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PalmDOS

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Digital Research, Inc.
Company typePrivate
IndustrySoftware
FoundedJanuary 1, 1970; 56 years ago (1970-01-01)
FounderGary A. Kildall
FateAcquired by Novell
SuccessorNovell DOS, Caldera DR-DOS, OpenDOS
Headquarters
Pacific Grove / Monterey
,
United States
Area served
Worldwide
Key people
Gary A. Kildall (founder)
ProductsDR-DOS, Concurrent DOS, DOS Plus, Multiuser DOS, PalmDOS

DR-DOS (styled as DR DOS without a hyphen up to version 6.0) is a disk operating system designed for IBM PC compatible computers. It was initially created by Digital Research, Inc., led by Gary A. Kildall, and evolved from Concurrent PC DOS 6.0, itself an advanced iteration of 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, 3.31, matched the version numbering of MS-DOS at the time. The first retail edition, DR DOS 5.0, appeared in 1990 and received widespread praise, positioning DR-DOS as Microsoft's primary rival in the MS-DOS market. Microsoft introduced MS-DOS 5.0 more than a year afterward. Among its innovations, DR-DOS offered ViewMAX, a graphical user interface extension. Version 6.0 was released in 1991.

Following Digital Research's acquisition by Novell, the operating system was renamed Novell DOS 7.0 in 1994. Later ownership changes brought the product under Caldera, which issued updated versions partially open-sourced under the Caldera brand and briefly rebranded it as OpenDOS. The last desktop edition, Caldera DR-DOS 7.03, was published in 1999 before the software shifted focus toward embedded applications under Caldera and subsequently DeviceLogics.

CP/M Foundations

Digital Research initially developed CP/M for 8-bit processors like the Intel 8080 and Z80, spawning several derivatives including CP/M-86 for the Intel 8086 and 8088 CPUs. Although CP/M held a dominant position in non-proprietary personal computers during the mid-1970s, the introduction of the IBM PC in 1981 caused a significant market realignment.

In 1980, IBM approached Digital Research to obtain an x86 version of CP/M; however, contractual disagreements halted these talks. IBM then collaborated with Microsoft, which had purchased 86-DOS from Seattle Computer Products. This software evolved into Microsoft’s MS-DOS and IBM PC DOS. Digital Research argued that PC DOS/MS-DOS bore too close a resemblance to CP/M and threatened legal action. By 1982, IBM agreed to offer Digital Research’s CP/M-86 alongside PC DOS but priced it at $240 compared to PC DOS's $40 cost. Due to this price difference and limited software availability, CP/M-86 saw minimal customer adoption.

Digital Research faced challenges promoting CP/M-86 along with its successors MP/M-86 and Concurrent CP/M-86. Unable to keep pace with Microsoft-IBM’s software ecosystem dominance, they adapted Concurrent CP/M-86 to support MS-DOS applications. This capability was publicly demonstrated in December 1983 and subsequently released as Concurrent DOS 3.1 in March 1984 for hardware manufacturers. While Concurrent DOS later developed into Multiuser DOS and REAL/32, it remained expensive and less practical for typical desktop users.

To bridge this gap, Digital Research introduced DOS Plus versions 1.0 through 2.1 between 1985 and 1988—a simplified single-user variant of Concurrent DOS that offered multitasking alongside limited DOS compatibility. Building on this foundation, Digital Research unveiled DR DOS in 1988 as a fully native DOS-compatible operating system.

Although headquartered in Pacific Grove and later Monterey, California, much of the engineering work on DOS Plus, Concurrent DOS variants, Multiuser DOS, DR DOS, and PalmDOS took place at Digital Research’s European Development Centre located in Hungerford, Berkshire, UK, with additional contributions from Digital Research GmbH based in Munich, Germany.

Initial DR DOS Release

To meet OEM requirements and overcome limitations found in MS-DOS, Digital Research introduced a new DOS operating system in 1987. A pivotal agreement with Kazuhiko "Kay" Nishi of ASCII Corporation facilitated DR DOS's entry into the Japanese OEM market. The inaugural version became available on May 28, 1988.

