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Multiuser DOS is a
real-time Real-time or real time describes various operations in computing or other processes that must guarantee response times within a specified time (deadline), usually a relatively short time. A real-time process is generally one that happens in defined ...
multi-user multi-tasking
operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...
for
IBM PC The IBM Personal Computer (model 5150, commonly known as the IBM PC) is the first microcomputer released in the IBM PC model line and the basis for the IBM PC compatible de facto standard. Released on August 12, 1981, it was created by a team ...
-compatible microcomputers. An evolution of the older Concurrent CP/M-86, Concurrent DOS and Concurrent DOS 386 operating systems, it was originally developed by
Digital Research Digital Research, Inc. (DR or DRI) was a company created by Gary Kildall to market and develop his CP/M operating system and related 8-bit, 16-bit and 32-bit systems like MP/M, Concurrent DOS, FlexOS, Multiuser DOS, DOS Plus, DR DOS and ...
and acquired and further developed by
Novell Novell, Inc. was an American software and services company headquartered in Provo, Utah, that existed from 1980 until 2014. Its most significant product was the multi-platform network operating system known as Novell NetWare. Under the lead ...
in 1991. Its ancestry lies in the earlier Digital Research
8-bit In computer architecture, 8-bit Integer (computer science), integers or other Data (computing), data units are those that are 8 bits wide (1 octet (computing), octet). Also, 8-bit central processing unit (CPU) and arithmetic logic unit (ALU) arc ...
operating systems
CP/M CP/M, originally standing for Control Program/Monitor and later Control Program for Microcomputers, is a mass-market operating system created in 1974 for Intel 8080/ 85-based microcomputers by Gary Kildall of Digital Research, Inc. Initial ...
and
MP/M MP/M (Multi-Programming Monitor Control Program) is a discontinued multi-user version of the CP/M operating system, created by Digital Research developer Tom Rolander in 1979. It allowed multiple users to connect to a single computer, each us ...
, and the
16-bit 16-bit microcomputers are microcomputers that use 16-bit microprocessors. A 16-bit register can store 216 different values. The range of integer values that can be stored in 16 bits depends on the integer representation used. With the two mos ...
single-tasking
CP/M-86 CP/M-86 was a version of the CP/M operating system that Digital Research (DR) made for the Intel 8086 and Intel 8088. The system commands are the same as in CP/M-80. Executable files used the relocatable .CMD file format. Digital Research als ...
which evolved from CP/M. When Novell abandoned Multiuser DOS in 1992, the three master
value-added reseller A value-added reseller (VAR) is a company that adds features or services to an existing product, then resells it (usually to end-users) as an integrated product or complete "turn-key" solution. This practice occurs commonly in the electronics or IT ...
s (VARs) DataPac Australasia,
Concurrent Controls Multiuser DOS is a real-time multi-user multi-tasking operating system for IBM PC-compatible microcomputers. An evolution of the older Concurrent CP/M-86, Concurrent DOS and Concurrent DOS 386 operating systems, it was originally developed by ...
and
Intelligent Micro Software Multiuser DOS is a real-time multi-user multi-tasking operating system for IBM PC-compatible microcomputers. An evolution of the older Concurrent CP/M-86, Concurrent DOS and Concurrent DOS 386 operating systems, it was originally developed by ...
were allowed to take over and continued independent development into Datapac Multiuser DOS and System Manager, CCI Multiuser DOS, and IMS Multiuser DOS and REAL/32. The
FlexOS FlexOS is a discontinued modular real-time multiuser computer multitasking, multitasking operating system (RTOS) designed for computer-integrated manufacturing, laboratory, retail and financial markets. Developed by Digital Research's Flexible ...
line, which evolved from
Concurrent DOS 286 Multiuser DOS is a real-time multi-user multi-tasking operating system for IBM PC-compatible microcomputers. An evolution of the older Concurrent CP/M-86, Concurrent DOS and Concurrent DOS 386 operating systems, it was originally developed by ...
and
Concurrent DOS 68K Multiuser DOS is a real-time multi-user multi-tasking operating system for IBM PC-compatible microcomputers. An evolution of the older Concurrent CP/M-86, Concurrent DOS and Concurrent DOS 386 operating systems, it was originally developed by ...
, was sold off to Integrated Systems, Inc. (ISI) in July 1994.


