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
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 OpenDOS.
1.1 Origins in CP/M
1.2 First DR
1.3 Version 5.0
1.4 Competition from Microsoft
1.5 Patching to counter Microsoft
1.7 Contribution by Novell
1.8 After Novell
1.9 Recent versions
3 See also
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 for the Intel 8086/8088 family of processors. Although CP/M
had 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
IBM originally approached Digital Research, seeking an x86
version of CP/M. However, there were disagreements over the contract,
IBM withdrew. Instead, a deal was struck with Microsoft, who
purchased another operating system, 86-DOS, from
Seattle Computer Products. This became
IBM PC 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
IBM settled by agreeing to sell their x86 version of CP/M,
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 CP/M-86
and its multi-tasking multi-user successors
MP/M-86 and Concurrent
CP/M-86, and eventually decided that they could not beat the
IBM lead in application software availability, so they
CP/M-86 to allow it to run the same applications
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. While Concurrent
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 the product.
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, UK, where 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 DOS 386 and XM, Multiuser DOS, DR DOS
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; -1.512946 (
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;
Digital Research (UK) Ltd., Charnham Park, Hungerford,
Berkshire, UK)) in Hungerford, Berkshire, UK.
As requested by several OEMs Digital Research started to plan
develop a new
DOS operating system addressing the shortcomings left by
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
DOS 3.31 with large disk support (
FAT16B a.k.a. "BIGDOS").
DR DOS 3.31 reported itself as "
DOS 3.31", while
the internal B
DOS (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 were
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.
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 (B
DOS 6.0, 1988-08-17, OEM only), 3.33 (B
1988-09-01, OEM only), 3.34 (B
DOS 6.0, OEM only), 3.35 (B
1988-10-21, OEM only), 3.40 (B
DOS 6.0, 1989-01-25), 3.41 (B
1989-06, OEM and retail). Like MS-DOS, most of them were produced in
several flavors for different hardware. While most OEMs kept the
DOS name designation, one OEM version is known to be called
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 BDOS
6.4 kernel. (Version 4 was skipped to avoid being associated with the
relatively unpopular MS-
DOS 4.0.) This introduced ViewMAX, a GEM-based
GUI file 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
IBMDOS.COM (for the B
DOS kernel), and the OEM label in
boot sectors was changed to "IBM␠␠3.3".
Front and rear views of the
Carry-I book-size 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
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).
DR 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
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 extra memory.
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 DR
DOS 6.0, code-named "Buxton".
DR DOS 6.0, while already at B
DOS level 6.7 internally,
would still report itself as "
DOS 3.31" to normal 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
DR 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
DOS in the multi-user products line), which would run
DOS applications in pre-emptively multitasked virtual
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 & Paste facility between
applications. Via the task-switcher API, graphical user interfaces
PC/GEOS could register as the task manager menu and
thereby replace the TASKMAX text mode menu, so that users could switch
between tasks from within a GUI.
Microsoft responded with MS-DOS 6.0, which again matched some
features of DR DOS 6.0.
Since December 1991 a pre-release version of Windows 3.1 was
designed to return a non-fatal error message if it detected a
Microsoft DOS. This check came to be known as the AARD code.
With the detection code disabled, Windows ran perfectly under
DOS and its successor Novell DOS. The code was present
but disabled in the released version of Windows 3.1.
In July 1992,
Digital Research Japan released DR
DOS 6.0/V, a Japanese
DOS/V compatible version of DR
DOS 6.0. A Korean version
appears to have been available as well.
Patching to counter Microsoft
It was a simple matter for
Digital Research to patch
DR DOS 6.0 to circumvent the AARD 'authenticity check' in
Windows 3.1 beta by rearranging the order to two internal tables in
memory (with no changes in functionality), and the patched version was
on the streets within six weeks of the release of Windows 3.1.
In 1992 Digital Research, still under its old name but already bought
Novell in July 1991, also embarked on a spin-off product code-named
"Merlin" and later released as
DOS 1, which, as its name
implies, was a very resource light DR
DOS 6.0 derivative aimed at the
emerging Palmtop/PDA market.
