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Digital Research, Inc.
Company typePrivate
IndustrySoftware
Founded1976; 50 years ago (1976)
FounderGary A. Kildall
Headquarters
Pacific Grove, California
,
United States
ProductsDR-DOS, CP/M-86, Concurrent DOS, DOS Plus, Multiuser DOS, PalmDOS

DR-DOS (styled as DR DOS without a hyphen until version 6.0) is a disk operating system designed for IBM PC-compatible computers. It was initially created by Digital Research, Inc., founded by Gary A. Kildall, and evolved from Concurrent PC DOS 6.0, itself a sophisticated successor to CP/M-86. Launched in 1988, DR-DOS was the first DOS variant explicitly developed to be compatible with both IBM PC DOS and MS-DOS.

The debut version was 3.31, matching the version numbering used by MS-DOS at that time. The first retail edition, DR DOS 5.0, appeared in 1990 and earned widespread praise, quickly becoming the main rival to Microsoft's MS-DOS, which released its own version 5.0 more than a year afterward. DR-DOS also introduced ViewMAX, a graphical user interface layer.

Following this, DR DOS 6.0 was released in 1991. After Digital Research was acquired by Novell, the subsequent version was renamed Novell DOS 7.0 in 1994. Later ownership by Caldera resulted in updated editions, some of which were partially open-source and marketed under the Caldera brand and briefly as OpenDOS. The final desktop release, Caldera DR-DOS 7.03, came out in 1999 before the focus shifted toward embedded system applications under Caldera and later DeviceLogics.

CP/M Origins

Digital Research originally developed CP/M for 8-bit processors such as the Intel 8080 and Zilog Z80, eventually creating CP/M-86 for the Intel 8086/Intel 8088 architecture. Since its introduction in the mid-1970s, CP/M was widely adopted and bundled with many non-proprietary personal computers. However, the arrival of the IBM PC in 1981 transformed the landscape.

In 1980, IBM initially sought Digital Research’s assistance to develop an x86 variant of CP/M but withdrew due to contractual disagreements. Subsequently, IBM collaborated with Microsoft, which had acquired 86-DOS from Seattle Computer Products (SCP). This product evolved into Microsoft’s MS-DOS and IBM’s PC DOS. The design of 86-DOS closely mirrored the command structure and API of CP/M 2.2. Digital Research threatened to take legal action over alleged infringement. By early 1982, IBM agreed to offer Digital Research's CP/M-86 alongside PC DOS. However, CP/M-86's $240 price tag compared to PC DOS's significantly lower cost limited its market success despite having better initial software availability.

Digital Research faced challenges competing against the dominant Microsoft-IBM software ecosystem and adapted its multitasking successors (MP/M-86, Concurrent CP/M-86) to support MS-DOS applications. This capability was publicly demonstrated in December 1983 and released as Concurrent DOS 3.1 (CDOS with BDOS 3.1) in March 1984 for hardware manufacturers. Although Concurrent DOS later evolved into products like Multiuser DOS and REAL/32, it remained expensive and less practical for single-user desktop environments.

To provide a more streamlined solution, Digital Research introduced versions of DOS Plus from 1.0 through 2.1 in 1985—a simplified single-user offshoot of Concurrent DOS that supported multitasking and offered limited compatibility with DOS software. Seeking enhanced DOS compatibility, Digital Research launched a native DOS product in 1988 known as DR DOS.

While based in Pacific Grove and later Monterey, California, development of DOS Plus began at Digital Research Europe’s OEM Support Group located in Newbury, Berkshire, UK since 1983. From 1986 onward, most development efforts on Concurrent DOS 386/XM, Multiuser DOS, DR DOS, and PalmDOS were conducted at Digital Research’s European Development Centre in Hungerford, Berkshire, with additional input from Digital Research GmbH in Munich, Germany.