Concurrent CP/M-86

The initial version of CP/M-86 1.0 (with BDOS 2.x) was adapted and became available to the
IBM PC The IBM Personal Computer (model 5150, commonly known as the IBM PC) is the first microcomputer released in the IBM PC model line and the basis for the IBM PC compatible de facto standard. Released on August 12, 1981, it was created by a team ...
in 1982. It was commercially unsuccessful as IBM's PC DOS 1.0 offered much the same facilities for a considerably lower price. Neither PC DOS nor CP/M-86 could fully exploit the power and capabilities of the new 16-bit machine. It was soon supplemented by an implementation of CP/M's multitasking 'big brother', MP/M-86 2.0, since September 1981. This turned a PC into a multiuser machine capable of supporting multiple
concurrent user In computer science, the number of concurrent users (sometimes abbreviated CCU) for a resource in a location, with the location being a computing network or a single computer, refers to the total number of people simultaneously accessing or using t ...
s using
dumb terminal A computer terminal is an electronic or electromechanical hardware device that can be used for entering data into, and transcribing data from, a computer or a computing system. The teletype was an example of an early-day hard-copy terminal and ...
s attached by
serial port In computing, a serial port is a serial communication interface through which information transfers in or out sequentially one bit at a time. This is in contrast to a parallel port, which communicates multiple bits simultaneously in parallel. ...
s. The environment presented to each user made it seem as if they had the entire computer to themselves. Since terminals cost a fraction of the then-substantial price of a complete PC, this offered considerable cost savings, as well as facilitating multi-user applications such as accounts or stock control in a time when PC networks were rare, very expensive and difficult to implement. CP/M-86 1.1 (with
BDOS CP/M, originally standing for Control Program/Monitor and later Control Program for Microcomputers, is a mass-market operating system created in 1974 for Intel 8080/ 85-based microcomputers by Gary Kildall of Digital Research, Inc. Initiall ...
2.2) and MP/M-86 2.1 were merged to create Concurrent CP/M-86 3.0 (also known as CCP/M-86) with BDOS 3.0 in late 1982.
Kathryn Strutynski Kathryn Betty Strutynski (''née'' Latimer) (5 February 1931 – 9 April 2010) was a mathematician and computer scientist, and attended University at Brigham Young University and the Naval Postgraduate School. Besides jobs at Pan Am Airways and ...
, the project manager for CP/M-86, was also the project manager for Concurrent CP/M-86. One of its designers was Francis "Frank" R. Holsworth. Initially, this was a single-user operating system supporting true multi-tasking of up to four (in its default configuration) CP/M-86 compatible programs. Like its predecessors it could be configured for
multi-processor Multiprocessing is the use of two or more central processing units (CPUs) within a single computer system. The term also refers to the ability of a system to support more than one processor or the ability to allocate tasks between them. There ar ...
support (see e.g. Concurrent CP/M-86/80) and also added "virtual screens" letting an operator switch between the interactions of multiple programs. Later versions supported dumb terminals and so could be deployed as multiuser systems. Concurrent CP/M-86 3.1 (BDOS 3.1) shipped on 21 February 1984.


Adaptations


Concurrent CP/M-86 with Windows

In February 1984 Digital Research also offered a version of Concurrent CP/M-86 with windowing capabilities named Concurrent CP/M with Windows for the IBM Personal Computer and Personal Computer XT.


Concurrent CP/M-86/80

This was an adaptation of Concurrent CP/M-86 for the LSI-M4,
LSI Octopus LSI may refer to: Science and technology * Large-scale integration, integrated circuits with tens of thousands of transistors * Latent semantic indexing, a technique in natural language processing * LSI-11, an early large-scale integration comp ...
and
CAL PC Cal or CAL may refer to: Arts and entertainment * ''Cal'' (novel), a 1983 novel by Bernard MacLaverty * "Cal" (short story), a science fiction short story by Isaac Asimov * ''Cal'' (1984 film), an Irish drama starring John Lynch and Helen Mir ...
computers. These machines had both 16-bit and 8-bit processors, because in the early days of 16-bit personal computing, 8-bit software was more available and often ran faster than the corresponding 16-bit software. Concurrent CP/M-86/80 allowed users to run both CP/M (8-bit) and CP/M-86 (16-bit) applications. When a command was entered, the operating system ran the corresponding application on either the 8-bit or the 16-bit processor, depending on whether the executable file had a
.COM The domain name .com is a top-level domain (TLD) in the Domain Name System (DNS) of the Internet. Added at the beginning of 1985, its name is derived from the word ''commercial'', indicating its original intended purpose for domains registere ...
or .CMD extension. It emulated a CP/M environment for 8-bit programs by translating CP/M system calls into CP/M-86 system calls, which were then executed by the 16-bit processor.


Concurrent DOS

In August 1983,
Bruce Skidmore The English language name Bruce arrived in Scotland with the Normans, from the place name Brix, Manche in Normandy, France, meaning "the willowlands". Initially promulgated via the descendants of king Robert the Bruce (1274−1329), it has been a ...
, Raymond D. Pedrizetti, Dave Brown and
Gordon Edmonds Gordon may refer to: People * Gordon (given name), a masculine given name, including list of persons and fictional characters * Gordon (surname), the surname * Gordon (slave), escaped to a Union Army camp during the U.S. Civil War * Clan Gordon, ...
teamed up to create PC-MODE, an optional module for Concurrent CP/M-86 3.1 (with BDOS 3.1) to provide basic compatibility with
PC DOS 1.1 IBM PC DOS, an acronym for IBM Personal Computer Disk Operating System, is a discontinued disk operating system for IBM PC compatibles. It was manufactured and sold by IBM from the early 1980s into the 2000s. Developed by Microsoft, it was also ...
(and
MS-DOS 1.1 MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few oper ...
). This was shown publicly at
COMDEX COMDEX (an abbreviation of COMputer Dealers' EXhibition) was a computer expo trade show held in the Las Vegas Valley of Nevada, United States, each November from 1979 to 2003. It was one of the largest computer trade shows in the world, usually ...
in December 1983 and shipped in March 1984 as Concurrent DOS 3.1 (a.k.a. CDOS with BDOS 3.1) to hardware vendors. Simple DOS applications, which did not directly access the screen or other hardware, could be run. For example, although a console program such as
PKZIP PKZIP is a file archiving computer program, notable for introducing the popular ZIP file format. PKZIP was first introduced for MS-DOS on the IBM-PC compatible platform in 1989. Since then versions have been released for a number of other ...
worked perfectly and offered more facilities than the CP/M-native
ARC ARC may refer to: Business * Aircraft Radio Corporation, a major avionics manufacturer from the 1920s to the '50s * Airlines Reporting Corporation, an airline-owned company that provides ticket distribution, reporting, and settlement services * ...
archiver, applications which performed screen manipulations, such as the
WordStar WordStar is a word processor application for microcomputers. It was published by MicroPro International and originally written for the CP/M-80 operating system, and later written also for MS-DOS and other 16-bit PC OSes. Rob Barnaby was the sol ...
word processor A word processor (WP) is a device or computer program that provides for input, editing, formatting, and output of text, often with some additional features. Word processor (electronic device), Early word processors were stand-alone devices ded ...
for DOS, would not, and native Concurrent CP/M (or CP/M-86) versions were required. While Concurrent DOS 3.1 up to 4.1 had been developed in the US, OEM adaptations and localizations were carried out by
DR Europe Digital Research, Inc. (DR or DRI) was a company created by Gary Kildall to market and develop his CP/M operating system and related 8-bit, 16-bit and 32-bit systems like MP/M, Concurrent DOS, FlexOS, Multiuser DOS, DOS Plus, DR DOS and GE ...
's OEM Support Group in Newbury, UK, since 1983. Digital Research positioned
Concurrent DOS 4.1 Multiuser DOS is a Real-time operating system, real-time multi-user multi-tasking operating system for IBM Personal Computer, IBM PC-compatible microcomputers. An evolution of the older Concurrent CP/M-86, Concurrent DOS and Concurrent DOS 386 ...
with
GEM A gemstone (also called a fine gem, jewel, precious stone, or semiprecious stone) is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rocks (such as lapis lazuli, opal, a ...
as alternative for IBM's
TopView TopView is the first object-oriented, multitasking, and windowing, personal computer operating environment for PC DOS developed by IBM, announced in August 1984 and shipped in March 1985. TopView provided a text-mode (although it also ran in gr ...
in 1985.