DOS was the first operating system in the family to sport the new
DOS 7.0 kernel with native
DOS compatible internal data structures
instead of emulations thereof. Replacing the
DOS emulation on top of a
CP/M kernel by a true
DOS compatible kernel helped a lot in improving
compatibility with some applications using some of DOS' internal data
structures and also was the key in reducing the resident size of the
kernel code even further - a particular requirement for the PDA
market. On the other hand, introducing a genuine Current Directory
Structure (CDS) imposed a limit on the depth of working directories
down to 66 characters (as in MS-DOS/PC DOS), whereas previous issues
DOS had no such limitation due to their internal organization of
directories as relative links to parent directories instead of as
absolute paths. Palm
DOS still reported itself as "PC
DOS 3.31" to
applications in order to keep the kernel small and not run into
compatibility problems with Windows, which would expect the DOSMGR API
to be implemented for any
DOS version since 5.0.
As well as a ROM-executing kernel, Palm
DOS had palmtop-type support
for features such as
PCMCIA PC Cards (with DPMS support), Power
BatteryMAX and the
$IDLE$ device driver with its patented
dynamic idle detection by Roger Gross and John Constant), MINIMAX
task switcher support for PIM (Personal Information Modules)
applications stored and executed from ROM via
PCMCIA stack for Palm
DOS was partially written by Ian Cullimore.
Contribution by Novell
This section needs additional citations for verification. Please help
improve this article by adding citations to reliable sources.
Unsourced material may be challenged and removed. (August 2011) (Learn
how and when to remove this template message)
Novell Corporation's name for DR-
DOS during the period
Novell sold DR-DOS, after the acquisition of
Digital Research in
1991. Regarding features and performance, it was
typically at least one release ahead of MS-DOS. In 1993, PC DOS
DOS 6.2 and PC
DOS 6.3 were trumped by Novell's
Novell CEO Robert Frankenberg's strategy included "major trimming",
selling off products like transactional database
Btrieve and killing
others such as
DOS and WordPerfect's multimedia Main Street
Novell licensed technology from Stac
Electronics for use in
DOS and its Network operating system,
Novell sold the product line off to Caldera on 23 July
1996, after it approached
Novell looking for a
DOS operating system to
bundle with its
DOS was described in
TechRepublic by John Sheesley as a failure.
Novell had bought
Digital Research with a view to using DR's product
line as a lever in their comprehensive strategy to break the Microsoft
monopoly. (This was part of a massive and ultimately disastrous
spending spree for Novell: they bought
WordPerfect Corporation at
about the same time, some of Borland's products, and invested heavily
Unix as well.) The planned DR
DOS 7.0, internally named "Panther",
intended to trump Microsoft's troubled MS-
DOS 6.0, was repeatedly
Novell was working on a Unix-like multi-user security
extension (compatible with its Multiuser DOS) and two new graphical
user interfaces (ViewMAX/3, a derivative of GEM, and "Star Trek", a
true port of Apple's System 7.1 to run under the new DR DOS
multitasker named "Vladivar").
DOS eventually arrived in December 1993 (with localized
versions released in March 1994), renamed
DOS 7 (a.k.a.
"NWDOS"), and without these three components, it was a disappointment
to some.[who?] 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,
OS/2 and 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 success.
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 US dollars.
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 Open
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 demonstrated at
CeBIT in March 1998,
and later, in a small team, developed into "WinBolt", both versions of
DR-DOS, which remained unreleased as of 2014[update], 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&Destroy virus scanner and FastBack Plus 2.0
utility, which previously came bundled with
Novell DOS. Instead it
brought an advanced version of NetWars.
Parts of Open
DOS 7.01 were released as open source in form of the
M.R.S. kit (for Machine Readable Sources) in May 1997, but with
licence terms mostly incompatible with existing open source licences.
The source was then closed again as Gross felt this would undermine
the commercial aspirations of the system.
