FlexOS is a discontinued modular real-time multiuser multitasking operating system (

RTOS A real-time operating system (RTOS) is an operating system (OS) for real-time computing applications that processes data and events that have critically defined time constraints. A RTOS is distinct from a time-sharing operating system, such as Unix ...

) designed for computer-integrated manufacturing, laboratory, retail and financial markets. Developed by

Digital Research Digital Research, Inc. (DR or DRI) was a privately held American software 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 ...

's Flexible Automation Business Unit in

Monterey Monterey ( ; ) is a city situated on the southern edge of Monterey Bay, on the Central Coast of California. Located in Monterey County, the city occupies a land area of and recorded a population of 30,218 in the 2020 census. The city was fou ...

, California, in 1985. The system was considered to become a successor of Digital Research's earlier

Concurrent DOS 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 ...

, but with a new, modular, and considerably different system architecture and portability across several processor families. Still named

Concurrent DOS 68K 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 ...

and

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 ...

, it was renamed into FlexOS on 1 October 1986 to better differentiate the target audiences. FlexOS was licensed by several OEMs who selected it as the basis for their own operating systems like

4680 OS 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 ...

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. ...

S5-DOS/MT 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 ...

and others. Unrelated to FlexOS, the original Concurrent DOS system architecture found a continuation in successors like

Concurrent DOS XM 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 386 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 ...

as well.

Overview

Concurrent DOS 286, Concurrent DOS 68K and FlexOS were designed by 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 mecha ...

FRH). Like

Portable 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. CP/M is ...

and

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 was written in C for higher portability across hardware platforms, and it featured very low interrupt latency and fast context switching. The original

protected mode In computing, protected mode, also called protected virtual address mode, is an operational mode of x86-compatible central processing units (CPUs). It allows system software to use features such as Memory_segmentation, segmentation, virtual mem ...

FlexOS 286 version 1.3 was designed for host machines equipped with 286 CPUs, and with adaptations for NEC V60,

NEC V70 The NEC V60 is a CISC microprocessor manufactured by NEC starting in 1986. Several improved versions were introduced with the same instruction set architecture (ISA), the V70 in 1987, and the V80 and AFPP in 1989. They were succeeded by the V80 ...

and

Motorola 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 ...

processors planned. FlexOS 286 executables using the system's native INT DCh ( INT 220)

application program interface An application programming interface (API) is a connection between computers or between computer programs. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how to build su ...

had the filename extension .286. A

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/Intel 8085, 85-based microcomputers by Gary Kildall of Digital Research, Dig ...

API front-end In software development, frontend refers to the presentation layer that users interact with, while backend involves the data management and processing behind the scenes, and full-stack development refers to mastering both. In the client–server m ...

(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

as of 1986.) In May 1987, FlexOS version 1.31 was released for 80286 machines. The developer version required an

IBM PC/AT The IBM Personal Computer AT (model 5170, abbreviated as IBM AT or PC/AT) was released in 1984 as the fourth model in the IBM Personal Computer line, following the IBM PC/XT and its IBM Portable PC variant. It was designed around the Intel 8028 ...

-compatible machine with 640 KB of conventional and 512 KB of

extended memory In DOS memory management, extended memory refers to memory above the first megabyte (220 bytes) of address space in an IBM PC or compatible with an 80286 or later processor. The term is mainly used under the DOS and Windows operating systems. D ...

, 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 DOS (, ) is a family of disk-based operating systems for IBM PC compatible computers. The DOS family primarily consists of IBM PC DOS and a rebranded version, Microsoft's MS-DOS, both of which were introduced in 1981. Later compatible syste ...

), and its shell (COMMAND.286) would execute a CONFIG.BAT startup batch job instead of the common

AUTOEXEC.BAT AUTOEXEC.BAT is a system file that was originally on DOS-type operating systems. It is a plain-text batch file in the root directory of the boot device. The name of the file is an abbreviation of "automatic execution", which describes its func ...

