|Latest release||2.33 / 1998-05|
|Latest preview||2.34 / 1999|
|Marketing target||Industrial, PoS|
|Platforms||80186, 80286, 80386, 68000, V60, V70|
|Default user interface||various frontends, X/GEM|
|Preceded by||Concurrent DOS 286, Concurrent DOS 68K, Concurrent DOS V60|
|Succeeded by||S5-DOS/MT, 4680 OS, 4690 OS|
FlexOS is a discontinued modular real-time multi-user multi-tasking operating system (RTOS) designed for computer-integrated manufacturing, laboratory, retail and financial markets. It was developed by Digital Research's Flexible Automation Business Unit in Monterey, California since November 1986 and was marketed since January 1987 as a reengineered continuation of Digital Research's Concurrent DOS 286 multiuser multitasking operating system.
Like Portable CP/M, Concurrent DOS 286, Concurrent DOS 68K and Concurrent DOS V60, FlexOS was written in C for higher portability across hardware platforms, and it featured very low interrupt latency and fast context switching. It is supported by popular SSL/TLS libraries such as wolfSSL.
The original protected mode FlexOS 286 version 1.3 was designed for host machines equipped with 286 CPUs, and with adaptations for NEC V60, NEC V70 and Motorola 68000 processors planned. FlexOS 286 executables using the system's native INT DCh (INT 220) application program interface had the filename extension .286. A CP/M API front end (FE) was available as well, using the extension .CMD for executables. (A filename extension of .68K was reserved for FlexOS 68K, a file extension derived from Concurrent DOS 68K as of 1986.)
In May 1987, FlexOS version 1.31 was released for 80286 machines. The developer version required an IBM PC/AT-compatible machine with 640 KB of conventional and 512 KB of extended memory, and either a (monochrome) CGA or an EGA graphics adapter.
FlexOS supported a concept of dynamically loadable and unloadable subdrivers, and it came with driver prototypes for floppies, hard disks, printers, serial interfaces, RAM disks, mice and console drivers.
During boot, the FLEX286.SYS kernel would load the resource managers and device drivers specified in the CONFIG.SYS binary file (not to be mixed up with the similarly named CONFIG.SYS configuration file under DOS), and its shell (COMMAND.286) would execute a CONFIG.BAT startup batch job instead of the common AUTOEXEC.BAT.
FlexOS's optional DOS emulator provided limited PC DOS 2.1 compatibility for DOS .COM and .EXE programs. Certain restrictions applied since these programs were executed in the processor's protected mode. Due to bugs in earlier steppings of the Intel 80286, the FlexOS 286 DOS front-end required at least the 80286 E2 stepping to function properly (see LOADALL). These problems had already caused delays in the delivery of Concurrent DOS 286 earlier.
FlexOS 1.31 could be linked with none, either or both of these two modules. FlexOS 1.31 also supported FlexNet.
By June 1987 there were also versions 1.0 of FlexOS 386 (for hosts) and FlexOS 186 (for remote cell controllers). FlexOS 386 provided a windowing feature, and offered PC DOS 3.2 and GEM compatibility.
FlexOS 286 and FlexOS 386 versions 2.0 were registered on 3 July 1989.
X/GEM for FlexOS release 1.0 (a.k.a. X/GEM FlexOS 286 and 386) and FlexNet were registered on 21 December 1992.
When Novell decided to abandon further development of the various Digital Research operating systems such as Multiuser DOS (a successor to Concurrent DOS) and Novell DOS (a successor to DR DOS), they sold FlexOS off to the Santa Clara, California-based Integrated Systems, Inc. (ISI) for US$3,000,000 in July 1994. The deal comprised a direct payment of half this sum as well as shares representing 2% of the company. The company already had pSOS+, another modular real-time multitasking operating system for embedded systems, but they continued to maintain FlexOS as well. FlexOS version 2.33 was current as of May 1998 and with FlexOS 2.34 to be released soon after with added support for faster CPUs, 64 MB of memory, EIDE and ATAPI CDROM drives.
Known FlexOS 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)
- FlexOS 68K 1.x?