After beta releases in September and November 1997, the next official
release came in December 1997, with the name changed to Caldera
DOS 7.02, soon followed by a further release in March 1998,
when the DR-
DOS name returned as Caldera DR-
DOS 7.02, now for the
first time written with a hyphen. Version 7.02 (now reporting itself
DOS 7.3) incorporated improved BIOS and B
DOS issues, developed by
Paul, adding many new boot and configuration options,
integrating many compatibility enhancements, bug-fixes and
optimizations for size and speed, and re-implementing all fixes of the
DOS updates. The BIOS improved the coexistence
DOS with Windows 9x and its support for third-party disk
compression drivers such as Microsoft's DriveSpace. It introduced a
diagnostics mode (activated by Scroll Lock), integrated debugger
support (with DEBUG=ON and a debugger loaded before or from within
CONFIG.SYS) and more flexible CONFIG.SYS tracing capabilities via the
F5/F6/F7/F8 hotkeys and the TRACE and TIMEOUT commands, thereby also
improving the integration of alternative command line shells such as
4DOS. Together with LOADER, SYS /DR:ext and the CHAIN
directive, it brought enhanced multi-configuration support for
DR/D/CONFIG.ext files and came with enhancements to the BASIC-like
CONFIG.SYS language for more powerful boot menus, convenient user
interaction and programmatical acting upon conditions (CPU386), return
codes and error levels (ERROR, ONERROR). It also allowed to change
the SCROLLOCK, CAPSLOCK, INSERT and VERIFY settings as well as the
SWITCHAR, YESCHAR, NOCHAR and RESUMECHAR characters. Various
behavioural details could be controlled with new parameters /Q, /L, /Y
and /S for SWITCHES. Further, it provided optional support for a LPT4:
device and allowed to configure the built-in COMx: and LPTx: devices
as well as to change the PRN: and AUX: defaults. The handling of
environment variables in CONFIG.SYS was improved and new load-high
facilities included such as the HIFILES/FILESHIGH and HIFCBS/FCBSHIGH
options to relocate file handles and FCB structures into UMBs, which
typically gave between 1 and 4 KB (and up to 15 KB) more free
conventional memory compared to previous versions, or the
HISHELL/SHELLHIGH SIZE directive to control the pre-allocation of HMA
memory for COMMAND.COM, which helped to avoid memory fragmentation and
thereby typically gave between 5 and 8 KB more continuous HMA memory
for HMA-capable third-party drivers to work with in conjunction with
third-party command line shells, which could not load into the HMA as
COMMAND.COM with its /MH option. At a reduced memory footprint version
7.02 also brought an enhanced NLS 4.xx sub-system by Paul to allow
multiple, distributed and possibly user-configured COUNTRY.SYS files
to be used by the system at the same time in a hierarchical
model. This also gave dynamic parser support for MS-DOS/PC DOS
COUNTRY.SYS file formats in addition to DR-DOS' own COUNTRY.SYS
formats, and it introduced support for the ISO 8601
international date format (including automatic detection) and the
then-new Euro currency. DR-
DOS 7.02 was fully Year 2000 compliant
and provided special support to work with buggy system BIOSes. It also
came with an updated FDISK, which could partition and format FAT32
volumes (but not yet work with LBA). The sources of the
for the external tools and drivers had meanwhile been found in Germany
and could thus be retro-fitted into the system as well, so that DR-DOS
7.02 finally not only caught up with
DOS 7, but was a true step
forward. The release was followed by various updates in June, August
and September 1998.
The updated internal B
DOS version number introduced a new problem:
some legacy third-party applications with special support for Novell
DOS, which were no longer being updated, stopped working. SETVER
DOS to disguise itself as
DOS versions by file
name and globally and, specifying a magic sub-version of 255, it would
even disable its own internal B
DOS version check in order to cope with
programs specifically probing for "DR-DOS". The modified kernel and
SETVER driver by Paul would, in an hierarchical model, also support
load paths in order to distinguish between multiple executables of the
same file name, and it introduced an extended mode, in which SETVER
could not only fake
DOS versions, but also B
DOS kernel versions.