Concurrent PC DOS

Concurrent DOS 3.2 (with BDOS 3.2) in 1984 was compatible with applications for CP/M-86 1.x, Concurrent CP/M-86 3.x and PC DOS 2.0. It was available for many different hardware platforms. The version with an IBM PC compatible BIOS/XIOS was named Concurrent PC DOS 3.2. Kathryn Strutynski was the product manager for Concurrent PC DOS.


Concurrent DOS 68K and FlexOS 68K

Efforts being part of a cooperation with
Motorola Motorola, Inc. () was an American Multinational corporation, multinational telecommunications company based in Schaumburg, Illinois, United States. After having lost $4.3 billion from 2007 to 2009, the company split into two independent p ...
since 1984 led to the development of Concurrent DOS 68K in
Austin Austin is the capital city of the U.S. state of Texas, as well as the seat and largest city of Travis County, with portions extending into Hays and Williamson counties. Incorporated on December 27, 1839, it is the 11th-most-populous city ...
, Texas, as a successor to
CP/M-68K CP/M, originally standing for Control Program/Monitor and later Control Program for Microcomputers, is a mass-market operating system created in 1974 for Intel 8080/ 85-based microcomputers by Gary Kildall of Digital Research, Inc. Initiall ...
written in C. One of its main architects was Francis "Frank" R. Holsworth (using
siglum Scribal abbreviations or sigla (singular: siglum) are abbreviations used by ancient and medieval scribes writing in various languages, including Latin, Greek, Old English and Old Norse. In modern manuscript editing (substantive and mechanica ...
FRH). Concurrent DOS 68K 1.0 became available for OEM evaluation in early 1985. The effort received considerable funding worth several million dollars from Motorola and was designed for their
68000 The Motorola 68000 (sometimes shortened to Motorola 68k or m68k and usually pronounced "sixty-eight-thousand") is a 16/32-bit complex instruction set computer (CISC) microprocessor, introduced in 1979 by Motorola Semiconductor Products Sector ...
/
68010 The Motorola MC68010 processor is a 16/32-bit microprocessor from Motorola, released in 1982 as the successor to the Motorola 68000. It fixes several small flaws in the 68000, and adds a few features. The 68010 is pin-compatible with the 68000, ...
processors. Like the earlier
GEMDOS GEM (for Graphics Environment Manager) is an operating environment released by Digital Research (DRI) in 1985 for use with the DOS operating system on Intel 8088 and Motorola 68000 microprocessors. GEM is known primarily as the graphical user i ...
system for 68000 processors it initially ran on the Motorola VME/10 development system. Concurrent DOS 68K 1.20/1.21 was available in April 1986, offered for about to OEMs. This system evolved into
FlexOS 68K FlexOS is a discontinued modular real-time multiuser multitasking operating system (RTOS) designed for computer-integrated manufacturing, laboratory, retail and financial markets. Developed by Digital Research's Flexible Automation Business U ...
in late 1986. Known versions include: * Concurrent DOS 68K 1.0 (1985) * Concurrent DOS 68K 1.1 * Concurrent DOS 68K 1.20 (April 1986, 1986-05-27) * Concurrent DOS 68K 1.21 (1986)


