Coherent (operating system)
Encyclopedia
The Coherent operating system
was a Version 7 Unix
clone by the now-defunct Mark Williams Company
, originally produced for the PDP-11
in 1980. A port was introduced in 1983 as the first Unix-like
system for IBM PC compatible
computers
.
Coherent was able to run on most Intel-based PCs with Intel
8088
, 286
, 386
, and 486
processors
. Coherent version 3 for Intel-based PCs required at least a 286, Coherent version 4 for Intel-based PCs required at least a 386. Like a true Unix, Coherent was able to multitask
and support multiple users. From version 4 on Coherent also had support for X11
and MGR
windowing systems.
Later versions of Coherent (version 4 and higher) supported features common in modern Unix-like systems, including a version of MicroEMACS
, access to DOS
FAT16
File system
s, an optimizing
C
compiler
with linker, and a modified version of Taylor UUCP
. The final releases of Coherent also fully supported the iBCS COFF
binary standard, which allowed binary compatibily with SCO Unix
applications, including WordPerfect
, Lotus 1-2-3
, and several Microsoft
applications including QuickBASIC
, Microsoft Word, and MultiPlan
. There was no support for virtual memory
or demand paging
. Coherent predates both MINIX
and Linux
by many years.
A Zilog Z8000
port of Coherent was also used by the canceled Commodore 900
system.
Coherent was not Unix; the Mark Williams Company had no rights to either the Unix trademark
or the 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" and "that 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). Nigel went on to write "Ghost" - later bought out and fully commercialized as Norton Ghost
.
The Mark Williams Company closed in 1995.
Some websites offer Coherent for download, although the copyright status of it nowadays is unclear. While Coherent does not have the features of a modern Unix-like OS such as Linux, it is still a viable solution for those looking to run Unix on a very old computer such as a 286-based machine.
Sources are available for version 4.2.14. However, they don't work. Sources for the latest available version are also available, but under NDA.
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
was a Version 7 Unix
Version 7 Unix
Seventh Edition Unix, also called Version 7 Unix, Version 7 or just V7, was an important early release of the Unix operating system. V7, released in 1979, was the last Bell Laboratories release to see widespread distribution before the commercialization of Unix by AT&T in the early 1980s...
clone by the now-defunct Mark Williams Company
Mark Williams Company
The Mark Williams Company was a small software company in Chicago, Illinois that created Coherent, one of the first Unix-like operating systems for IBM PCs and several C programming language compilers. It was founded by Robert Swartz in 1980 and discontinued operations in 1995...
, originally produced for the PDP-11
PDP-11
The PDP-11 was a series of 16-bit minicomputers sold by Digital Equipment Corporation from 1970 into the 1990s, one of a succession of products in the PDP series. The PDP-11 replaced the PDP-8 in many real-time applications, although both product lines lived in parallel for more than 10 years...
in 1980. A port was introduced in 1983 as the first Unix-like
Unix-like
A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....
system for IBM PC compatible
IBM PC compatible
IBM PC compatible computers are those generally similar to the original IBM PC, XT, and AT. Such computers used to be referred to as PC clones, or IBM clones since they almost exactly duplicated all the significant features of the PC architecture, facilitated by various manufacturers' ability to...
computers
Personal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...
.
Coherent was able to run on most Intel-based PCs with Intel
Intel Corporation
Intel Corporation is an American multinational semiconductor chip maker corporation headquartered in Santa Clara, California, United States and the world's largest semiconductor chip maker, based on revenue. It is the inventor of the x86 series of microprocessors, the processors found in most...
8088
Intel 8088
The Intel 8088 microprocessor was a variant of the Intel 8086 and was introduced on July 1, 1979. It had an 8-bit external data bus instead of the 16-bit bus of the 8086. The 16-bit registers and the one megabyte address range were unchanged, however...
, 286
Intel 80286
The Intel 80286 , introduced on 1 February 1982, was a 16-bit x86 microprocessor with 134,000 transistors. Like its contemporary simpler cousin, the 80186, it could correctly execute most software written for the earlier Intel 8086 and 8088...
, 386
Intel 80386
The Intel 80386, also known as the i386, or just 386, was a 32-bit microprocessor introduced by Intel in 1985. The first versions had 275,000 transistors and were used as the central processing unit of many workstations and high-end personal computers of the time...