Sub-versions of 128 to 255 would be reported as
DOS sub-versions 0 to
127 to applications, but with the B
DOS version check disabled, while
sub-versions 100 to 127 could be used to fake different B
DOS revision number (typically set to 0 in a static,
pre-boot patchable data structure) would be taken as the reported
sub-version instead, so that
SETVER /G /X 6.114 would allow versions
DOS since 7.02 to still report themselves as a "
DOS 6.0" and
with a faked B
DOS version 7.2 (114 decimal = 72 hexadecimal), thereby
DOS 7 / Open
While otherwise beneficial, the new HIFILES triggered a compatibility
problem in the DOS-UP feature of the third-party memory manager QEMM
8, which was hard-wired to expect a chunk of five handle structures in
conventional memory under DR-
DOS (as with previous versions up to
7.01), whereas version 7.02 by design left eight handles in low memory
when loading high files in order to maintain full compatibility with
older versions of Windows 3.xx. Compatibility with Windows for
Workgroups 3.11 had not been affected by this. A maintenance fix was
devised to patch a single byte in
IBMBIO.COM in order to switch the
behaviour and optionally re-invoke the old chunking. This freed some
150 bytes of conventional memory and enabled full compatibility with
DOS-UP, but at the same time broke compatibility with older versions
of Windows 3.xx when using the HIFILES feature, and vice versa. The
patch named IBMBIO85.SCR continued to work with newer versions of
In August 1998 the US-based
Caldera, Inc. created two new
subsidiaries, Caldera Systems, Inc. for the
Linux business, and
Caldera Thin Clients, Inc. for the embedded and thin-client
Another version, DR-
DOS 7.03 (still with B
DOS 7.3 and reporting itself
to applications as "PC
DOS 6.0" for compatibility purposes), was
pre-released at Christmas 1998 and then officially released on 6
January 1999 by Caldera UK. It came with significantly improved memory
managers (in particular enhanced DPMI support in conjunction with the
multitasker) and other enhancements, such as added DEVLOAD and DRMOUSE
utilities, but a changed OEM label in the boot sector of volumes
formatted under DR-
DOS could also cause problems under other operating
systems (which can be circumvented by NOVOLTRK). DR-
would become the last version of DR-
DOS also tailored for desktop use.
Caldera, Inc. wanted to relocate the DR-
DOS business into the US and
closed the successful UK operation in February 1999 after Gross
resigned and set up iCentrix to develop the MarioNet split web
browser. Development was then moved into the US (which never worked
out due to a total lack of expertise in this field at Caldera US), and
DOS line fell to its branch company, Caldera Thin Clients,
which was renamed Lineo, Inc. on 20 July 1999.
renamed EmBrowser and was said to be ported to Linux. Lineo
DOS 7.03 in June and September 1999, still branded as
"Caldera DR-DOS" and without any changes, but otherwise focussed
Linux for embedded systems, based on a stripped-down version of
OpenLinux named Embedix.
Among the latest and independently-developed versions of DR-
DOS 7.04 (as of 19 August 1999) and 7.05 (as of 30 November
1999), still branded as "Caldera DR-DOS". These were variants
of the system consisting only of the kernel and command shell. With a
specialized native implementation of
FAT32 and large hard disk support
they could be found bundled with Ontrack's Easy Recovery 5 in 2000,
replacing the dynamically-loadable DR
FAT32 redirector driver, which
still came with Easy Recovery 4. They were also used for Seagate
Technology's SeaTools and the CD imaging software Nero Burning
ROM. While still reporting a B
DOS 7.3 internally, these were the first
versions to report themselves as "PC
DOS 7.10" to applications in
order to indicate integrated
FAT32 support. Designed to be mostly
backwards-compatible, the DR-
IBMBIO.COM could be
combined with the DR-
IBMDOS.COM in order to give the
DOS 7.03 kernel LBA capabilities and work with
drives larger than 8 GB. For specific OEM requirements, DR-
DOS 7.06 by
Wightman combined the kernel files into a single binary executable, so
that, similar to IO.SYS of Windows 98, it could be booted by MS-DOS
7.10 boot sectors (but no longer by DR-
DOS boot sectors). DR-
DOS 7.4/7.7) by Paul introduced new bootstrap loaders and
updated disk tools in order to combine support for CHS and LBA disk
access, the FAT12,
FAT32 file systems, and the differing
bootstrapping conventions of DR-DOS, PC DOS, MS-DOS, Windows, REAL/32
and LOADER into a single MBR and boot sector, so that the code would
continue to load any version of DR-
DOS down to 3.31 (and since DR-DOS
7.04 also with
FAT32 support), but could also be used to launch the PC
DOS or MS-
DOS system files, including those of Windows 9x and PC DOS
7.10. At the same time the kernel could not only be booted by the new
sectors, but also by any previously DR-
DOS formatted disks, as well as
off disks with existing PC
DOS or MS-
DOS boot sectors and a variety of
other boot-loaders, thereby easing the coexistence and setup of
multi-boot scenarios in conjunction with other operating systems.
Lineo was bought out, and some of Lineo's former managers
purchased the name and formed a new company, DRDOS, Inc. dba
DeviceLogics L.L.C. They have continued to sell DR-
DOS for use in
embedded systems. DR-
DOS 8.0 was released on March 30, 2004 featuring
FAT32 and large disk support, the ability to boot from ROM or Flash,
multitasking and a DPMI memory manager. This version was based on the
kernel from version 7.03. The company later released DR-
FAT32 support) in autumn 2005. This version was instead
based on Open
DOS 7.01.xx. Both 8.0 and 8.1 were withdrawn.
