DOS (DR DOS, without hyphen up to and including version 6.0) is an
operating system of the
DOS family, written for
IBM PC -compatible
personal computers . It was originally developed by
Gary Kildall 's
Digital Research and derived from Concurrent PC
DOS 6.0, which was an
advanced successor of
CP/M-86 . As ownership changed, various later
versions were produced with names including
DOS and Caldera
* 1 History
* 1.1 Origins in
* 1.2 First DR
* 1.3 Version 5.0
* 1.4 Competition from
* 1.5 Patching to counter
* 1.6 Palm
* 1.7 Contribution by
* 1.8 After
* 1.9 Recent versions
* 2 Controversies
* 3 See also
* 4 References
* 5 Further reading
* 6 External links
ORIGINS IN CP/M
Digital Research 's original
CP/M for the 8-bit
Intel 8080 and Z-80
based systems spawned numerous spin-off versions, most notably CP/M-86
Intel 8086 /8088 family of processors. Although
dominated the market, and was shipped with the vast majority of
non-proprietary-architecture personal computers, the
IBM PC in 1981
brought the beginning of what was eventually to be a massive change.
IBM originally approached Digital Research, seeking an x86 version of
CP/M. However, there were disagreements over the contract, and IBM
withdrew. Instead, a deal was struck with
Microsoft , who purchased
another operating system, 86-
DOS , from
Seattle Computer Products .
DOS . 86-DOS' command
structure and application programming interface imitated that of CP/M.
Digital Research threatened legal action, claiming PC DOS/MS-
DOS to be
too similar to CP/M.
IBM settled by agreeing to sell their x86 version
CP/M-86 , alongside PC DOS. However, PC
DOS sold for $40,
CP/M-86 had a $240 price tag. The proportion of PC buyers
prepared to spend six times as much to buy
CP/M-86 was very small, and
the availability of compatible application software, at first
decisively in Digital Research's favor, was only temporary.
Digital Research fought a long losing battle to promote
its multi-tasking multi-user successors
MP/M-86 and Concurrent CP/M-86
, and eventually decided that they could not beat the Microsoft-IBM
lead in application software availability, so they modified Concurrent
CP/M-86 to allow it to run the same applications as MS-
DOS and PC DOS.
This was shown publicly in December 1983 and shipped in March 1984
DOS 3.1 (a.k.a. C
DOS with B
DOS 3.1) to hardware vendors.
DOS continued to evolve in various flavours over the
years to eventually become Multiuser
DOS , it was not specifically
tailored for the desktop market and too expensive for single-user
applications. Therefore, over time two attempts were made to sideline
Digital Research developed
DOS Plus 1.1 to 2.1 , a
stripped-down and modified single-user derivative of Concurrent DOS
4.1 and 5.0 , which ran applications for both platforms, and allowed
switching between several tasks as did the original CP/M-86. Its DOS
compatibility was limited, and
Digital Research made another attempt,
this time a native
DOS system. This new disk operating system was
launched in 1988 as DR DOS.
Although DRI was based in Pacific Grove and later in Monterey ,
California, USA, the work on
DOS Plus started in Newbury , Berkshire,
Digital Research Europe had its OEM Support Group
(51°24′22″N 1°19′35″W / 51.40612°N 1.326374°W /
51.40612; -1.326374 (
Digital Research (UK) Ltd., Oxford House,
12-20 Oxford Street, Newbury, Berkshire, UK) ) located since 1983.
Since 1986, most of the operating system work on Concurrent
and XM , Multiuser
DOS , DR
DOS and Palm
DOS was done in Digital
Research's European Development Centre (EDC) (51°24′52″N
1°30′47″W / 51.414478°N 1.512946°W / 51.414478;
Digital Research (UK) Ltd., Station Road, Hungerford,
Berkshire, UK) and 51°25′13″N 1°30′55″W /
51.420339°N 1.515223°W / 51.420339; -1.515223 (Digital
Research (UK) Ltd., Charnham Park, Hungerford, Berkshire, UK) ) in
Hungerford , Berkshire, UK.
As requested by several OEMs
Digital Research started to plan develop
DOS operating system addressing the shortcomings left by MS-DOS
in 1987. The first DR
DOS version was released on 28 May 1988.
