FlexOS 186

FlexOS

Company type	Operating system
Industry	Computer software
Predecessor	Concurrent DOS
Founded	1985 in Monterey, California, United States
Headquarters	Monterey, California , United States
Products	FlexOS operating system

FlexOS was a modular, real-time multitasking operating system with multiuser capabilities, developed by Digital Research's Flexible Automation Business Unit in Monterey, California, in 1985. It was designed to serve industries such as computer-integrated manufacturing, laboratories, retail sectors, and financial services.

Conceived as the successor to Digital Research’s earlier Concurrent DOS, FlexOS introduced a fresh modular design and was engineered for portability across various CPU architectures. Initially launched under the names Concurrent DOS 68K and Concurrent DOS 286, it was renamed FlexOS on October 1, 1986, to more clearly define its intended market segments.

Several original equipment manufacturers (OEMs) adopted FlexOS as the core for their proprietary operating systems, including 4680 OS, 4690 OS, and S5-DOS/MT. Meanwhile, the legacy Concurrent DOS architecture continued independently through later versions such as Concurrent DOS XM and Concurrent DOS 386.

Overview

The development of Concurrent DOS 286, Concurrent DOS 68K, and FlexOS was led by Francis "Frank" R. Holsworth (initials FRH). Similar to Portable CP/M, these operating systems were written in the C programming language to enhance hardware portability. They were optimized for low interrupt latency and rapid context switching.

The initial protected mode release of FlexOS 286 version 1.3 targeted Intel 80286 processors, with plans to support NEC V60, NEC V70, and Motorola 68000 CPUs. Executables for FlexOS 286 used the .286 file extension; a CP/M-compatible API front-end enabled support for .CMD files. The .68K extension designated FlexOS 68K binaries derived from Concurrent DOS 68K.

In May 1987, FlexOS version 1.31 became available for systems based on the Intel 80286 architecture. This release required IBM PC/AT-compatible hardware equipped with 640 KB of conventional memory plus 512 KB of extended memory. The system supported dynamically loadable subdrivers for devices such as floppy and hard disks, printers, serial ports, RAM disks, mice, and consoles.

During startup, the FLEX286.SYS kernel loaded resource managers and device drivers defined within a binary CONFIG.SYS configuration file. Its command interpreter (COMMAND.286) ran a CONFIG.BAT batch script instead of AUTOEXEC.BAT. An optional DOS emulator provided partial compatibility with PC DOS 2.1 applications (.COM and .EXE), although some limitations existed due to protected mode operation. Early Intel 80286 processors exhibited bugs that necessitated at least the E2 stepping revision for stable execution.

FlexOS optionally integrated multitasking support for Graphics Environment Manager (GEM) Virtual Device Interface (VDI), enabling graphical application functionality. Version 1.31 could be linked with GEM and also featured support for Novell’s FlexNet networking system.

By June 1987, FlexOS versions targeting the Intel 80386 (host systems) and Intel 80186 (remote controllers) were released; FlexOS 386 introduced windowing capabilities along with compatibility for PC DOS 3.2.

FlexOS versions 2.0 for both the 286 and 386 platforms were officially registered on July 3, 1989.

Key clients during the period of 1990 to 1991 included FANUC, IBM, ICL, Nixdorf, Siemens, Toshiba TEC, Thorn EMI Software, and Micrologic.

In July 1991, Novell acquired Digital Research in an $80 million transaction. Later that year saw the registration of X/GEM for FlexOS version 1.0 alongside FlexNet. FlexOS also functioned as the principal testing environment for Novell Embedded Systems Technology (NEST).

Following Novell’s decision to discontinue development of Digital Research operating systems like Multiuser DOS and Novell DOS, it sold FlexOS in July 1994 to Integrated Systems Inc. (ISI) based in Santa Clara for $3 million—paid half in cash and half in ISI shares representing a two percent stake. ISI continued supporting both FlexOS and its own modular real-time OS pSOS+. By May 1998, FlexOS had reached version 2.33 with plans underway for version 2.34 to enhance support for faster processors, expand memory capacity up to 64 MB, and add compatibility with EIDE and ATAPI CD-ROM drives.

The acquisition of Integrated Systems by competitor Wind River Systems in February 2000 marked the conclusion of further development efforts on both pSOS+ and FlexOS.