Concurrent DOS 286 and FlexOS 286

In parallel to the Concurrent DOS 68K effort, Digital Research also previewed Concurrent DOS 286 in cooperation with
Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California. It is the world's largest semiconductor chip manufacturer by revenue, and is one of the developers of the x86 seri ...
in January 1985. This was based on MP/M-286 and Concurrent CP/M-286, on which Digital Research had worked on since 1982. Concurrent DOS 286 was a complete rewrite in the
C language C (''pronounced like the letter c'') is a general-purpose computer programming language. It was created in the 1970s by Dennis Ritchie, and remains very widely used and influential. By design, C's features cleanly reflect the capabilities o ...
based on a new system architecture with dynamically loadable device drivers instead of a static BIOS or XIOS. One of its main architects was Francis "Frank" R. Holsworth. The operating system would function strictly in
80286 The Intel 80286 (also marketed as the iAPX 286 and often called Intel 286) is a 16-bit microprocessor that was introduced on February 1, 1982. It was the first 8086-based CPU with separate, non-multiplexed address and data buses and also the fi ...
native mode, allowing protected mode multi-user, multitasking operation while running 8086 emulation. While this worked on the B-1
step Step(s) or STEP may refer to: Common meanings * Stairs#Step, Steps, making a staircase * Walking * Dance move * Military step, or march ** Marching Arts Films and television * Steps (TV series), ''Steps'' (TV series), Hong Kong * Step (film), ' ...
of prototype chip samples, Digital Research, with evaluation copies of their operating system already shipping in April, discovered problems with the emulation on the production level C-1 step of the processor in May, which would not allow Concurrent DOS 286 to run 8086 software in protected mode. The release of Concurrent DOS 286 had been scheduled for late May, but was delayed until Intel could develop a new version of the chip. In August, after extensive testing E-1 step samples of the 80286, Digital Research said that Intel had corrected all documented 286
errata An erratum or corrigendum (plurals: errata, corrigenda) (comes from la, errata corrige) is a correction of a published text. As a general rule, publishers issue an erratum for a production error (i.e., an error introduced during the publishing pro ...
, but that there were still undocumented chip performance problems with the prerelease version of Concurrent DOS 286 running on the E-1 step. Intel said that the approach Digital Research wished to take in emulating 8086 software in protected mode differed from the original specifications; nevertheless they incorporated into the E-2 step minor changes in the
microcode In processor design, microcode (μcode) is a technique that interposes a layer of computer organization between the central processing unit (CPU) hardware and the programmer-visible instruction set architecture of a computer. Microcode is a laye ...
that allowed Digital Research to run emulation mode much faster (see
LOADALL LOADALL is the common name for two different, undocumented machine instructions of Intel 80286 and Intel 80386 processors, which allow access to areas of the internal processor state that are normally outside of the IA-32 API scope, like ''descr ...
). These same limitations affected
FlexOS 286 FlexOS is a discontinued modular real-time multiuser multitasking operating system (RTOS) designed for computer-integrated manufacturing, laboratory, retail and financial markets. Developed by Digital Research's Flexible Automation Business U ...
version 1.x, a reengineered derivation of Concurrent DOS 286, which was developed by Digital Research's new Flexible Automation Business Unit in Monterey, California, since 1986. Later versions added compatibility with PC DOS 2.x and 3.x. Known versions include: * Concurrent DOS 286 1.0 (1985) * Concurrent DOS 286 1.1 (1986-01-07) * Concurrent DOS 286 1.2 (1986) *
FlexOS 286 1.3 FlexOS is a discontinued modular real-time multiuser multitasking operating system (RTOS) designed for computer-integrated manufacturing, laboratory, retail and financial markets. Developed by Digital Research's Flexible Automation Business U ...
(November 1986) *
FlexOS 286 1.31 FlexOS is a discontinued modular real-time multiuser computer multitasking, multitasking operating system (RTOS) designed for computer-integrated manufacturing, laboratory, retail and financial markets. Developed by Digital Research's Flexible ...
(May 1987)


Concurrent DOS XM and Concurrent DOS 386

The OEM Support Group was relocated into Digital Research's newly created European Development Centre (EDC) in
Hungerford Hungerford is a historic market town and civil parish in Berkshire, England, west of Newbury, east of Marlborough, northeast of Salisbury and 60 miles (97 km) west of London. The Kennet and Avon Canal passes through the town alongside the ...
, UK in 1986, which started to take over further development of the Concurrent DOS family since Concurrent DOS 4.11, including siblings like
DOS Plus DOS Plus (erroneously also known as DOS+) was the first operating system developed by Digital Research's OEM Support Group in Newbury, Berkshire, UK, first released in 1985. DOS Plus 1.0 was based on CP/M-86 Plus combined with the PCMODE e ...
and successors. Developed in Hungerford, UK, versions 5 and 6 (Concurrent DOS XM, with XM standing for
Expanded Memory In DOS memory management, expanded memory is a system of bank switching that provided additional memory to DOS programs beyond the limit of conventional memory (640 KiB). ''Expanded memory'' is an umbrella term for several incompatible techn ...
) could
bank switch Bank switching is a technique used in computer design to increase the amount of usable memory beyond the amount directly addressable by the processor instructions. It can be used to configure a system differently at different times; for example ...
up to 8 MB of
EEMS In DOS memory management, expanded memory is a system of bank switching that provided additional memory to DOS programs beyond the limit of conventional memory (640 KiB). ''Expanded memory'' is an umbrella term for several incompatible techn ...
to provide a real-mode environment to run multiple CP/M-86 and DOS programs concurrently and support up to three users (one local and up to two hooked up via serial terminals). In 1987, Concurrent DOS 86 was rewritten to become Concurrent DOS 386, still a continuation of the classical XIOS & BDOS architecture. This ran on machines equipped with the
Intel 80386 The Intel 386, originally released as 80386 and later renamed i386, is a 32-bit microprocessor introduced in 1985. The first versions had 275,000 transistorsvirtualizing In computing, virtualization or virtualisation (sometimes abbreviated v12n, a numeronym) is the act of creating a virtual (rather than actual) version of something at the same abstraction level, including virtual computer hardware platforms, stor ...
the hardware, allowing most DOS applications to run unmodified under Concurrent DOS 386, even on terminals. The OS supported concurrent multiuser file access, allowing multiuser applications to run as if they were on individual PCs attached to a network
server Server may refer to: Computing *Server (computing), a computer program or a device that provides functionality for other programs or devices, called clients Role * Waiting staff, those who work at a restaurant or a bar attending customers and su ...
. Concurrent DOS 386 allowed a single server to support a number of users on dumb terminals or inexpensive low-specification PCs running terminal emulation software, without the need for expensive workstations and then-expensive network cards. It was a true multiuser system; several users could use a single database with
record locking Record locking is the technique of preventing simultaneous access to data in a database, to prevent inconsistent results. The classic example is demonstrated by two bank clerks attempting to update the same bank account for two different transacti ...
to prevent mutual interference. Concurrent DOS 6.0 represented also the starting point for the
DR DOS DR-DOS (written as DR DOS, without a hyphen, in versions up to and including 6.0) is a disk operating system for IBM PC compatibles. Upon its introduction in 1988, it was the first DOS attempting to be compatible with IBM PC DOS and MS-D ...
family, which was carved out of it. Known versions include: * DR Concurrent PC DOS XM 5.0 (BDOS 5.0) * DR Concurrent DOS XM 5.0 (BDOS 5.0, October 1986) * DR Concurrent DOS XM 5.1 (BDOS 5.1?, January 1987) * DR Concurrent DOS XM 5.2 (BDOS 5.2?, September 1987) * DR Concurrent DOS XM 6.0 (BDOS 6.0, 1987-11-18), 6.01 (1987) * DR Concurrent DOS XM 6.2 (BDOS 6.2), 6.21 ; ; * DR Concurrent DOS 386 1.0 (BDOS 5.0?, 1987) * DR Concurrent DOS 386 1.1 (BDOS 5.2?, September 1987) * DR Concurrent DOS 386 2.0 (BDOS 6.0, 1987-11-18), 2.01 * DR Concurrent DOS 386 3.0 (BDOS 6.2, December 1988, January 1989), 3.01 (1989-05-19), 3.02 (1989) Concurrent PC DOS XM 5.0 emulated IBM PC DOS 2.10, whereas Concurrent DOS XM 6.0 and Concurrent DOS 386 2.0 were compatible with IBM PC DOS 3.30.