, and 486
Intel 80486
The Intel 80486 microprocessor was a higher performance follow up on the Intel 80386. Introduced in 1989, it was the first tightly pipelined x86 design as well as the first x86 chip to use more than a million transistors, due to a large on-chip cache and an integrated floating point unit...
processors
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
. Coherent version 3 for Intel-based PCs required at least a 286, Coherent version 4 for Intel-based PCs required at least a 386. Like a true Unix, Coherent was able to multitask
Computer multitasking
In computing, multitasking is a method where multiple tasks, also known as processes, share common processing resources such as a CPU. In the case of a computer with a single CPU, only one task is said to be running at any point in time, meaning that the CPU is actively executing instructions for...
and support multiple users. From version 4 on Coherent also had support for X11
X Window System
The X window system is a computer software system and network protocol that provides a basis for graphical user interfaces and rich input device capability for networked computers...
and MGR
ManaGeR
ManaGeR or MGR was an early windowing system originally designed and developed for Sun computers in 1984 by Stephen A. Uhler, then at Bellcore....
windowing systems.
Later versions of Coherent (version 4 and higher) supported features common in modern Unix-like systems, including a version of MicroEMACS
MicroEMACS
MicroEMACS is a small, portable Emacs-like text editor originally written by Dave Conroy in 1985, and further developed and maintained by Daniel M. Lawrence...
, access to DOS
DOS
DOS, short for "Disk Operating System", is an acronym for several closely related operating systems that dominated the IBM PC compatible market between 1981 and 1995, or until about 2000 if one includes the partially DOS-based Microsoft Windows versions 95, 98, and Millennium Edition.Related...
FAT16
File Allocation Table
File Allocation Table is a computer file system architecture now widely used on many computer systems and most memory cards, such as those used with digital cameras. FAT file systems are commonly found on floppy disks, flash memory cards, digital cameras, and many other portable devices because of...
File system
File system
A file system is a means to organize data expected to be retained after a program terminates by providing procedures to store, retrieve and update data, as well as manage the available space on the device which contain it. A file system organizes data in an efficient manner and is tuned to the...
s, an optimizing
Optimization (computer science)
In computer science, program optimization or software optimization is the process of modifying a software system to make some aspect of it work more efficiently or use fewer resources...
C
C (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
compiler
Compiler
A compiler is a computer program that transforms source code written in a programming language into another computer language...
with linker, and a modified version of Taylor UUCP
UUCP
UUCP is an abbreviation for Unix-to-Unix Copy. The term generally refers to a suite of computer programs and protocols allowing remote execution of commands and transfer of files, email and netnews between computers. Specifically, a command named uucp is one of the programs in the suite; it...
. The final releases of Coherent also fully supported the iBCS COFF
COFF
The Common Object File Format is a specification of a format for executable, object code, and shared library computer files used on Unix systems...
binary standard, which allowed binary compatibily with SCO Unix
SCO OpenServer
SCO OpenServer, previously SCO UNIX and SCO Open Desktop , is, misleadingly, a closed source version of the Unix computer operating system developed by Santa Cruz Operation and now maintained by the SCO Group....
applications, including WordPerfect
WordPerfect
WordPerfect is a word processing application, now owned by Corel.Bruce Bastian, a Brigham Young University graduate student, and BYU computer science professor Dr. Alan Ashton joined forces to design a word processing system for the city of Orem's Data General Corp. minicomputer system in 1979...
, Lotus 1-2-3
Lotus 1-2-3
Lotus 1-2-3 is a spreadsheet program from Lotus Software . It was the IBM PC's first "killer application"; its huge popularity in the mid-1980s contributed significantly to the success of the IBM PC in the corporate environment.-Beginnings:...
, and several Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
applications including QuickBASIC
QuickBASIC
Microsoft QuickBASIC is an Integrated Development Environment and compiler for the BASIC programming language that was developed by Microsoft. QuickBASIC runs mainly on DOS, though there was a short-lived version for Mac OS...
, Microsoft Word, and MultiPlan
MultiPlan
Multiplan was an early spreadsheet program developed by Microsoft. Known initially by the code name "EP" , it was introduced in 1982 as a competitor for VisiCalc....
