' called Coherent 3.0 a "time capsule" that captured the state of Unix in the late 1970s, without support for [[computer mouse|mice]], [[Local area network|LANs]] or [[SCSI]] disks, good for learning basic Unix programming but not for business automation.<ref name="kaare">{{cite news | url=https://books.google.com/books?id=JZxkO0PpksUC&pg=PT61 | title=Coherent: Unix power for $99 | work=PC Magazine | date=11 December 1990 | last=Christian | first=Kaare | page=50}}</ref> A review in the [[AUUG]]'s newsletter was more positive, favorably comparing Coherent to [[MKS Toolkit]], [[Minix]] and [[Xenix]], and suggesting it might fill a niche as a low-end training platform.<ref>{{cite journal |title=Good Things Still Come in Small Packages |first=Jack |last=Dikian |year=1991 |journal=Australian UNIX Systems User Group Newsletter |volume=12 |issue=1 |pages=21–22 |url=https://books.google.com/books?id=KKHZnUYF7UIC&pg=PA21}}</ref>

==See also==
* [[PC/IX]]
* [[Venix]]

== References ==
{{Reflist}}

==External links==
{{Commons category|Coherent}}
*[http://www.landibase.com/coherent.html Andrzej Popielewicz's GNU stuff for Coherent website]
*[http://neil.franklin.ch/Usenet/alt.folklore.computers/20001107_Coherent Coherent history archive]
*[http://www.tuhs.org/Archive/Distributions/Other/Coherent/ Installation Media for Coherent 4.2.10]
*[http://thebeezspeaks.blogspot.fr/2012/05/my-life-with-coherent-part-2.html Coherent image for qemu]
*[http://www.nesssoftware.com/home/mwc/source.php Mark Williams Company Sources]
*[https://www.icl1900.co.uk/unix4fun/coherent/index.html Virtualbox, Qemu and PCem VM's with Coherent 3.x, 4.0, 4.2.x, DDK, X11, sources...]

{{Unix-like}}

{{DEFAULTSORT:Coherent (Operating System)}}
[[Category:Discontinued operating systems]]
[[Category:Formerly proprietary software]]
[[Category:Lightweight Unix-like systems]]
[[Category:Software using the BSD license]]
[[Category:Unix variants]]
[[Category:X86 operating systems]]