Versioning was synchronized with MS-DOS feature sets; the first public edition was DR DOS 3.31, aligning with Compaq's MS-DOS 3.31 that supported large disks (FAT16B/"BIGDOS"). Externally, DR DOS 3.31 presented itself as "IBM PC DOS 3.31," while internally its BDOS kernel carried version 6.0, reflecting its roots in Concurrent DOS 6.0 but without multitasking or CP/M API capabilities, incorporating an IBM-compatible DOS-BIOS (DRBIOS.SYS) and BDOS kernel (DRBDOS.SYS). The disk OEM label read "DIGITAL␠".

Enhanced command line utilities were part of DR DOS, offering help functions, detailed error messages, sophisticated command history and editing through the HISTORY directive, plus kernel-level protection for files and directories via passwords. Priced lower than MS-DOS and designed to be ROMable from inception—the ROM-based variant named ROS (ROM Operating System)—DR DOS attracted attention from PC manufacturers, leading to multiple system updates.

At a time when MS-DOS was solely available through OEM bundling, DR DOS quickly gained popularity by being offered directly to consumers through retail starting with version 3.4x.

Notable releases included DR DOS 3.31 (BDOS 6.0, June 1988, OEM-only), followed by versions 3.32 (August 1988), 3.33 (September 1988), 3.34 (OEM-only), 3.35 (October 1988), 3.40 (January 1989), and 3.41 (BDOS 6.3, June 1989, both OEM and retail). Many versions had variants tailored to different hardware platforms. While most OEMs preserved the DR DOS branding, the product was also marketed as EZ-DOS 3.41 (or EZ-DOS 4.1) by 2001 Sales, Inc.

DR DOS Version 5.0

Released in May 1990 under the codename "Leopard," DR DOS 5.0 maintained compatibility by identifying itself as "PC DOS 3.31," though internally it operated on a BDOS kernel version 6.4. To avoid association with MS-DOS version 4.0, this release skipped that number entirely and introduced ViewMAX, a graphical file management shell based on GEM technology, accompanied by the slogan "Digital Research - We make computers work."

Significant advancements included the patented BatteryMAX power management system, integrated disk-caching software named DRCACHE, a remote file transfer utility called FILELINK, a cursor customization tool known as CURSOR, and an improved memory management utility labeled MemoryMAX. System files were renamed to IBMBIO.COM and IBMDOS.COM, enabling versatile disk storage through an enhanced boot sector loader mechanism. The OEM label was updated to "IBM␠␠3.3".

DR DOS 5.0 pioneered load-high functionality by relocating its kernel and disk buffers into the High Memory Area (HMA)—the initial 64 KB of extended memory accessible in real mode—thus freeing up essential conventional memory within the first 640 KB of RAM for application use.

On systems equipped with the Intel 80386 processor, its EMS memory manager allowed loading DOS device drivers into upper memory blocks, further boosting available base memory space. Unlike MS-DOS—which relied on third-party utilities such as QEMM for this capability—DR DOS incorporated this feature natively, resulting in substantially more free conventional memory on both Intel 286 and 386 platforms.

While typical MS-DOS configurations left only about 300–400 KB of free conventional memory after loading drivers for peripherals like mice, multimedia devices, and networking hardware, DR DOS 5.0 could preserve up to approximately 620 KB free with manual optimization—almost the entire conventional memory limit of 640 KB. The MEMMAX +V option could extend this further by utilizing unused graphics adapter memory for an additional 64–96 KB.

This large amount of free conventional memory caused compatibility challenges with certain legacy software employing address wrapping techniques that assumed less low memory availability. To mitigate this issue, DR DOS provided the MEMMAX -L command to pre-allocate a low-memory block forcing such applications to load above it—though this reduced overall usable conventional memory capacity. By default, MEMMAX was set to +L to maximize available application memory space.