. There was no support for virtual memory
Virtual memory
In computing, virtual memory is a memory management technique developed for multitasking kernels. This technique virtualizes a computer architecture's various forms of computer data storage , allowing a program to be designed as though there is only one kind of memory, "virtual" memory, which...
or demand paging
Demand paging
In computer operating systems, demand paging is an application of virtual memory. In a system that uses demand paging, the operating system copies a disk page into physical memory only if an attempt is made to access it...
. Coherent predates both MINIX
Minix
MINIX is a Unix-like computer operating system based on a microkernel architecture created by Andrew S. Tanenbaum for educational purposes; MINIX also inspired the creation of the Linux kernel....
and Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
by many years.
A Zilog Z8000
Zilog Z8000
The Z8000 is a 16-bit microprocessor introduced by Zilog in 1979. The architecture was designed by Bernard Peuto while the logic and physical implementation was done by Masatoshi Shima, assisted by a small group of people. The Z8000 was not Z80-compatible, and although it saw steady use well into...
port of Coherent was also used by the canceled Commodore 900
Commodore 900
The Commodore 900 was a prototype microcomputer intended for business computing and CAD purposes, and created by German Division of Commodore in 1985. The project was cancelled when Commodore bought Amiga. All of the prototypes were sold as scrap to 3rd party distributors...
system.
Coherent was not Unix; the Mark Williams Company had no rights to either the Unix trademark
Trademark
A trademark, trade mark, or trade-mark is a distinctive sign or indicator used by an individual, business organization, or other legal entity to identify that the products or services to consumers with which the trademark appears originate from a unique source, and to distinguish its products or...
or the AT&T
AT&T
AT&T Inc. is an American multinational telecommunications corporation headquartered in Whitacre Tower, Dallas, Texas, United States. It is the largest provider of mobile telephony and fixed telephony in the United States, and is also a provider of broadband and subscription television services...
/Bell Labs
Bell Labs
Bell Laboratories is the research and development subsidiary of the French-owned Alcatel-Lucent and previously of the American Telephone & Telegraph Company , half-owned through its Western Electric manufacturing subsidiary.Bell Laboratories operates its...
source code. In the early years of its existence, MWC received a visit from an AT&T
AT&T
AT&T Inc. is an American multinational telecommunications corporation headquartered in Whitacre Tower, Dallas, Texas, United States. It is the largest provider of mobile telephony and fixed telephony in the United States, and is also a provider of broadband and subscription television services...
delegation looking to determine whether MWC was infringing on AT&T Unix property. The delegation included Dennis Ritchie
Dennis Ritchie
Dennis MacAlistair Ritchie , was an American computer scientist who "helped shape the digital era." He created the C programming language and, with long-time colleague Ken Thompson, the UNIX operating system...
, 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" and "that 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
University of Waterloo
The University of Waterloo is a comprehensive public university in the city of Waterloo, Ontario, Canada. The school was founded in 1957 by Drs. Gerry Hagey and Ira G. Needles, and has since grown to an institution of more than 30,000 students, faculty, and staff...
: Tom Duff
Tom Duff
Thomas Douglas Selkirk Duff is a computer programmer. He was born in Toronto, Ontario, Canada and grew up in Toronto and Leaside. In 1974 he graduated from the University of Waterloo with a B.Math and, two years later, got an M.Sc...
, 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). Nigel went on to write "Ghost" - later bought out and fully commercialized as Norton Ghost
Ghost (software)
Ghost is a disk cloning program product sold by Symantec. Originally developed by Murray Haszard in 1995 for Binary Research, the technology was acquired in 1998 by Symantec. The name Ghost is an acronym for General Hardware-Oriented System Transfer.- History :Binary Research developed Ghost in...
.
The Mark Williams Company closed in 1995.
Some websites offer Coherent for download, although the copyright status of it nowadays is unclear. While Coherent does not have the features of a modern Unix-like OS such as Linux, it is still a viable solution for those looking to run Unix on a very old computer such as a 286-based machine.
Sources are available for version 4.2.14. However, they don't work. Sources for the latest available version are also available, but under NDA.
External links
- Andrzej Popielewicz's GNU stuff for Coherent website
- [ftp://ftp.demon.co.uk/pub/coherent/ FTP archive for Coherent at Demon Internet]
- [ftp://ftp.mayn.de/pub/really_old_stuff/coherent/ FTP archive for Coherent]
- Coherent history archive
- Installation Media for Coherent 4.2.10
- Coherent Manual (27 MB)