Intel 80286 platform:
- Concurrent DOS 286 1.0 (1985)
- Concurrent DOS 286 1.1 (1986-01-07)
- Concurrent DOS 286 1.2 (1986)
- FlexOS 286 1.3 (November 1986)
- FlexOS 286 1.31 (May 1987)
- FlexOS 286 2.0 (July 1989)
- FlexOS 286 2.32 (July 1993)
- FlexOS 186 1.0 (June 1987)
Intel 80386 platform:
- FlexOS 386 1.0 (June 1987)
- FlexOS 386 2.0 (July 1989)
- FlexOS 386 2.30?
- FlexOS 386 2.31?
- FlexOS 386 2.32 (July 1993)
- FlexOS 386 2.33 (May 1998)
- FlexOS 386 2.34 (planned for 1999)
NEC V60 platform:
IBM 4680 OS
Named IBM 4680 OS Version 1, IBM originally chose DR Concurrent DOS 286 as the basis of their IBM 4680 computer for IBM Plant System products and Point-of-Sale terminals in 1986. The last release of the IBM 4680 OS has been Version 4, before it was replaced by IBM 4690 Version 1.
- IBM 4680 Operating System Version 1 Release 1
- IBM 4680 Operating System Version 1 Release 2
- IBM 4680 Operating System Version 1 Release 3
- IBM 4680 Operating System Version 2 Release 1
- IBM 4680 Operating System Version 3 Release 1
- IBM 4680 Operating System Version 4 Release 1
IBM and Toshiba 4690 OS
In July 1993, IBM announced the adoption of FlexOS version 2.32 as the basis of their IBM 4690 OS Version 1, to be pre-released on 24 September 1993 and generally made available from 25 March 1994. FlexOS 2.32 supported 286 and 386 modes, had more efficient memory management, better console and pipe systems, and brought overall quality and performance improvements compared to the version that came with IBM 4680 OS Version 4. Further, it removed limits on the number of applications running concurrently due to its more efficient use of KOSPOOL.
According to "The Year of the Store?", IHL Consulting Group/RIS News, IBM 4690 OS still had a market share of 12% in the POS register/client market in June 2005, when IBM was starting to phase it out in favour to IBM Retail Environment for SUSE (IRES).
IBM will continue to maintain 4690 OS up to April 2015, with the most recent version released by IBM in May 2012 being IBM 4690 OS Version 6 Release 3.
Meanwhile, Toshiba has released Toshiba 4690 OS Version 6 Release 4 in January 2014.
Siemens used and still maintains FlexOS in their factory automation equipment as well. For example, their Simatic S5 STEP-5 operating system S5-DOS/MT is based on FlexOS 386 with X/GEM, FlexNet and Btrieve, whereas the smaller S5-DOS system, also present on these systems, is a variant of Digital Research's Personal CP/M-86.
Siemens industrial systems like COROS LS-B/FlexOS, COROS OS-B/FlexOS, GRACIS/FlexOS, Teleperm M OS-525 were FlexOS and X/GEM-based.
Computers such as the Sicomp PC 16-20 and the PC 32 series were available with FlexOS as well.
The Japanese post office shared terminals CTM III and CTM IV were based on FlexOS.
- Concurrent DOS 286
- IBM 4683
- IBM 4690 OS
- IBM 4694
- Distributed Data Management Architecture (DDM)
- Electronic point of sale (EPOS)
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This is a guide to the operation of the High C compiler as implemented for the Concurrent DOS 286 1.2 or later operating system - hereafter abbreviated to just "Concurrent" per Digital Research custom - running on the Intel 80286 microprocessor and using the Intel Object-Module Format (OMF). The compiler generates code for any of the Intel 8086/88/186/188/286 family of microprocessors.
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- FlexOS Programmer's Guide Version 1.3 (PDF). 1.3 (1 ed.). Digital Research, Inc. November 1986. 1073-2023-001. Retrieved 2018-09-14.
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- FlexNet Network Operating System User's Guide (PDF). 1.3 (1 ed.). Digital Research, Inc. November 1986. 1082-2003-001. Retrieved 2018-09-14.
- Concurrent DOS 286, FlexOS, IBM 4690