Version numbers were chosen to reflect features relative to MS-DOS;
the first version promoted to the public was DR
DOS 3.31, which
offered features comparable to Compaq MS-
DOS 3.31 with large disk
FAT16B a.k.a. "BIGDOS"). DR
DOS 3.31 reported itself as "IBM
DOS 3.31", while the internal B
Basic Disk Operating System
Basic Disk Operating System )
kernel version was reported as 6.0, single-user nature, reflecting its
origin as derivative of Concurrent
DOS 6.0 with the multitasking and
multiuser capabilities as well as
CP/M API support stripped out and
XIOS replaced by an IBM-compatible
DOS-BIOS . The system files
DRBIOS.SYS (for the DOS-BIOS) and
DRBDOS.SYS (for the BDOS
kernel), the disk OEM label used was "DIGITAL␠".
DOS offered some extended command line tools with command line
help, verbose error messages, sophisticated command line history and
editing (HISTORY directive) as well as support for file and directory
passwords built right into the kernel. It was also cheaper to license
than MS-DOS, and was ROMable right from the start. The ROMed version
DOS was also named ROS (ROM Operating System). DRI was
approached by a number of PC manufacturers who were interested in a
third-party DOS, which prompted several updates to the system.
At this time, MS-
DOS was only available to OEMs bundled with
hardware. Consequently, DR
DOS achieved some immediate success when it
became possible for consumers to buy it through normal retail channels
Known versions are DR
DOS 3.31 (B
DOS 6.0, 1988-06, OEM only), 3.32
DOS 6.0, 1988-08-17, OEM only), 3.33 (B
DOS 6.0, 1988-09-01, OEM
only), 3.34 (B
DOS 6.0, OEM only), 3.35 (B
DOS 6.0, 1988-10-21, OEM
only), 3.40 (B
DOS 6.0, 1989-01-25), 3.41 (B
DOS 6.3, 1989-06, OEM and
retail). Like MS-DOS, most of them were produced in several flavors
for different hardware. While most OEMs kept the DR
designation, one OEM version is known to be called EZ-
Further information: Comparison of
DOS operating systems
DOS version 5.0 (code-named "Leopard") was released in May 1990,
still reporting itself as "PC
DOS 3.31" for compatibility purposes,
but internally indicating a single-user B
DOS 6.4 kernel. (Version 4
was skipped to avoid being associated with the relatively unpopular
DOS 4.0 .) This introduced
ViewMAX , a GEM -based
management shell, the patented
BatteryMAX power management system,
bundled disk-caching software, and also offers vastly improved memory
management. For compatibility purposes, the DR
DOS 5.0 system files
were now named
IBMBIO.COM (for the DOS-BIOS) and
IBMDOS.COM (for the
DOS kernel), and the OEM label in boot sectors was changed to
"IBM␠␠3.3". Front and rear views of the
diskless workstation, bundled with DR
DOS 5.0, based on an Intel 80286
processor and produced by Taiwan's
Flytech Technology circa 1991.
First, the DR
DOS kernel and structures such as disk buffers can be
located in the
High Memory Area (HMA), the first 64 KB of extended
memory which are accessible in real mode due to an incomplete
compatibility of the 80286 with earlier processors. This freed up the
equivalent amount of critical "base" or conventional memory , the
first 640 KB of the PC's RAM – the area in which all MS-DOS
Intel 80386 machines, DR DOS's EMS memory manager
allowed the OS to load
DOS device drivers into upper memory blocks,
further freeing base memory. For more information on this, see the
article on the
Upper Memory Area (UMA).
DOS 5.0 was the first
DOS to integrate such functionality into the
base OS (loading device drivers into upper memory blocks was possible
using third-party software like
QEMM ). This allowed it, on a 386
system, to provide significantly more free conventional memory than
any other DOS. Once drivers for a mouse, multimedia hardware and a
network stack were loaded, an MS-
DOS machine typically might only have
300 to 400 KB of free conventional memory – too little to run much
late-1980s software. DR
DOS 5.0, with a little manual tweaking, could
load all this and still keep all of its conventional memory free –
allowing for some necessary
DOS data structures, as much as 620 KB out
of the 640 KB.