Initial DR DOS Release

In 1987, responding to demands from OEM partners, Digital Research initiated development of a new DOS variant to overcome the shortcomings of MS-DOS. A pivotal multi-million dollar agreement with Kazuhiko "Kay" Nishi of ASCII Corporation facilitated entry into the Japanese OEM sector. The inaugural DR DOS edition was officially released on May 28, 1988.

The versioning scheme corresponded with MS-DOS feature sets; the first public iteration was DR DOS 3.31, matching Compaq MS-DOS 3.31 in functionality, including support for large disks via FAT16B ("BIGDOS"). Externally, DR DOS 3.31 identified itself as "IBM PC DOS 3.31," while internally its BDOS kernel was labeled version 6.0, reflecting its origin from Concurrent DOS 6.0 but without multitasking and multiuser capabilities. An IBM-compatible DOS-BIOS replaced the original XIOS component. Core system files comprised DRBIOS.SYS (DOS-BIOS) and DRBDOS.SYS (BDOS kernel), with the OEM disk marked "DIGITAL␠".

Enhanced command-line utilities characterized DR DOS, featuring integrated help, detailed error reporting, sophisticated command history and editing via the HISTORY directive, and native file and directory password protection at the kernel level. Licensing costs were lower than those of MS-DOS, and from inception, it was engineered for ROM embedding—the ROM-based variant was named ROS (ROM Operating System). This attracted PC manufacturers’ interest, prompting several system upgrades.

During this period, MS-DOS was exclusively distributed bundled with hardware to OEMs, so DR DOS gained market presence by being available through retail channels starting with version 3.4x.

Documented releases include DR DOS 3.31 (BDOS 6.0, June 1988, OEM only), followed by versions 3.32 (August 17, 1988), 3.33 (September 1, 1988), 3.34, 3.35 (October 21, 1988), 3.40 (January 25, 1989), and 3.41 (BDOS 6.3, June 1989, available both OEM and retail). Most versions had multiple hardware-specific variants. While the majority of OEMs maintained the DR DOS branding, 2001 Sales, Inc. marketed it under the name EZ-DOS 3.41 (also referred to as EZ-DOS 4.1).


DR DOS Version 5.0

Released in May 1990 under the codename "Leopard," DR DOS 5.0 preserved compatibility by identifying itself as "PC DOS 3.31" externally while internally operating on a single-user BDOS kernel version 6.4. The version number skipped “4” to avoid association with the poorly received MS-DOS 4.0 release. This edition introduced ViewMAX, a GEM-based graphical file management shell carrying the tagline "Digital Research - We make computers work".

Business-centric enhancements included the patented BatteryMAX power-saving system, bundled disk caching software named DRCACHE, a remote file transfer utility called FILELINK, a cursor customization tool (CURSOR), and an upgraded memory manager known as MemoryMAX. System filenames were changed to IBMBIO.COM and IBMDOS.COM, accompanied by an advanced boot loader that provided flexible disk loading options. The OEM identification was updated to "IBM␠␠3.3".


DR DOS 5.0 broke new ground by implementing load-high functionality that moved both the kernel and disk buffers into the High Memory Area (HMA), thereby freeing precious conventional memory—the first 640 KB segment where DOS applications execute.[1] On systems based on the Intel 80386 processor, its EMS memory manager allowed device drivers to be loaded into upper memory blocks, further increasing available base memory.

This built-in solution surpassed third-party utilities like QEMM, enabling DR DOS users to access substantially more free conventional memory on both Intel 286 and 386 platforms. While typical MS-DOS setups offered only about 300–400 KB free after loading essential drivers, DR DOS 5.0 could preserve up to approximately 620 KB for application use with minimal manual tuning. Additionally, employing MEMMAX +V extended conventional memory into unused video RAM areas, adding another estimated 64–96 KB.

However, this surplus of free conventional memory occasionally led to compatibility problems with legacy software that depended on address wrapping methods for operation stability. To mitigate this issue, DR DOS 5.0 introduced the MEMMAX -L parameter which pre-allocates low-address memory regions to guarantee proper program loading above this threshold—trading off some conventional memory capacity in favor of compatibility reliability. By default, MEMMAX was configured with +L to optimize available application memory.