Adaptations

Known CCI Concurrent DOS adaptations by Concurrent Controls, Inc. include: * CCI Concurrent DOS 386 1.12 (BDOS 5.0?, October 1987) * CCI Concurrent DOS 386 2.01 (BDOS 6.0?, May 1988) * CCI Concurrent DOS 386 3.01 (BDOS 6.2?, March 1989) * CCI Concurrent DOS 386 3.02 (April 1990) * CCI Concurrent DOS 386 3.03 (March 1991) * CCI Concurrent DOS 386 3.04 (July 1991) aka "CCI Concurrent DOS 4.0" * CCI Concurrent DOS 3.05 R1 (1992-02), R2 (1992), R3+R4 (1992), R5+R6 (1992), R7+R8 (1993), R9+R10 (1993), R11 (August 1993) * CCI Concurrent DOS 3.06 R1 (December 1993), R2+R3 (1994), R4+R5+R6 (1994), R7 (July 1994) * CCI Concurrent DOS 3.07 R1 (March 1995), R2 (1995), R3 (1996), R4 (1996), R5 (1997), R6 (1997), R7 (June 1998) * CCI Concurrent DOS 3.08 * CCI Concurrent DOS 3.10 R1 (2003-10-05) Other adaptations include: *
Apricot An apricot (, ) is a fruit, or the tree that bears the fruit, of several species in the genus ''Prunus''. Usually, an apricot is from the species '' P. armeniaca'', but the fruits of the other species in ''Prunus'' sect. ''Armeniaca'' are also ...
Concurrent DOS 386 2.01 (1987) for Apricot Quad Version Level 4.3