. FlexOS's optional DOS emulator provided limited PC DOS 2.1 compatibility for DOS .COM and .EXE programs. Certain restrictions applied in " 8086 emulation mode" 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 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 ''descri ...

). These problems had already caused delays in the delivery of Concurrent DOS 286 earlier. IBM PC GEM

The system optionally supported a multitasking GEM VDI for graphical applications. 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. Among the major FlexOS customers in 1990/1991 were

FANUC FANUC ( or ; often styled Fanuc) is a Japanese group of companies that provide automation products and services such as robotics and computer numerical control wireless systems. These companies are principally of Japan, Fanuc America Corpora ...

IBM International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American Multinational corporation, multinational technology company headquartered in Armonk, New York, and present in over 175 countries. It is ...

, ICL, Nixdorf,

Siemens Siemens AG ( ) is a German multinational technology conglomerate. It is focused on industrial automation, building automation, rail transport and health technology. Siemens is the largest engineering company in Europe, and holds the positi ...

, TEC,

Thorn EMI Software IBM has undergone a large number of mergers and acquisitions during a corporate history lasting over a century; the company has also produced a number of spinoffs during that time. The acquisition date listed is the date of the agreement betwe ...

and Micrologic.

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 NetWare. Novell technolog ...

bought Digital Research for million in July 1991. '' X/GEM for FlexOS release 1.0'' (a.k.a. X/GEM FlexOS 286 and 386) and FlexNet were registered on 21 December 1992. FlexOS was used as the primary test platform for the new

Novell Embedded Systems Technology Novell Embedded Systems Technology (NEST) was a series of application programming interface, APIs, data formats and network protocol stacks written in a highly portable fashion intended to be used in embedded systems. The idea was to allow vario ...

(NEST). When Novell decided to abandon further development of the various Digital Research operating systems such as

Multiuser DOS 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 ...

(a successor to Concurrent DOS) and

Novell DOS DR-DOS is a disk operating system for IBM PC compatibles, originally developed by Gary A. Kildall's Digital Research, Inc. and derived from Concurrent PC DOS 6.0, which was an advanced successor of CP/M-86. Upon its introduction in 1988, ...

(a successor to

DR DOS DR-DOS is a disk operating system for IBM PC compatibles, originally developed by Gary A. Kildall's Digital Research, Inc. and derived from Concurrent PC DOS 6.0, which was an advanced successor of CP/M-86. Upon its introduction in 1988, ...

), they sold FlexOS off to the Santa Clara, California-based Integrated Systems Inc. (ISI) for million 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. Integrated Systems was bought by their competitor

Wind River Systems Wind River Systems, Inc., also known as Wind River (trademarked as Wndrvr), is an Alameda, California–based company, subsidiary of Aptiv PLC. The company develops embedded system and cloud software consisting of real-time operating systems sof ...

in February 2000.

Commands

The following list of commands is supported by FlexOS: * ASSIGN * BACK *

BACKUP In information technology, a backup, or data backup is a copy of computer data taken and stored elsewhere so that it may be used to restore the original after a data loss event. The verb form, referring to the process of doing so, is "wikt:back ...

BREAK Break or Breaks or The Break may refer to: Time off from duties * Recess (break), time in which a group of people is temporarily dismissed from its duties * Break (work), time off during a shift/recess ** Coffee break, a short mid-morning rest ...

* CANCEL * CHDIR *

CHKDSK In computing, CHKDSK (short for "check disk") is a system software, system tool and command (computing), command in DOS and Microsoft Windows (and related operating systems), as well as Digital Research FlexOS, IBM/Toshiba 4690 Operating System, 4 ...

COMMAND Command may refer to: Computing * Command (computing), a statement in a computer language * command (Unix), a Unix command * COMMAND.COM, the default operating system shell and command-line interpreter for DOS * Command key, a modifier key on A ...