DR DOS 6.0 / Rivalry with Microsoft

In response to fierce rivalry, Microsoft unveiled MS-DOS 5.0 in May 1990 and launched it in June 1991, incorporating features akin to those found in DR DOS, notably enhanced memory management capabilities.

Digital Research introduced DR DOS 6.0 ("Buxton") in September 1991, internally designated BDOS version 6.7 but identifying itself as "IBM PC DOS 3.31" for compatibility reasons. This release included SuperStor disk compression to optimize hard disk utilization and added file deletion tracking along with undelete utilities developed by Roger A. Gross.

The release featured TASKMAX, a task-switching utility compliant with the industry-standard API, enabling multiple programs to run by suspending background processes until they were brought to the foreground. TASKMAX utilized XMS memory on 286 or higher processors and provided basic Copy & Paste functionality. Graphical user interfaces such as ViewMAX or PC/GEOS could incorporate TASKMAX’s menu system, allowing task switching within a GUI environment.

Microsoft countered with MS-DOS 6.0, integrating comparable features.

In December 1991, a Windows 3.1 pre-release contained the AARD code, which detected non-Microsoft DOS versions through a non-critical error message. Digital Research issued a patch for DR DOS 6.0 within six weeks that circumvented this detection without impairing functionality, releasing it as the "business update." After disabling the check, Windows operated smoothly on DR DOS and Novell DOS platforms.

By July 1992, Digital Research Japan delivered DR DOS 6.0/V, a version compatible with Japanese DOS/V, alongside a Korean edition.

PalmDOS

In 1992, following Novell’s acquisition of Digital Research in July 1991, a derivative product codenamed "Merlin" was launched as NetWare PalmDOS 1. This lightweight variant of DR DOS 6.0 targeted emerging palmtop and personal digital assistant devices.

PalmDOS was the first to implement the BDOS 7.0 kernel featuring native DOS-compatible internal data structures, enhancing application compatibility while minimizing kernel size—an essential factor for PDA hardware. It introduced an authentic Current Directory Structure (CDS), restricting directory path lengths to 66 characters, unlike earlier DR DOS editions. To preserve kernel compactness and ensure Windows compatibility, PalmDOS identified itself as "PC DOS 3.31" to software.

Engineered for execution from ROM, PalmDOS supported PCMCIA cards via DPMS and incorporated power management tools such as BatteryMAX and the patented dynamic idle detection driver $IDLE$. It also provided MINIMAX task switching for Personal Information Modules (PIM) running directly from ROM through Execute-In-Place (XIP). The PCMCIA stack development involved contributions from Ian H. S. Cullimore, a prominent figure in the PCMCIA/PC Card industry.

Novell DOS 7 / Novell’s Enhancements

Novell DOS was the brand name adopted by Novell Corporation for DR DOS after acquiring Digital Research in 1991. It consistently outperformed MS-DOS in terms of features and efficiency, with Novell DOS 7 released in 1993 surpassing competitors like PC DOS 6.1 and MS-DOS 6.2.

Under CEO Robert J. Frankenberg’s direction, Novell aggressively streamlined its portfolio by divesting products such as Btrieve and discontinuing Novell DOS along with certain WordPerfect multimedia offerings. The company licensed technology from Stac Electronics for use in Novell DOS and its network operating system NetWare. In July 1996, Novell sold the DR DOS product line to Caldera, which sought an operating system to bundle with its OpenLinux distribution.

Internally called "Panther," DR DOS 7.0 experienced delays amid Novell’s broader strategy aimed at challenging Microsoft’s market dominance through investments in Unix and acquisitions of WordPerfect and Borland software products. Planned enhancements included Unix-style multi-user security features and new graphical interfaces (ViewMAX 3 and "Star Trek," an Apple System 7 port), though these were not present when Novell DOS 7 officially launched in December 1993.