Multiuser DOS

Later versions of Concurrent DOS 386 incorporated some of the enhanced functionality of DR's later single-user PC DOS clone
DR DOS 5.0 DR-DOS (written as DR DOS, without a hyphen, in versions up to and including 6.0) is a disk operating system for IBM PC compatibles. Upon its introduction in 1988, it was the first DOS attempting to be compatible with IBM PC DOS and MS-D ...
, after which the product was given the more explanatory name "Multiuser DOS" (a.k.a. MDOS), starting with version 5.0 (with BDOS 6.5) in 1991. Multiuser DOS suffered from several technical limitations that restricted its ability to compete with
LANs Lans or LANS may refer to: Places * Lans, Tyrol, a municipality in Tyrol, Austria * Lake Lans, a lake near Lans, Tyrol France * Lans, Saône-et-Loire * Lans-en-Vercors, a community near Grenoble in the Vercors * Villard-de-Lans, a community and s ...
based on
PC DOS PC or pc may refer to: Arts and entertainment * Player character or playable character, a fictional character controlled by a human player, usually in role-playing games or computer games * ''Port Charles'', an American daytime TV soap opera * ...
. It required its own special
device driver In computing, a device driver is a computer program that operates or controls a particular type of device that is attached to a computer or automaton. A driver provides a software interface to hardware devices, enabling operating systems and ot ...
s for much common hardware, as PC DOS drivers were not multiuser or multi-tasking aware. Driver installation was more complex than the simple PC DOS method of copying the files onto the boot disk and modifying CONFIG.SYS appropriately it was necessary to relink the Multiuser DOS
kernel Kernel may refer to: Computing * Kernel (operating system), the central component of most operating systems * Kernel (image processing), a matrix used for image convolution * Compute kernel, in GPGPU programming * Kernel method, in machine learnin ...
(known as a ''nucleus'') using the
SYSGEN CONFIG.SYS is the primary configuration file for the DOS and OS/2 operating systems. It is a special ASCII text file that contains user-accessible setup or configuration directives evaluated by the operating system's DOS BIOS (typically residing ...
command. Multiuser DOS was also unable to use many common PC DOS additions such as
network stack The protocol stack or network stack is an implementation of a computer networking protocol suite or protocol family. Some of these terms are used interchangeably but strictly speaking, the ''suite'' is the definition of the communication protoco ...
s, and it was limited in its ability to support later developments in the PC-compatible world, such as
graphics adaptor A graphics card (also called a video card, display card, graphics adapter, VGA card/VGA, video adapter, display adapter, or mistakenly GPU) is an expansion card which generates a feed of output images to a display device, such as a computer mo ...
s,
sound card A sound card (also known as an audio card) is an internal expansion card that provides input and output of audio signals to and from a computer under the control of computer programs. The term ''sound card'' is also applied to external audio i ...
s,
CD-ROM A CD-ROM (, compact disc read-only memory) is a type of read-only memory consisting of a pre-pressed optical compact disc that contains data. Computers can read—but not write or erase—CD-ROMs. Some CDs, called enhanced CDs, hold both comput ...
drives and mice. Although many of these were soon rectified for example, graphical terminals were developed, allowing users to use CGA,
EGA Ega or EGA may refer to: Military * East German Army, the common western name for the National People's Army * Eagle, Globe, and Anchor, the emblem of the United States Marine Corps People * Aega (mayor of the palace), 7th-century noble of Neus ...
and
VGA Video Graphics Array (VGA) is a video display controller and accompanying de facto graphics standard, first introduced with the IBM PS/2 line of computers in 1987, which became ubiquitous in the PC industry within three years. The term can now ...
software it was less flexible in this regard than a network of individual PCs, and as the prices of these fell, it became less and less competitive, although it still offered benefits in terms of management and lower total cost of ownership. As a multi-user operating system its price was higher than a single-user system, of course, and it required special device drivers, unlike single-user multitasking DOS add-ons such as Quarterdeck's
DESQview DESQview (DV) is a text mode multitasking operating environment developed by Quarterdeck Office Systems which enjoyed modest popularity in the late 1980s and early 1990s. Running on top of DOS, it allows users to run multiple programs concurrentl ...
. Unlike MP/M, it never became popular for single-user but multitasking use. When Novell acquired Digital Research in 1991 and abandoned Multiuser DOS in 1992, the three Master VARs DataPac Australasia, Concurrent Controls and Intelligent Micro Software were allowed to license the source code of the system to take over and continue independent development of their derivations in 1994. Known versions include: * DR Multiuser DOS 5.00 (1991), 5.01 * Novell DR Multiuser DOS 5.10 (1992-04-13), 5.11 * Novell DR Multiuser DOS 5.13 (BDOS 6.6, 1992) All versions of Digital Research and Novell DR Multiuser DOS reported themselves as "IBM PC DOS" version 3.31.


Adaptations


DataPac Australasia

Known versions by DataPac Australasia Pty Limited include: * Datapac Multiuser DOS 5.0 * Datapac Multiuser DOS 5.1 (BDOS 6.6) * Datapac System Manager 7.0 (1996-08-22) In 1997, Datapac was bought by
Citrix Systems, Inc. Citrix Systems, Inc. is an American multinational cloud computing and virtualization technology company that provides server, application and desktop virtualization, networking, software as a service (SaaS), and cloud computing technologies. C ...
, and System Manager was abandoned soon after. In 2002 the Sydney-based unit was spun out into Citrix' Advanced Products Group.


Concurrent Controls

Known CCI Multiuser DOS versions by Concurrent Controls, Inc. (CCI) include: * CCI Multiuser DOS 7.00 * CCI Multiuser DOS 7.10 * CCI Multiuser DOS 7.21 * CCI Multiuser DOS 7.22 R1 (September 1996), R2 (1996), R3 (1997), R4 GOLD/PLUS/LITE (BDOS 6.6, 1997-02-10), R5 GOLD (1997), R6 GOLD (1997), R7 GOLD (June 1998), R8 GOLD, R9 GOLD, R10 GOLD, R11 GOLD (2000-09-25), R12 GOLD (2002-05-15), R13 GOLD (2002-07-15), R14 GOLD (2002-09-13), R15 GOLD, R16 GOLD (2003-10-10), R17 GOLD (2004-02-09), R18 GOLD (2005-04-21) All versions of CCI Multiuser DOS report themselves as "IBM PC DOS" version 3.31. Similar to
SETVER This article presents a list of commands used by DOS operating systems, especially as used on x86-based IBM PC compatibles (PCs). Other DOS operating systems are not part of the scope of this list. In DOS, many standard system commands were pro ...
under
DOS DOS is shorthand for the MS-DOS and IBM PC DOS family of operating systems. DOS may also refer to: Computing * Data over signalling (DoS), multiplexing data onto a signalling channel * Denial-of-service attack (DoS), an attack on a communicatio ...
, this can be changed using the Multiuser DOS utility. In 1999, CCI changed its name to Applica, Inc. In 2002 Applica Technology became Aplycon Technologies, Inc.


Intelligent Micro Software, Itera and Integrated Solutions


=DOS 386 Professional

=


=IMS Multiuser DOS

= Known adaptations of IMS Multiuser DOS include: * IMS Multiuser DOS Enhanced Release 5.1 (1992) * IMS Multiuser DOS 5.11 * IMS Multiuser DOS 5.14 * IMS Multiuser DOS 7.0 * IMS Multiuser DOS 7.1 (BDOS 6.7, 1994) All versions of IMS Multiuser DOS report themselves as "IBM PC DOS" version 3.31.