DR DOS 6.0 / Microsoft’s Competitive Response

Facing intense rivalry, Microsoft unveiled MS-DOS 5.0 in May 1990 and officially launched it in June 1991, incorporating advanced capabilities akin to those found in DR DOS, notably improved memory management.

Digital Research swiftly countered by releasing DR DOS 6.0 in September 1991, internally designated BDOS version 6.7 and codenamed "Buxton." To ensure compatibility, it presented itself as "IBM PC DOS 3.31" to software applications. Significant business-oriented enhancements included integrated SuperStor disk compression to optimize hard disk utilization and an undelete feature for file recovery, developed by Roger A. Gross.

A major innovation in DR DOS 6.0 was TASKMAX, a task-switching utility implementing the industry-standard multitasking API that enabled multiple applications to run concurrently by suspending background processes until reactivated. TASKMAX utilized XMS memory on systems with 286 processors or higher and provided basic Copy & Paste functionality between programs. This API also allowed graphical shells such as ViewMAX or PC/GEOS to replace the traditional text-based task switcher menu, thereby enhancing user interaction within a graphical user interface environment.

Microsoft responded with MS-DOS 6.0, which incorporated features that closely paralleled those introduced in DR DOS 6.0.

In December 1991, a pre-release version of Windows 3.1 contained the contentious AARD code designed to detect non-Microsoft DOS variants and display a non-critical error message. Digital Research promptly issued a patch for DR DOS 6.0 that circumvented this validation check by rearranging internal memory structures without affecting functionality. This patched "business update" edition was made available within six weeks of Windows 3.1’s debut, ensuring seamless Windows operation on both DR DOS and its successor Novell DOS. Although the detection mechanism remained embedded, it was disabled in the final Windows 3.1 release.

By July 1992, Digital Research Japan introduced DR DOS 6.0/V, a localized Japanese edition compatible with DOS/V, alongside a Korean version, thereby broadening market penetration in Asia.

PalmDOS

In 1992, under Novell’s ownership since July 1991, Digital Research launched "Merlin," subsequently marketed as NetWare PalmDOS 1—a streamlined derivative of DR DOS 6.0 tailored for the nascent palmtop and PDA segments.

PalmDOS was the first in its lineage to employ the BDOS 7.0 kernel featuring native DOS-compatible internal data structures, enhancing software compatibility while minimizing kernel footprint—an essential factor for portable devices. Unlike earlier DR DOS releases, PalmDOS implemented a true Current Directory Structure (CDS), restricting directory path lengths to a maximum of 66 characters, aligning with MS-DOS/PC DOS conventions. To preserve kernel compactness and maintain compatibility with Windows applications, PalmDOS identified itself as "PC DOS 3.31" when queried by programs.

Engineered for execution from ROM, PalmDOS supported PCMCIA hardware (with DPMS power management), energy-saving features through BatteryMAX and the patented dynamic idle detection driver $IDLE$, as well as MINIMAX task switching designed for Personal Information Manager (PIM) applications running directly from ROM via Execute-In-Place (XIP). The PCMCIA stack development involved Ian H. S. Cullimore, a prominent contributor to the PCMCIA initiative.

Novell DOS 7 / Novell's Role

Novell DOS was the name Novell Corporation assigned to DR DOS following their acquisition of Digital Research in 1991. This operating system often surpassed MS-DOS versions in both functionality and speed. By 1993, Novell DOS 7 had outperformed competitors such as PC DOS 6.1 and MS-DOS 6.2/6.3.

Under CEO Robert J. Frankenberg, Novell undertook significant streamlining of its product portfolio, divesting assets like Btrieve and discontinuing Novell DOS alongside other software titles. The company licensed technology from Stac Electronics for use in both Novell DOS and its NetWare network operating system. On July 23, 1996, Novell transferred ownership of the DR DOS line to Caldera, which intended to bundle the DOS OS with its OpenLinux distribution.