Commands

FlexOS offers a wide range of commands designed for system and file operations, including:

• ASSIGN
• BACK
• BACKUP
• BREAK
• CANCEL
• CHDIR
• CHKDSK
• COMMAND
• COMP
• CONFIG
• COPY
• CTTY
• DATE
• DEFINE
• DIR
• DISKCOMP
• DISKCOPY
• DISKSET
• ERASE
• EXIT
• FDISK
• FIND
• FORMAT
• FSET
• LIST
• LOGOFF
• LOGON
• MKDIR
• MORE
• ORDER
• PASSWORD
• PATH
• PRINT
• PROCESS
• PROMPT
• RECDIR
• RECFILE
• RENAME
• RESTORE
• RMDIR
• SECURITY
• SORT
• SYS
• TIME
• TREE
• TYPE
• VER
• VOL

Versions

FlexOS was engineered for several processor architectures, with various editions representing its development milestones:

Motorola 68000 / Freescale/NXP ColdFire MCF5251 series:

• Concurrent DOS 68K versions 1.0 through 1.21 released between 1985 and 1986
• FlexOS 68K series starting with version 1.x

Intel 80286 architecture:

• MP/M-286 introduced in 1982
• Concurrent CP/M-286 and Concurrent DOS 286 lines, including versions from 1.0 to 1.2 during the mid-1980s
• FlexOS 286 editions ranging from version 1.3 in 1986 up to 2.32 by 1993, reflecting continuous improvements

Intel 80186/NEC V20/NEC V30 processors:

• The initial FlexOS 186 release debuted in 1987 following a split in development in 1986

Intel 80386 platform:

• FlexOS 386 introduced in 1987, with updates extending into the late 1990s, including planned releases up to version 2.34 by 1999

NEC V60 system:

• Concurrent DOS V60 variant documented in the early 1990s

These iterations demonstrate FlexOS’s flexibility across different hardware platforms, catering to business environments demanding multitasking and real-time processing.

IBM 4680 OS

IBM selected DR Concurrent DOS 286 as the underlying system for its IBM 4680 operating system, utilized in IBM Plant System products and Point-of-Sale terminals beginning in 1986. The last iteration was Version 4 before the transition to IBM 4690 Version 1.

The releases comprised:

• 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 of 1993, IBM adopted FlexOS version 2.32 as the core for IBM’s first release of the IBM 4690 OS, initially pre-released in September and broadly available by March of the following year. This iteration of FlexOS brought enhancements such as improved memory management, advanced console and pipe features, and superior performance relative to IBM’s prior OS version, IBM 4680 OS Version 4. Additionally, it eliminated restrictions on simultaneous applications through more efficient utilization of KOSPOOL.

IBM rolled out Version 2 of the IBM 4690 OS with support for running Java applications, long filename functionality via a virtual filesystem (VFS), and compatibility with FAT32 storage volumes.

By mid-2005, IBM’s 4690 OS maintained a market share of approximately twelve percent within the POS register/client segment, despite IBM beginning its phase-out process in favor of the IBM Retail Environment for SUSE (IRES).

IBM continued supporting the operating system until April of 2015; the most recent official release from IBM was Version 6 Release 3 in May of 2012. Toshiba carried forward development with subsequent releases: Version 6 Release 4 in January 2014 and Release 5 in January 2016.

Siemens S5-DOS/MT

Siemens incorporated FlexOS technology within their factory automation solutions, particularly in the Simatic S5 STEP-5 operating system known as S5-DOS/MT. This system was constructed on FlexOS 386, integrating components such as X/GEM, FlexNet, and Btrieve. A more compact version, S5-DOS, originated from Digital Research's Personal CP/M-86 platform.

Several Siemens industrial operating systems—including COROS LS-B/FlexOS, COROS OS-B/FlexOS, GRACIS/FlexOS, and OS-525—also utilized FlexOS alongside X/GEM.

FlexOS was offered as an option on Siemens hardware lines like the PC16-20 and PC32 series.

CTM

The shared terminal systems CTM III and CTM IV, deployed by the Japanese postal service, operated on the FlexOS platform.

See also

• Concurrent DOS 286
• GEM
• IBM 4683
• IBM 4690 OS
• IBM 4694
• pSOS
• Distributed Data Management Architecture (DDM)
• Electronic point of sale (EPOS)

Further reading

• Concurrent DOS 286, FlexOS, IBM 4690