Despite being larger and missing some anticipated features, many experts considered Novell DOS 7 the most advanced DOS version available at that time. In Germany, an aggressive marketing campaign aimed at capturing a 20% market share resulted in approximately 1.5 million units sold by early 1994 via OEMs, mail order, and retail channels.

A significant feature was Personal NetWare (PNW), Novell’s enhanced peer-to-peer networking solution succeeding NetWare Lite. However, its incompatibility with Microsoft’s increasingly popular networking protocols—used by Windows for Workgroups, OS/2, and Windows NT—limited its adoption.

Novell DOS 7 incorporated the DOSMGR API alongside the BDOS 7.2 kernel reporting itself as DOS version 6.0 (OEM ID "IBM") to maintain compatibility with Windows environments. It introduced sophisticated memory management supporting both DPMI and DPMS standards along with versatile loadhigh options.

A notable innovation was true preemptive multitasking of multiple DOS applications within virtual DOS machines (VDMs) via MultiMAX technology—comparable to Multiuser DOS but fully compatible with native DOS without requiring a GUI interface. TASKMGR managed tasks similarly to DR DOS 6.0’s TASKMAX but could utilize EMM386’s /MULTI switch to enable a native 32-bit protected mode core supporting multitasking, multithreading, hardware virtualization, and domain control of VDMs compatible with Windows systems.

Both Novell DOS 7 and Personal NetWare included NetWars, a network-enabled three-dimensional arcade game.

Although it required numerous bug fixes and never achieved full stability before Microsoft's Chicago (Windows 95) beta release appeared, Novell ceased further development on Novell DOS 7 by September 1994 and concluded maintenance support by January 1996 after delivering over fifteen updates.

Post-Novell Developments

In pursuit of a DOS operating system to bundle with their OpenLinux distribution, Caldera acquired the product line from Novell on July 23, 1996, as Novell no longer saw substantial commercial benefit in maintaining it.

With IBM's PC DOS 6.3 and Caldera’s own DR-DOS as competitors, Microsoft limited Windows 95 compatibility exclusively to its proprietary DOS versions. This practice prompted Caldera, supported by the Canopy Group, to initiate a significant lawsuit. Despite Microsoft's efforts to dismiss the case, it culminated in an out-of-court settlement on January 7, 2000, amounting to $280 million—details of which surfaced in 2009.

In August 1996, Roger A. Gross, one of the original DR-DOS developers, proposed resuming development with an emphasis on Windows 95 compatibility to strengthen the legal claims. Following discussions in Utah, Gross was recruited to launch a UK branch. Subsequently, Caldera UK Ltd. was established in September 1996 near Andover, Hampshire, where a team comprising both original and new engineers began work.

During the next two years, this group introduced several enhancements including a TCP/IP stack sourced from LAN WorkPlace for DOS, a 32-bit protected-mode web browser named DR-WebSpyder (based on Arachne (web browser)), POSIX-compliant Pthreads multitasking capabilities, support for long filenames (LONGNAME), and FAT32 integration (DRFAT32). Andrew Schulman contributed to "WinGlue," a confidential initiative aimed at replacing the MS-DOS 7.xx component within DR-DOS to achieve Windows 95/98 compatibility. This project was showcased at CeBIT in 1998 and evolved into "WinBolt," unreleased builds that played a vital role in litigation efforts.

Caldera UK introduced Caldera OpenDOS 7.01 in February 1997—a rebranded iteration of Novell DOS 7 that lacked recent patches due to missing source code from Novell. Although some utilities included with Novell DOS were omitted, updated tools such as PNUNPACK and Advanced NetWars were part of the package.

In May 1997, select portions of OpenDOS 7.01 were briefly made available under restrictive open-source licenses but were later withdrawn to align with commercial objectives.

After releasing beta versions late in 1997, Caldera launched DR-OpenDOS 7.02 in December of the same year; by March 1998 it was renamed Caldera DR-DOS 7.02. This release (BDOS version 7.3) addressed BIOS and BDOS bugs, enhanced compatibility with Windows 9x—including support for third-party compression utilities like DriveSpace—added a diagnostics mode, improved CONFIG.SYS scripting for boot menus and error handling, and implemented load-high memory management features that increased available conventional memory essential for third-party drivers and shells such as 4DOS.