=REAL/32

= Intelligent Micro Software Ltd. (IMS) of Thatcham, UK, acquired a license to further develop Multiuser DOS from Novell in 1994 and renamed their product REAL/32 in 1995. Similar to
FlexOS FlexOS is a discontinued modular real-time multiuser computer multitasking, multitasking operating system (RTOS) designed for computer-integrated manufacturing, laboratory, retail and financial markets. Developed by Digital Research's Flexible ...
/
4690 OS 4690 Operating System (sometimes shortened to 4690 OS or 4690) is a specially designed point of sale (POS) operating system, originally sold by IBM. In 2012, IBM sold its retail business, including this product, to Toshiba, which assumed support. ...
before, IBM in 1995 licensed REAL/32 7.50 to bundle it with their 4695 POS terminals. IMS REAL/32 versions: * IMS REAL/32 7.50 (BDOS 6.8, 1995-07-01), 7.51 (BDOS 6.8), 7.52 (BDOS 6.9), 7.53 (BDOS 6.9, 1996-04-01), 7.54 (BDOS 6.9, 1996-08-01) * IMS REAL/32 7.60 (BDOS 6.9, February 1997), 7.61, 7.62, 7.63 * IMS REAL/32 7.70 (November 1997), 7.71, 7.72, 7.73, 7.74 (1998) * IMS REAL/32 7.80, 7.81 (February 1999), 7.82, 7.83 (BDOS 6.10) * IMS REAL/32 7.90 (1999), 7.91, 7.92 * ITERA IMS REAL/32 7.93 (June 2002), 7.94 (BDOS 6.13, 2003-01-31) * Integrated Solutions IMS REAL/32 7.95 REAL/32 7.50 to 7.74 report themselves as "IBM PC DOS" version 3.31, whereas 7.80 and higher report a version of 6.20. LBA and
FAT32 File Allocation Table (FAT) is a file system developed for personal computers. Originally developed in 1977 for use on floppy disks, it was adapted for use on hard disks and other devices. It is often supported for compatibility reasons by c ...
support was added with REAL/32 7.90 in 1999. On 19 April 2002, Intelligent Micro Software Ltd. filed for insolvency and was taken over by one of its major customers, Barry Quittenton's Itera Ltd. This company was dissolved on 2006-03-28. As of 2010 REAL/32 was supplied by Integrated Solutions of Thatcham, UK, but the company, at the same address, was later listed as builders.


=REAL/NG

= REAL/NG was IMS' attempt to create the "Next Generation" of REAL/32, also named "REAL/32 for the internet age". REAL/NG promised "increased range of hardware from PCs to x86 multi-processor server systems". Advertised feature list, as of 2003: * Runs with Red Hat 7.3 or later version of
Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which ...
* Backward compatible with DOS and REAL/32 * Max 65535 virtual consoles; each of these can be a user * No Linux expertise required * Administration/setup/upgrade by web browser (local and remote) * Supplied with
TCP/IP The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the set of communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suit ...
Linux-/Windows-based terminal emulator for the number of users purchased * Print and file sharing built in * Drive mapping between Linux and REAL/NG servers built in * User hardware support * Increased performance * Vastly increased TPA * Multi-processor support * Improved hardware support * Built-in firewall support * Very low cost per seat * Low total cost of ownership * Supplied on CD * Supplied with a set of Red Hat CDs By 10 December 2003, IMS made "REALNG V1.60-V1.19-V1.12" available, which, based on the
Internet Archive The Internet Archive is an American digital library with the stated mission of "universal access to all knowledge". It provides free public access to collections of digitized materials, including websites, software applications/games, music, ...
, seems to be the latest release. By 2005, the realng.com website was mirroring the IMS main website, and had no mention of REAL/NG, only REAL/32.


Application software

While the various releases of this operating system had increasing ability to run DOS programs, software written for the platform could take advantage of its features by using function calls specifically suitable for multiuser operation. It used
pre-emptive multitasking In computing, preemption is the act of temporarily interrupting an executing task, with the intention of resuming it at a later time. This interrupt is done by an external scheduler with no assistance or cooperation from the task. This preempt ...
, preventing badly-written applications from delaying other processes by retaining control of the processor. To this day, Multiuser DOS is supported by popular
SSL/TLS Transport Layer Security (TLS) is a cryptographic protocol designed to provide communications security over a computer network. The protocol is widely used in applications such as email, instant messaging, and voice over IP, but its use in securi ...
libraries such as
wolfSSL wolfSSL is a small, portable, embedded SSL/TLS library targeted for use by embedded systems developers. It is an open source implementation of TLS (SSL 3.0, TLS 1.0, 1.1, 1.2, 1.3, and DTLS 1.0, 1.2, and 1.3) written in the C programming lan ...
. The
API An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software Interface (computing), interface, offering a service to other pieces of software. A document or standa ...
provided support for blocking and non-blocking
message queue In computer science, message queues and mailboxes are software-engineering components typically used for inter-process communication (IPC), or for inter- thread communication within the same process. They use a queue for messaging – the ...
s, mutual-exclusion queues, the ability to create sub-process threads which executed independently from the parent, and a method of pausing execution which did not waste processor cycles, unlike idle loops used by single-user operating systems. Applications were started as "attached" to a
console Console may refer to: Computing and video games * System console, a physical device to operate a computer ** Virtual console, a user interface for multiple computer consoles on one device ** Command-line interface, a method of interacting with ...
. However, if an application did not need user interaction it could "detach" from the console and run as a
background process A background process is a computer process that runs ''behind the scenes'' (i.e., in the background) and without user intervention. Typical tasks for these processes include logging, system monitoring, scheduling, and user notification. The backgr ...
, later reattaching to a console if needed. Another key feature was that the
memory management Memory management is a form of resource management applied to computer memory. The essential requirement of memory management is to provide ways to dynamically allocate portions of memory to programs at their request, and free it for reuse when ...
supported a "shared" memory model for processes (in addition to the usual models available to normal DOS programs). In the shared memory model the "code" and "data" sections of a program were isolated from each other. Because the "code" contained no modifiable data, code sections in memory could be shared by several processes running the same program, thereby reducing memory requirements. Programs written, or adapted, for any multitasking platform need to avoid the technique used by single-tasking systems of going into endless loops until interrupted when, for example, waiting for a user to press a key; this wasted processor time that could be used by other processes. Instead, Concurrent DOS provided an API call which a process could call to "sleep" for a period of time. Later versions of the Concurrent DOS kernel included Idle Detection, which monitored
DOS API The DOS API is an API which originated with 86-DOS and is used in MS-DOS/ PC DOS and other DOS-compatible operating systems. Most calls to the DOS API are invoked using software interrupt 21h ( INT 21h). By calling INT 21h with a subfunction ...
calls to determine whether the application was doing useful work or in fact idle, in which case the process was suspended allowing other processes to run. Idle Detection was the catalyst for the patented
DR-DOS DR-DOS (written as DR DOS, without a hyphen, in versions up to and including 6.0) is a disk operating system for IBM PC compatibles. Upon its introduction in 1988, it was the first DOS attempting to be compatible with IBM PC DOS and MS-D ...
Dynamic Idle Detection power management feature invented in 1989 by Roger Alan Gross and John P. Constant and marketed as
BatteryMAX BatteryMAX is an idle detection system used for computer power management under operating system control developed at Digital Research, Inc.'s European Development Centre (EDC) in Hungerford, UK. It was created to address the new genre of p ...
.