DOS left so much conventional memory available, some old
programs utilizing certain address wrapping techniques failed to run
properly as they were now loaded unexpectedly (or, under MS-DOS,
"impossibly") low in memory – inside the first 64 KB segment (known
as "low memory"). Therefore, DR
DOS 5.0's new MEMMAX -L command worked
around this by pre-allocating a chunk of memory at the start of the
memory map in order for programs to load above this barrier (but with
less usable conventional memory then). By default, MEMMAX was
configured for +L, so that applications could take advantage of the
COMPETITION FROM MICROSOFT
Faced with substantial competition in the
DOS arena, Microsoft
responded with an announcement of a yet-to-be released MS-
DOS 5.0 in
May 1990. This would be released in June 1991 and include similar
advanced features to those of DR DOS. It included matches of the DR's
enhancements in memory management.
Almost immediately in September 1991,
Digital Research responded with
DOS 6.0, code-named "Buxton". DR
DOS 6.0, while already at BDOS
level 6.7 internally, would still report itself as "
DOS applications for compatibility purposes. This bundled in
SuperStor on-the-fly disk compression, to maximize available hard disk
space, and file deletion tracking and undelete functionality by Roger
DOS 6.0 also includes a task-switcher named TASKMAX, support for
the industry-standard task-switching API to run multiple applications
at the same time. In contrast to Digital Research's Multiuser DOS
(successor of Concurrent
DOS in the multi-user products line), which
DOS applications in pre-emptively multitasked virtual DOS
machines, the DR
DOS 6.0 task switcher would freeze background
applications until brought back into the foreground. While it runs on
x86-machines, it is able to swap to XMS memory on 286+ machines.
TASKMAX did support some Copy "> It was larger and introduced many new
bugs, and the main functional addition was Novell's second attempt at
a peer-to-peer networking system, Personal
NetWare (PNW). This worked
and was better than its predecessor,
NetWare Lite (NWL), but it was
incompatible with Microsoft's networking system, now growing popular
with support in Windows for Workgroups,
Windows NT . A
considerable amount of manual configuration was needed to get both to
co-exist on the same PC, and Personal
NetWare never achieved much
DOS 7 implemented the DOSMGR API and internal data
structures had been updated, its B
DOS 7.2 kernel could report with a
DOS version of 6.0 and OEM ID "IBM" without risking compatibility
problems with Windows. Most tools would report this as "PC
DOS 6.1 also reported as
DOS 6.0 to applications.
DOS 7 introduced much advanced memory management including new
support for DPMI (
DOS Protected Mode Interface ) and DPMS (DOS
Protected Mode Services ) as well as more flexible loadhigh options.
It also introduced support for "true" pre-emptive multitasking of
DOS applications in virtual
DOS machines (VDM), similar to
Multiuser DOS, but now on the basis of a natively
environment, similar to Windows 386 Enhanced Mode without GUI. By
default, the bundled TASKMGR would behave similar to the former DR DOS
6.0 TASKMAX. However, if EMM386 was loaded with the option /MULTI,
EMM386 would load a natively 32-bit 386 Protected Mode operating
system core providing API support for pre-emptive multitasking,
multi-threading, hardware virtualization and domain management of
DOS machines. This API could be used by DR DOS-aware
applications. If TASKMGR was run later on, it would use these APIs to
instance the current 16-bit
DOS system environment, create virtual DOS
machines and run applications in them instead of using its own Real
Mode task-switcher support. The multitasker was compatible with
Windows, so that tasks started before launching Windows could be seen
as tasks under Windows as well.
DOS 7 and Personal
NetWare 1.0 also shipped with
NetWars , a
network-enabled 3D arcade game.
DOS 7 and Personal
NetWare required several bug-fix releases
and were not completely stable when the next development occurred.
With beta versions of Microsoft's "Chicago" (what would later become
Windows 95) in sight,
Novell wound down further development on Novell
DOS 7 in September 1994 and stopped maintenance in January 1996 after
more than 15 updates.
When Caldera approached
Novell looking for a
DOS operating system to
bundle with their
Novell sold the product line
off to Caldera on 23 July 1996, by which time it was of little
commercial value to them.