COMP Comp, COMP or Comps may refer to: Places In England: * Comp, Kent In France: * Comps, Drôme * Comps, Gard * Comps, Gironde * Comps-la-Grand-Ville * Comps-sur-Artuby Music *Accompaniment, especially in jazz ** Comping (jazz) *Compilatio ...

* CONFIG * COPY * CTTY * DATE * DEFINE * DIR * DISKCOMP *

DISKCOPY In computing, diskcopy is a command used on a number of operating systems for copying the complete contents of a diskette to another diskette. Implementations The command is available in MS-DOS, IBM PC DOS, DR FlexOS, IBM/Toshiba 4690 OS, Me ...

* DISKSET * ERASE *

EXIT Exit(s) may refer to: Architecture and engineering * Door * Portal (architecture), an opening in the walls of a structure * Emergency exit * Overwing exit, a type of emergency exit on an airplane * Exit ramp, a feature of a road interchange A ...

FDISK fdisk is a command-line utility for disk partitioning. It has been part of DOS, DR FlexOS, IBM OS/2, and early versions of Microsoft Windows, as well as certain ports of FreeBSD, NetBSD, OpenBSD, DragonFly BSD and macOS for compatibilit ...

* FIND * FORMAT * FSET * LIST * LOGOFF * LOGON *

MKDIR (make directory) command (computing), command in the Unix, DOS, Digital Research, DR FlexOS, IBM OS/2, Microsoft Windows, and ReactOS operating systems is used to make a new directory (file systems), directory. It is also available in the Unified ...

* MORE * ORDER * PASSWORD *

PATH A path is a route for physical travel – see Trail. Path or PATH may also refer to: Physical paths of different types * Bicycle path * Bridle path, used by people on horseback * Course (navigation), the intended path of a vehicle * Desir ...

* PRINT * PROCESS * PROMPT * RECDIR * RECFILE * RENAME * RESTORE *

RMDIR In computing, rmdir (or rd) is a command which will remove an empty directory on various operating systems. Implementations The command is available in Unix (e.g. macOS, Solaris, AIX, HP-UX), Unix-like (e.g. FreeBSD, Linux), DOS, Digital ...

* SECURITY *

SORT Sort may refer to: * Sorting, any process of arranging items in sequence or in sets ** Sorting algorithm, any algorithm for ordering a list of elements ** Mainframe sort merge, sort utility for IBM mainframe systems ** Sort (Unix), which sorts the ...

* SYS *

TIME Time is the continuous progression of existence that occurs in an apparently irreversible process, irreversible succession from the past, through the present, and into the future. It is a component quantity of various measurements used to sequ ...

TREE In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, e.g., including only woody plants with secondary growth, only ...

TYPE Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * ...

VER Ver or VER may refer to: * Voluntary Export Restraints, in international trade * VER, the IATA airport code for Veracruz International Airport * Volk's Electric Railway, Brighton, England * VerPublishing, of the German group VDM Publishing, re ...

* VOL

Versions

Known FlexOS versions include:

Freescale Freescale Semiconductor, Inc. was an American semiconductor manufacturer. It was created by the divestiture of the Semiconductor Products Sector of Motorola in 2004. Freescale focused their integrated circuit products on the automotive, embedde ...

/ NXP ColdFire MCF5251 platform: *

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 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 f ...