Marc Perkel has asserted that he influenced Novell’s purchase of Digital Research with the vision of creating "NovOS." Novell sought to break Microsoft’s dominance by acquiring Digital Research, as well as WordPerfect and Borland products, and investing in Unix technologies. The anticipated DR DOS 7.0 release (codenamed "Panther") was delayed while Novell developed a Unix-like multi-user security extension compatible with Multiuser DOS and two graphical user interfaces: ViewMAX 3 (based on GEM) and "Star Trek," a port of Apple's System 7.1 running atop the multitasking system "Vladivar."

When Novell DOS 7 (NWDOS) launched in December 1993, these ambitious features were absent, leading to some disappointment despite widespread acclaim for its overall quality.

In Germany, a vigorous marketing campaign employing the slogan "Trau keinem DOS unter 7" ("Don't trust any DOS below 7") contributed to sales reaching approximately 1.5 million units by early 1994 and attracted over 3,000 retail partners. Distribution channels included OEM agreements, mail order, and authorized resellers.

A significant enhancement was the inclusion of Personal NetWare (PNW), Novell’s upgraded peer-to-peer networking solution that succeeded NetWare Lite but was incompatible with Microsoft's expanding Windows networking protocols. PNW required complex configuration to operate alongside Microsoft systems and achieved only limited market penetration.

Novell DOS 7 integrated the DOSMGR API with an updated BDOS kernel reporting as DOS version 6.0 and OEM ID "IBM," ensuring smooth compatibility with Windows environments.

The operating system introduced sophisticated memory management capabilities supporting DPMI and DPMS standards, flexible loadhigh commands, and genuine preemptive multitasking for multiple DOS applications running within virtual DOS machines (VDMs) through MultiMAX technology. TASKMGR handled task management similarly to earlier iterations but utilized EMM386’s /MULTI option to provide a native 32-bit protected mode core supporting multitasking, multithreading, hardware virtualization, and domain control over VDMs—fully compatible with Windows multitasking.

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

Although several bug-fix updates addressed stability concerns, active development ceased by September 1994 as Microsoft prepared to launch Windows 95; maintenance concluded in January 1996 after more than fifteen updates.

Post-Novell Period

Seeking a DOS operating system to package with their OpenLinux distribution, Caldera acquired the DR DOS product line from Novell on July 23, 1996, since it no longer held strategic value for Novell.

Confronted with competition from IBM's PC DOS 6.3 and Caldera's own DR-DOS, Microsoft limited Windows 95 compatibility exclusively to their DOS variant, prompting a notable lawsuit supported by the Canopy Group. Despite Microsoft's efforts to dismiss the case, it was settled out of court on January 7, 2000, for $280 million.

In August 1996, Roger A. Gross—an original DR-DOS developer—proposed revitalizing DR-DOS development with added Windows 95 compatibility. Following a September meeting in Utah involving Caldera executives including Raymond John Noorda, Gross was hired to form a UK branch. Caldera UK Ltd., incorporated on September 20, 1996, began advancing DR-DOS development in Andover, Hampshire by recruiting former Novell EDC engineers along with new talent.

Over the subsequent two years, significant enhancements were introduced: a TCP/IP stack derived from LAN WorkPlace for DOS, a 32-bit protected mode web browser named DR-WebSpyder, POSIX Pthreads multitasking extensions, long filename (LONGNAME) support, and FAT32 support (DRFAT32). Andrew Schulman joined as a consultant to assist with "WinGlue," a confidential project aimed at producing Windows 95/98-compatible DR-DOS versions that replaced MS-DOS components. Demonstrated at CeBIT in 1998, this initiative evolved into "WinBolt," which remained unreleased but played a vital role in the Caldera v. Microsoft litigation.

Caldera UK officially launched OpenDOS 7.01 on February 3, 1997—essentially an updated version of Novell DOS 7 without patches from later Novell updates due to lost source code at Novell. This release excluded bundled utilities such as the Search&Destroy virus scanner but included newer versions of PNUNPACK and NetWars.