Aside from selling copies of the operating system, the DRDOS, Inc.
website lists a buyout option for DR-DOS; the asking price is
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,
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
DOS operating systems
DOS operating systems
^ The rest of the story: How Bill Gates beat Gary Kildall in
OS war, Part 1 ScobleShow: Videoblog about geeks, technology, and
^ Borreson, Nan, ed. (March 1984). "PC-Mode bridges
CP/M and PC-DOS".
Digital Dialogue - Employee Newsletter of
Digital Research Inc.
Digital Research. 3 (1): 3. Archived from the original on 2017-09-10.
Retrieved 2017-09-10. 
^ Borreson, Nan, ed. (May 1984). "Concurrent
DOS bridges PC-DOS,
Digital Research News - For
Digital Research Users Everywhere.
Digital Research. 4 (2): 3. Archived from the original on 2017-09-10.
Retrieved 2017-09-10. 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 DR DOS
operating system out of market Caldera News, 1996-07-24 ().
^ Ponting, Bob (1988-08-15). "Award Software plans to implement
Digital Research's OS on ROM chip". Infoworld. Retrieved
Caldera, Inc. (1997). Open
DOS Developer's Reference Series —
DOS Multitasking API Guide — Programmer's Guide. Printed in the
UK, August 1997. Caldera Part No. 200-DOMG-004 ().
^ The AARD Code
^ Dr. Dobb's Journal investigation
^ "Timeline of
DOS/V versions" (in Japanese). 2014-11-28. Retrieved
^ Tam, Roy; Elliott, John (2014-01-12). "DR
DOS 6.0/V". Retrieved
2017-01-16. (NB. Has screenshots of a DBCS-enabled version of
ViewMAX/2 running on DR
DOS 6.0/V and a hex dump of the corresponding
DRFONT database SCREENHZ.FNT for its $FONT.SYS.
^ CW (1992-09-11). "Markt für Desktop-Betriebssysteme im Visier -
Novell kündigt die ersten Low-end-Produkte mit dem Betiebssystem DR
DOS 6.0 an".
Computerwoche (in German). Munich, Germany: IDG Business
Media GmbH. Archived from the original on 2017-07-04. Retrieved
^ Hildebrand, J. D. (2011-12-19). "
Microsoft trial ends in
hung jury". SD Times. Retrieved 2012-03-02.
Novell DOS". PC Magazine. Retrieved 2012-03-02.
^ Scott, Karyl (1991-07-29). "Novell/DRI merger to reap better client
management". InfoWorld: 33. Retrieved 2017-01-21.
^ Allchin, Jim (1992-05-27) [1991-07-17]. "Novell/Digital Research
reach definitive agreement..." (PDF) (Court document). Plaintiff's
exhibit 828, Comes v. Microsoft. Archived (PDF) from the original on
2016-11-19. Retrieved 2017-01-21.
^ Fisher, Lawrence M. (1994-07-24). "The Executive Computer;
Microsoft's Operating System Rivals Get a Boost, Sort Of". The New
York Times. Retrieved 2012-03-02.
^ Anthony, Sebastian (2011-07-27). "MS-
DOS is 30 years old today".
ExtremeTech. Retrieved 2012-03-02.
^ Fisher, Lawrence M. (1995-09-18). "
Novell Readies a Response to
Windows". The New York Times. Retrieved 2012-03-02.
^ Fisher, Lawrence M. (1994-03-06). "The Executive Computer; Will
Users Be the Big Losers in Software Patent Battles?". The New York
Times. Retrieved 2012-03-02.
^ Sheesley, John (2008-04-09). "My
DOS version can beat up your DOS
version". TechRepublic. Retrieved 2012-03-02.
^ a b Susman, Stephen D.; Eskridge III, Charles R.; Susman, Harry P.;
Southwick, James T.; Folse III, Parker C.; Borchers, Timothy K.;
Palumbo, Ralph H.; Harris, Matthew R.; Engel, Lynn M.; McCune, Philip
S.; Locker, Lawrence C.; Wheeler, Max D.; Hill, Stephen J.; Tibbitts,
Ryan E. (May 1999). "In the United States District Court - District of
Utah, Central Division -
Caldera, Inc. vs.