The update also incorporated an advanced National Language Support framework allowing multiple COUNTRY.SYS files with dynamic parsing compatible with MS-DOS/PC DOS formats. Additional features included adoption of the ISO 8601 date standard and Euro currency support. DR-DOS 7.02 was fully compliant with Year 2000 requirements and featured an updated FDISK utility capable of formatting FAT32 volumes.

The newer BDOS core caused compatibility problems with legacy applications; these were alleviated through improved SETVER functionality that enabled version number masking for enhanced compatibility.

An incompatibility emerged with QEMM 8’s DOS-UP feature due to modifications in file handle chunking; this was addressed via a patch named IBMBIO85.SCR, though it introduced compromises between DOS-UP functionality and Windows 3.xx compatibility.

In August 1998,[2] Caldera established two subsidiaries: Caldera Systems, Inc., dedicated to Linux-based ventures; and Caldera Thin Clients, Inc., focusing on embedded and thin-client technologies.[3]

DR-DOS version 7.03 was initially distributed as a pre-release during Christmas of 1998 and officially launched on January 6, 1999 by Caldera UK. It featured improvements to memory management including enhanced DPMI support, added utilities such as DEVLOAD and DRMOUSE, but introduced a modified FAT OEM label which caused cross-platform interoperability issues that could be circumvented.

This release marked the final desktop-oriented version.

Following Roger Gross’s departure in early 1999, Caldera relocated DR-DOS development back to the United States; lacking sufficient expertise domestically led to the closure of the UK division.[4] The DR-DOS product line was transferred under Caldera Thin Clients—renamed Lineo, Inc., in July 1999.[5] Lineo reissued DR-DOS 7.03 under the "Caldera DR-DOS" brand but shifted focus primarily towards embedded Linux solutions via Embedix.

Subsequent standalone releases included OEM-specific DR-DOS versions 7.04 (August 1999) and 7.05 (November 1999), featuring streamlined kernels with native FAT32 and large disk support utilized by tools such as Ontrack's Easy Recovery and Seagate's SeaTools diagnostics.[6][7] Internally reported as BDOS version 7.3 yet externally identified as "PC DOS 7.10" to highlight FAT32 integration enhancements.

Kernels from versions 7.04/7.05 could be combined with earlier modules enabling LBA drive support beyond the traditional 8 GB limit.

The December 1999 release of version 7.06 consolidated kernel files into a single executable compatible with MS-DOS 7.10 boot sectors but not those specific to DR-DOS.[8]

Version 7.07 introduced new bootstrap loaders supporting CHS/LBA disk access across FAT12/16/32 file systems while unifying bootloader conventions for DR-DOS, PC DOS, MS-DOS, Windows multi-boot environments, REAL/32, and LOADER through a single MBR/boot sector loader called NEWLDR.[8] This advancement facilitated multi-boot configurations while preserving backward compatibility down to DR-DOS version 3.31.

In summary, Caldera’s approach transitioned from revitalizing DR-DOS for desktop markets towards embedded systems under Lineo and Linux-based platforms—leveraging legal successes against Microsoft to capitalize effectively on their technological assets.

Later releases

Following Lineo's acquisition in 2002, several former Lineo executives acquired the DR-DOS trademark and established DRDOS, Inc., operating as DeviceLogics L.L.C., to continue marketing DR-DOS for embedded applications. On March 30, 2004, DR-DOS 8.0 was launched, incorporating features such as FAT32 and extensive disk support, the ability to boot from ROM or Flash memory, multitasking capabilities, and a DPMI memory manager, all built upon kernel version 7.03.

In the fall of 2005, DRDOS, Inc. introduced DR-DOS 8.1, which enhanced FAT32 compatibility and was based on OpenDOS 7.01.xx. However, this version was retracted due to non-compliance with the GPL (refer to Controversies). Alongside sales, the company also provided an option for purchasing the DR-DOS rights for $25,000.