In May 1997, portions of OpenDOS 7.01 were briefly made available under restrictive open source licenses but were subsequently reverted to proprietary status to safeguard commercial interests.

Following beta releases in late 1997, Caldera released DR-OpenDOS 7.02 in December (later renamed Caldera DR-DOS 7.02). This edition reported BDOS version 7.3 internally and featured enhanced BIOS and BDOS functions with improved compatibility for Windows 9x and third-party disk compression tools like DriveSpace. It introduced a diagnostics mode, integrated debugger support, expanded CONFIG.SYS capabilities enabling flexible boot menus and multiple configurations, along with improved memory management options that freed additional conventional memory—crucial for running advanced drivers and shells such as 4DOS.

The NLS subsystem was upgraded to support multiple COUNTRY.SYS files with dynamic parsing compatible with MS-DOS/PC DOS formats; it also introduced ISO 8601 date formatting and Euro currency support. DR-DOS 7.02 achieved full Year-2000 compliance with an updated FDISK utility supporting FAT32 partitions (excluding LBA). Missing patches from Novell were retrofitted to complete system improvements.

Some legacy applications encountered compatibility issues due to the updated BDOS version number; these were resolved via an enhanced SETVER utility capable of hierarchically faking both DOS and BDOS versions to maintain compatibility with older software expecting earlier versions of Novell DOS or DR-DOS.

A conflict arose between the new HIFILES feature and QEMM's DOS-UP memory manager due to differing handle structures; this was addressed through a patch that selectively altered behavior at the expense of compatibility trade-offs between different Windows versions.

In August 1998,[1] Caldera established two subsidiaries: Caldera Systems, Inc., focusing on Linux-related business endeavors, and Caldera Thin Clients, Inc., dedicated to embedded systems and thin-client markets.[2]

DR-DOS version 7.03 was pre-released during Christmas of 1998 and officially launched on January 6, 1999 by Caldera UK. This release featured improved memory managers with enhanced DPMI multitasker support plus additional utilities like DEVLOAD and DRMOUSE but introduced a modified FAT OEM label that caused interoperability challenges with other operating systems (workarounds involved NOVOLTRK). This marked the final desktop-centric DR-DOS release.

After Roger Gross resigned in early 1999, Caldera shifted DR-DOS development operations back to the United States; consequently the successful UK division was closed.[3][4] Development responsibilities moved under Caldera Thin Clients (renamed Lineo, Inc. on July 20, 1999), which pivoted towards embedded Linux solutions based on a streamlined OpenLinux variant called Embedix. Lineo reissued DR-DOS 7.03 mid-1999 without modifications.[5]

Subsequent independent OEM editions included DR-DOS versions 7.04 (August 19, 1999) and 7.05 (November 30, 1999), featuring minimal kernels with native FAT32 plus large disk support bundled within products such as Ontrack's Easy Recovery 5 that replaced older redirector drivers.[6] These releases internally reported BDOS version 7.3 but externally identified as "PC DOS 7.10" to signal FAT32 integration.

DR-DOS kernels from these versions could be combined—for example pairing IBMBIO.COM from newer releases with IBMDOS.COM from earlier ones—to enable LBA support beyond desktop-focused editions.

Version 7.06 (December 14, 1999) consolidated kernel components into a single executable bootable by MS-DOS 7.10 boot sectors but incompatible with native DR-DOS boot sectors.[7] The subsequent release 7.07 introduced unified bootstrap loaders supporting CHS/LBA disk access across FAT12/16/32 file systems along with multiple boot standards—including those used by PC DOS/MS-DOS/Windows—facilitating seamless multi-boot configurations among diverse operating systems.[8]

Subsequent Releases

Following the acquisition of Lineo in 2002, former Lineo executives acquired the rights to the DR-DOS brand 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 support for FAT32 and large storage devices, ROM/Flash boot functionality, 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. This release was later retracted due to infringements of the GPL license (refer to Controversies). Additionally, the company provided an option to purchase the DR-DOS source code for $25,000.