platform: * MP/M-286 (1982) * Concurrent CP/M-286 (1985) *

preview (1985-01) *

1.0 (1985-08-06) ** Concurrent DOS 286 1.0.01 (1985-08-18/1985-08-21) ** Concurrent DOS 286 1.0.02 (1985-08-22/1985-09-12) ** Concurrent DOS 286 1.0.03 (1985-09-10/1985-09-12) ** Concurrent DOS 286 1.0.04 (1985-09-17) ** Concurrent DOS 286 1.0.05 (1985-11-01) ** Concurrent DOS 286 1.0.06 (1985-12-10) * Concurrent DOS 286 1.1 (1986-01-07) * Concurrent DOS 286 1.2 (1986) ** Concurrent DOS 286 1.2.00 (1986-04-10/1986-04-24) ** Concurrent DOS 286 1.2.01 (1986-04-16/1986-05-19) ** Concurrent DOS 286 1.2.02 (1986-08-18) * FlexOS 286 1.3 (November 1986) * FlexOS 286 1.31 (May 1987) * FlexOS 286 1.5 (1988-02-29) * FlexOS 286 2.0.00 (1988-03-31) * FlexOS 286 2.0 (July 1989) * FlexOS 286 2.32 (July 1993)

Intel 80186 The Intel 80186, also known as the iAPX 186, or just 186, is a microprocessor and microcontroller introduced in 1982. It was based on the Intel 8086 and, like it, had a 16-bit external Bus (computing)#Address bus, data bus multiplexed with a 20 ...

NEC V20 The NEC V20 is a microprocessor that was designed and produced by NEC. It is both pin compatible and object-code compatible with the Intel 8088, with an instruction set architecture (ISA) similar to that of the Intel 80188 with some extensio ...

/ V30 platform: * FlexOS 186 (1986-09-04 forked) * FlexOS 186 1.0 (June 1987)

Intel 80386 The Intel 386, originally released as the 80386 and later renamed i386, is the third-generation x86 architecture microprocessor from Intel. It was the first 32-bit computing, 32-bit processor in the line, making it a significant evolution in ...

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: *

Adaptations

IBM 4680 OS

Named IBM 4680 OS Version 1,

originally chose DR Concurrent DOS 286 as the basis of their ''IBM 4680'' computer for IBM Plant System products and

Point-of-Sale The point of sale (POS) or point of purchase (POP) is the time and place at which a retail transaction is completed. At the point of sale, the merchant calculates the amount owed by the customer, indicates that amount, may prepare an invoice f ...

terminals in 1986. The last release of the IBM 4680 OS has been Version 4, before it was replaced by IBM 4690 Version 1. Versions: * 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. To support

Java Java is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea (a part of Pacific Ocean) to the north. With a population of 156.9 million people (including Madura) in mid 2024, proje ...

, IBM 4690 OS Version 2 added support for

long filename Long filename (LFN) support is Microsoft's backward-compatible extension of the 8.3 filename (short filename) naming scheme used in MS-DOS. Long filenames can be more descriptive, including longer filename extensions such as .jpeg, .tiff, an ...

s by means of a

virtual filesystem A virtual file system (VFS) or virtual filesystem switch is an abstract layer on top of a more concrete file system. The purpose of a VFS is to allow client applications to access different types of concrete file systems in a uniform way. A VFS ...

(VFS) architecture and it introduced

FAT32 File Allocation Table (FAT) is a file system developed for personal computers and was the default file system for the MS-DOS and Windows 9x operating systems. Originally developed in 1977 for use on floppy disks, it was adapted for use on ...

volumes. 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 IBM Retail Store Solutions was IBM International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American Multinational corporation, multinational technology company headquartered in Armonk, New York, and p ...

(IRES). IBM continued 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. Toshiba released Toshiba 4690 OS Version 6 Release 4 in January 2014 and Version 6 Release 5 in January 2016.

Siemens S5-DOS/MT

used and still maintains FlexOS in their factory automation equipment as well. For example, their Simatic S5 STEP-5 operating system

is based on FlexOS 386 with X/GEM, FlexNet and

Btrieve Btrieve is a transactional database ( navigational database) software product. It is based on Indexed Sequential Access Method (ISAM), which is a way of storing data for fast retrieval. There have been several versions of the product for DOS, Linux ...

, 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, OS-525 were FlexOS and X/GEM-based. Computers such as the PC 16-20 and the PC 32 series were available with FlexOS as well.

CTM

The Japanese post office shared terminals III and CTM IV were based on FlexOS.