Between the Caldera-owned DR-
DOS and competition from IBM's PC DOS
Microsoft moved to make it impossible to use or buy the
subsequent Windows version,
Windows 95 , with any
DOS product other
than their own. Claimed by them to be a purely technical change, this
was later to be the subject of a major lawsuit brought in Salt Lake
City by Caldera with the help of the
Canopy Group . Microsoft
lawyers tried repeatedly to have the case dismissed but without
success. Immediately after the completion of the pre-trial deposition
stage (where the parties list the evidence they intend to present),
there was an out-of-court settlement on 7 January 2000 for an
undisclosed sum. This was revealed in November 2009 to be 280 million
In August 1996, the US-based
Caldera, Inc. was approached by Roger
Gross, one of the original DR-
DOS engineers, with a proposal to
DOS development and to make
Windows 95 run on DR-
would help the court case. Following a meeting in September 1996 in
Lindon , Utah, between Gross, Ransom Love , Bryan Sparks and Ray
Noorda , Gross was hired and tasked to set up a new subsidiary in the
UK. On 10 September 1996, Caldera announced the coming release of
DOS (COD) and their intent to also release the source code to the
system, and Caldera UK Ltd. (51°12′19″N 1°28′44″W /
51.20531°N 1.478786°W / 51.20531; -1.478786 (Caldera UK
Ltd., Aldwych House, Winchester Street, Andover, Hampshire, SP10 2EA,
UK) ) was incorporated on 20 September 1996. Gross hired some of the
original developers of the operating system from the
Novell EDC as
well as some new talents to continue work on the operating system in a
converted barn (51°11′18″N 1°29′15″W / 51.188306°N
1.487498°W / 51.188306; -1.487498 (Caldera UK Ltd., Norman
Court Barns, Norman Court Lane, Upper Clatford, Andover, Hampshire,
UK) ) at the periphery of Andover , Hampshire, UK, nearby the former
Digital Research and
Novell EDC. Besides other improvements and
enhancements all over the system, a string of new key features were
added subsequently over the course of the next two years, including a
TCP/IP stack (derived from
NetWare Mobile / LAN Workplace for DOS), a
DOS Protected Mode HTML 3.2 web-browser DR-WebSpyder
(originally based on source code from the Arachne web browser by
Michal Polák) with LAN and modem dialup, a
to the multi-tasker by Andy Wightman, long filename (LONGNAME) support
by Edward Hill as well as LBA and
FAT32 support (DRFAT32) by Matthias
Paul. Gross also hired Andrew Schulman (who had been, with Geoff
Chappell, instrumental in identifying the
AARD code in 1992) to work
as a consultant and, in Andover, join Paul in his work on "WinGlue", a
secret project to create a version of DR-
DOS compatible with Windows
95, 98 and 98 SE and replace its MS-
DOS 7.xx component. This was
CeBIT in March 1998, and later, in a small team,
developed into "WinBolt", both versions of DR-DOS, which remained
unreleased as of 2014 , but played an important role in the court case
Caldera UK officially released Caldera Open
DOS 7.01 in February 1997,
but this version was just
DOS 7 update 10 (as of December 1994)
with a new name, missing a year's worth of patches which had been
developed for the
DOS updates 11 (January 1995) to 15.2
(January 1996). This was due to parts of the
having been lost at
Novell meanwhile. Consequently, this version
still reported an internal B
DOS version of 7.2, identical to Novell
DOS 7. The new suite also lacked the SETFIFO command, which had been
added with one of the
DOS updates, as well as Fifth Generation
's Search the asking price is $ 25,000.
DOS 7.01 source code was a base for The DR-DOS/OpenDOS
Enhancement Project, set up in July 2002 in an attempt to bring the
functionality of DR-
DOS up to parity with modern PC non-Windows
operating systems. The project's added native support for large disks
(LBA ) and the
FAT32 file system, and several other enhancements,
including improved memory management and support for the new FAT32+
file system extension which allows files of up to 256 GB in size on
normal FAT partitions. DR-
DOS 7.01.08 was released on July 21, 2011.