The OpenDOS 7.01 codebase formed the basis for The DR-DOS/OpenDOS Enhancement Project, initiated in July 2002 with the goal of updating DR-DOS’s features. Improvements encompassed native support for large disks via LBA and FAT32, enhanced memory management, along with compatibility for the FAT32+ extension allowing file sizes up to 256 GB on FAT partitions. A work-in-progress version, DR-DOS 7.01.08 WIP, was released on July 21, 2011.

Starting in 2023, the latest Enhanced DR-DOS build (7.01.08 WIP) was adapted to an open-source compilation environment that facilitates cross-platform kernel and shell builds beyond traditional DOS environments.[9] The kernel compiles into a unified binary named KERNEL.SYS compatible with FreeDOS boot loaders. This version has been continuously updated with bug fixes and remains actively maintained as of October 2024.

Controversies

In October 2005, it was discovered that DR-DOS 8.1 contained utilities sourced from FreeDOS and other projects without proper attribution or source disclosure, thus breaching the terms of the GNU General Public License (GPL). After FreeDOS developers raised concerns demanding GPL adherence, DRDOS, Inc. removed both versions 8.1 and 8.0 from their distribution site.

Commands

Since DR-DOS version 3.31, internal commands have included APPEND, ASSIGN, BATCH, DBG, DELQ, ERA, ERAQ, MORE, and SUBST. With the release of DR-DOS 5.0, BATCH was eliminated while HILOAD was introduced.[10][11] Version 6.0 added internal commands such as GOSUB, IDLE, RETURN, and SWITCH.[11] From this version onward ASSIGN and SUBST were transitioned to external commands.[11] Internal commands ECHOERR and PAUSEERR were present in DR-DOS 6.0 (and Multiuser DOS) but typically disabled by default.[10] The MORE command remained internal through PalmDOS but became external starting with Novell DOS 7; DBG was removed by Novell DOS 7; internal commands LOADHIGH, LH, and TRUENAME were added beginning with update 8 and DR DOS 6.0 (1993). APPEND shifted from an internal command in DR-DOS 6.0 to external in Novell DOS 7.[12]

Internal Commands

The following internal commands are supported within DR DOS 6.0:


Batch processing subcommands

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



External commands

The external commands supported by DR  DOS 6.0 include: 


* TOUCH
* TREE
* UNDELETE
* UNFORMAT
* UNINSTAL
* XCOPY
* XDEL
* XDIR


See also

Further reading

  • Digital Research, Inc. (1990) DR DOS 5.0 Retail box with lid
  • Digital Research, Inc. (May 1990) DR DOS 5.0 User Guide, 501 pages
  • Digital Research, Inc. (May 1990) ViewMAX User Guide, 88 pages
  • Digital Research, Inc. (August 1990) DR DOS 5.0 Release Notes, 11 pages
  • Digital Research, Inc. (August 1991) DR DOS 6.0 Software performance report
  • Digital Research, Inc. (August 1991) DR DOS 6.0 User Guide, 698 pages
  • Digital Research, Inc. (August 1991) ViewMAX User Guide, 106 pages
  • Novell Desktop Systems Group (January 7, 1993) DRTIPS.ZIP (Digital Research / Novell)

External links

  1. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Jones_2004
  2. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Caldera_1998_Subsidiaries
  3. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Richardson_1999_Ball
  4. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Collins_2000
  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 Paul_2003_IBMBIO85_108
  8. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Paul_2002_OEM
  9. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named edrdos_2023
  10. ↑ 10.0 10.1 Cite error: Invalid <ref> tag; no text was provided for refs named Paul_1997_DRDOS6UN
  11. ↑ 11.0 11.1 11.2 Cite error: Invalid <ref> tag; no text was provided for refs named 4DOS_8.00_HELP
  12. ↑ citation needed
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