See also

*
CP/M CP/M, originally standing for Control Program/Monitor and later Control Program for Microcomputers, is a mass-market operating system created in 1974 for Intel 8080/ 85-based microcomputers by Gary Kildall of Digital Research, Inc. Initial ...
*
MP/M MP/M (Multi-Programming Monitor Control Program) is a discontinued multi-user version of the CP/M operating system, created by Digital Research developer Tom Rolander in 1979. It allowed multiple users to connect to a single computer, each us ...
*
Concurrent DOS V60 FlexOS is a discontinued modular real-time multiuser multitasking operating system (RTOS) designed for computer-integrated manufacturing, laboratory, retail and financial markets. Developed by Digital Research's Flexible Automation Business U ...
*
FlexOS FlexOS is a discontinued modular real-time multiuser computer multitasking, multitasking operating system (RTOS) designed for computer-integrated manufacturing, laboratory, retail and financial markets. Developed by Digital Research's Flexible ...
*
DR DOS DR-DOS (written as DR DOS, without a hyphen, in versions up to and including 6.0) is a disk operating system for IBM PC compatibles. Upon its introduction in 1988, it was the first DOS attempting to be compatible with IBM PC DOS and MS-DO ...
*
PC DOS PC or pc may refer to: Arts and entertainment * Player character or playable character, a fictional character controlled by a human player, usually in role-playing games or computer games * ''Port Charles'', an American daytime TV soap opera * ...
– IBM's OEM version of (single-user) MS-DOS *
MS-DOS 4.0 (multitasking) MS-DOS 4.0 was a multitasking release of MS-DOS developed by Microsoft based on MS-DOS 2.0. Lack of interest from OEMs, particularly IBM (who previously gave Microsoft multitasking code on IBM PC DOS included with TopView), led to it being rel ...
*
PC-MOS/386 PC-MOS/386 is a multi-user, multitasking computer operating system produced by The Software Link (TSL), announced at COMDEX in November 1986 for February 1987 release. PC-MOS/386, a successor to PC-MOS, can run many MS-DOS programs on the host m ...
– unrelated multitasking DOS clone *
VM/386 VM/386 is a multitasking operating system or 'control program' that took early advantage of the capabilities of Intel's 386 processor. By utilizing Virtual 8086 mode, users were able to run their existing text-based and graphical DOS software i ...
– unrelated multitasking DOS environment *
Virtual DOS machine Virtual DOS machines (VDM) refer to a technology that allows running 16-bit/32-bit DOS and 16-bit Windows programs when there is already another operating system running and controlling the hardware. Overview Virtual DOS machines can operate ei ...
*
Multiuser DOS Federation The Multiuser DOS Federation (MDOS) was an industry alliance to promote the growth and acceptance of multi-user DOS-based solutions on Intel 80286, 286, Intel 80386, 386 and Intel 80486, 486 computers. It was formed in July 1990. Initially among t ...
*
Timeline of operating systems This article presents a timeline of events in the history of computer operating systems from 1951 to the current day. For a narrative explaining the overall developments, see the History of operating systems. 1950s * 1951 ** LEO I 'Lyons Electro ...
*
List of mergers and acquisitions by Citrix Citrix Systems is an American computer software company that was founded in 1989 by Ed Iacobucci. Citrix creates and sells virtualization, cloud computing, networking and SaaS products that aim to provide remote connectivity to workers on a variet ...


References


Further reading

*


External links

* https://web.archive.org/web/20190401161050/http://www.imsltd.com/ former Intelligent Micro Software (IMS) website (vendors of IMS Multiuser DOS, IMS REAL/32, and REAL/NG) * https://web.archive.org/web/20010515195706/http://www.lii.com/ former Logan Industries (LLI) website (IMS REAL/32 US distributor up to 2002-05-01) * https://web.archive.org/web/20071213140207/http://www.conctrls.com/ former Concurrent Controls website (CCI Multiuser DOS) * https://web.archive.org/web/*/https://applica.com Applica, Inc. website * https://web.archive.org/web/20040412051935/http://www.aplycon.com/ former Aplycon Technologies, Inc. website {{Disk operating systems CP/M variants Disk operating systems DOS variants Real-time operating systems Digital Research operating systems Novell operating systems Microcomputer software Discontinued operating systems Proprietary operating systems