The source code of OpenDOS 7.01 served as the foundation for The DR-DOS/OpenDOS Enhancement Project, initiated in July 2002 with the goal of updating DR-DOS functionalities. This project brought improvements such as native support for large disks (LBA), integration of the FAT32 filesystem, better memory management, and compatibility with the FAT32+ extension that allows files up to 256 GB on FAT partitions. A work-in-progress release, DR-DOS 7.01.08 WIP, became available on July 21, 2011.

Starting in 2023, the most recent Enhanced DR-DOS edition (7.01.08 WIP) has been adapted to an open-source build environment that supports cross-compilation from non-DOS platforms. The kernel is compiled into a single binary file named KERNEL.SYS, which is compatible with boot loaders designed for FreeDOS kernels. This version has undergone various bug fixes and updates and continues to receive active maintenance as of October 2024.

Controversies

In October 2005, it was discovered that DR-DOS 8.1 included utilities sourced from FreeDOS and other projects without adhering to the GNU General Public License (GPL) requirements—specifically, failing to credit FreeDOS contributors or release source code. After FreeDOS developers raised concerns demanding GPL compliance, DRDOS, Inc. removed versions 8.1 and the unaffected 8.0 from its website.

Commands

Since DR-DOS version 3.31, internal commands like APPEND, ASSIGN, BATCH, DBG, DELQ, ERA, ERAQ, MORE, and SUBST have been supported. With the release of DR-DOS 5.0, BATCH was eliminated while HILOAD was introduced. Version 6.0 added internal commands including GOSUB, IDLE, RETURN, and SWITCH; at this stage ASSIGN and SUBST were shifted to external commands. The internal commands ECHOERR and PAUSEERR existed in DR-DOS 6.0 but were generally disabled by default. The MORE command remained internal through PalmDOS but transitioned to an external command in Novell DOS 7; DBG was removed by Novell DOS 7 or possibly earlier versions. Internal commands LOADHIGH (LH) and TRUENAME were incorporated starting with update 8 and DR DOS 6.0 (1993). APPEND was internal in DR-DOS 6.0 but became external with Novell DOS 7.

Internal commands

The following list represents internal commands supported by DR DOS 6.0:


Subcommands for batch processing

The batch processing subcommands available in DR DOS 6.0 consist of the following:



External commands

The following external commands are supported by DR  DOS 6.0:



See also

Further reading

  • Digital Research, Inc. (1990). DR DOS 5.0 Retail box with lid. Digital Research, Inc. Part Number 1176-6114-001
  • Digital Research, Inc. (May 1990). DR DOS 5.0 User Guide, 1st ed., 501 pages. Part Number 1176-2004-002
  • Digital Research, Inc. (May 1990). ViewMAX User Guide, 1st ed., 88 pages. Part Number 1174-2004-002
  • Digital Research, Inc. (August 1990). DR DOS 5.0 Release Notes, 11 pages. Part Number 1176-1001-002
  • Digital Research, Inc. (August 1991). DR DOS 6.0 Software performance report. Part No. 000-1200-00
  • Digital Research, Inc. (August 1991). DR DOS 6.0 User Guide, 2nd ed., 698 pages. Part Number 1182-2004-002
  • Digital Research, Inc. (August 1991). ViewMAX User Guide, 2nd ed., 106 pages. Part Number 1192-2054-002
  • Novell Desktop Systems Group / Digital Research (January 7, 1993). DRTIPS.ZIP (orig. 1992)

External links

  1. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Rosch_1991_DR5
  2. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Jones_2004
  3. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Caldera_1998_Subsidiaries
  4. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Lea_1999_UK
  5. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Caldera_1999_Lineo
  6. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named ct_2000
  7. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named OnTrack_1999_ER
  8. ↑ 8.0 8.1 Cite error: Invalid <ref> tag; no text was provided for refs named Paul_2003_IBMBIO85_108
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