In October 2005, it was discovered that DR-
DOS 8.1 included several
utilities from Free
DOS as well as other sources, and that the kernel
was an outdated version of the Enhanced DR-
DOS kernel. DR DOS, Inc.
failed to comply with the
GNU General Public License
GNU General Public License (GPL) by not
crediting the Free
DOS utilities to their authors and including the
source code. After complaints from Free
DOS developers (including the
suggestion to provide the source code, and hence comply with the GPL),
DR DOS, Inc. instead withdrew version 8.1, and also the unaffected
8.0, from its website.
MarioNet split web browser
* Comparison of
DOS operating systems
* Timeline of
DOS operating systems
* ^ http://drdos.com/company/about-drdos/
* ^ The rest of the story: How Bill Gates beat
Gary Kildall in OS
war, Part 1 ScobleShow: Videoblog about geeks, technology, and
Digital Research (1984): PC-Mode bridges
CP/M and PC-DOS.
Digital Dialogue - Employee Newsletter of
Digital Research Inc.,
Volume 3, Number 1, p. 3 ().
* ^ Digital Research: Concurrent™
DOS bridges PC-DOS, CP/M.
Digital Research News - For
Digital Research Users Everywhere, Volume
4, No. 2, p. 3, May 1984 (): '"Concurrent
DOS Release 3.1 is rapidly
gaining momentum and support from a wide range of microcomputer
manufacturers," Wandryk said. "Some 60 hardware companies have
licensed the product since it was released in early March."'
DOS Plus: A short history
* ^ A B C D E F G H I J K L Software Developer Caldera sues
Microsoft for Antitrust practices alleges monopolistic acts shut its
DOS operating system out of market Caldera News, 1996-07-24 ().
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* ^ The AARD Code
* ^ Dr. Dobb\'s Journal investigation
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DBCS -enabled version of
ViewMAX/2 running on DR
DOS 6.0/V and a hex dump of the corresponding
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DOS is 30 years old
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P.; Southwick, James T.; Folse III, Parker C.; Borchers, Timothy K.;
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* ^ BBC News BUSINESS Caldera vs
Microsoft - the settlement
* ^ "Exhibits to Microsoft\'s Cross Motion for Summary Judgment in
WordPerfect Case". Groklaw. 2009-11-23. Retrieved 2011-10-22.
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an obscure Utah company to prove what we already know: that Microsoft
is a monopoly. Seattle Weekly, 16 September 1998, (): "Furthermore,
Caldera claims that Microsoft's flagship product, Windows 95, is
nothing more than an "artificial tie" between its MS-
system and Windows graphic interface with no business justification
other than to keep competing underlying operating systems—like
Caldera's DR-DOS—off the market. To prove its point, Caldera will
soon release a piece of demonstration software called "Winbolt,"
which, it says, will allow users to install the
Windows 95 interface
atop DR-DOS. The demo will show, Caldera says, that there is no
significant technological advancement, or justified business
efficiency, to the combination of MS-
DOS with Windows in Windows 95."
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DOS 7 and Open
including the description of many undocumented features and internals.
It is part of the author's yet larger MPDOSTIP.ZIP collection
maintained up to 2001 and distributed on many sites at the time. The
provided link points to a HTML-converted older version of the
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DOS 8.00 online
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Windows NT .CPI, and
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alt.msdos.programmer. Retrieved 2006-10-14.
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* ^ A B C Caldera. Embedded
Linux moved to top priority at Lineo,
Inc., formerly known as Caldera Thin Clients, Inc.. Caldera, Inc.
press-release as of 1999-07-20 ().
* ^ http://www.freedos.org/freedos/news/press/2000-drdos-hist.txt
* ^ http://drdos.moriy.com/files/autoexec.gif
* ^ http://drdos.moriy.com/files/configsys.gif
* ^ FREE SOFTWARE FOR
DOS — Operating Systems
* ^ A B http://www.freedos.org/freedos/news/press/2005-drdos.txt
* ^ DR
DOS Buy Out DR
DOS Embedded DOS
* ^ Welcome to the DR-DOS/Open
DOS Enhancement Project!
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* Official website
* Enhanced DR-DOS/Open
DOS 7 online manual