Microsoft Corporation -
Case No. 2:96CV 0645B - Caldera, Inc.'s Memorandum in opposition to
defendant's motion for partial Summary Judgment on plaintiff's
"Technological Tying" claim" (Court document). Caldera Inc. Archived
from the original on 2013-10-03. Retrieved 2013-10-05.
^ BBC News BUSINESS Caldera vs
Microsoft - the settlement
^ "Exhibits to Microsoft's Cross Motion for Summary Judgment in Novell
WordPerfect Case". Groklaw. 2009-11-23. Retrieved 2011-10-22.
^ Company Data Rex: Basic information about company Caldera (UK)
Limited. Company Number 03252883, Record as of 2001-07-01 ().
^ a b Lea, Graham (1998-03-23). "Cebit: Caldera shows Windows on
DR-DOS, denying MS claims". Cebit news. Hanover, Germany. Retrieved
^ Mike Romano. The mouse that roared. Forget the feds. It's up to an
obscure Utah company to prove what we already know: that
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."
^ Paul, Matthias (1997-07-30). NWDOS-TIPs — Tips & Tricks rund
DOS 7, mit Blick auf undokumentierte Details, Bugs und
Workarounds (e-book). MPDOSTIP (in German) (3, release 157 ed.).
Archived from the original on 2017-09-10. Retrieved 2014-08-06.
NWDOSTIP.TXT is a comprehensive work on
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
^ a b c d e f g Paul, Matthias (1997-10-02). "Caldera OpenDOS
7.01/7.02 Update Alpha 3
IBMBIO.COM README.TXT". Archived from the
original on 2003-10-04. Retrieved 2009-03-29.
^ a b Ralf D. Brown. Ralf Brown's Interrupt List, INTER61 as of
2000-07-16 (), entry for DR-
DOS version check under INT
^ Brothers, Hardin; Rawson, Tom; Conn, Rex C.; Paul, Matthias; Dye,
Charles E.; Georgiev, Luchezar I. (2002-02-27). 4
DOS 8.00 online
^ a b c d Paul, Matthias (2001-06-10) . "
DOS COUNTRY.SYS file
format" (COUNTRY.LST file) (1.44 ed.). Archived from the original on
2016-04-20. Retrieved 2016-08-20.
^ Paul, Matthias (2001-06-10) . "Format description of DOS,
Windows NT .CPI, and
Linux .CP files" (CPI.LST file) (1.30
ed.). Archived from the original on 2016-04-20. Retrieved
^ Paul, Matthias (2001-06-10) . "Overview on DOS, OS/2, and
Windows codepages" (CODEPAGE.LST file) (1.59 preliminary ed.).
Archived from the original on 2016-04-20. Retrieved 2016-08-20.
^ Pamela Jones: Caldera, Inc./Caldera Systems, Inc. 1998 Asset
Purchase and Sale Agreement. Groklaw Blog, 2004-02-29 ().
^ Caldera. Caldera creates two wholly-owned subsidiaries.
Press-release, 1998-09-02, PR-Newswire ().
^ Paul, Matthias (2002-02-20). "Need
DOS 6.22 (Not OEM)".
alt.msdos.programmer. Archived from the original on 2017-09-09.
^ Paul, Matthias (2004-08-25). "NOVOLTRK.REG". www.drdos.org. Archived
from the original on 2016-03-04. Retrieved 2011-12-17.
^ 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 ().
^ FREE SOFTWARE FOR
DOS — Operating Systems
^ a b http://www.freedos.org/freedos/news/press/2005-drdos.txt
DOS Buy Out DR
DOS Embedded DOS
^ Welcome to the DR-DOS/Open
DOS Enhancement Project!
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.).
Digital Research, Inc. Part Number 1176-2004-002. (501 pages)
Digital Research, Inc. (May 1990).
ViewMAX User Guide (1st ed.).
Digital Research, Inc. Part Number: 1174-2004-002. (88 pages)
Digital Research, Inc. (August 1990). DR
DOS 5.0 Release Notes.
Digital Research, Inc. Part Number: 1176-1001-002. (11 pages)
Digital Research, Inc. (August 1991). DR
DOS 6.0 Software performance
Digital Research, Inc. Part No. 000-1200-00. (A5 – 1
Digital Research, Inc. (August 1991). DR
DOS 6.0 User Guide (2nd ed.).
Digital Research, Inc. Part Number. 1182-2004-002. (698 pages)
Digital Research, Inc. (August 1991).
ViewMAX User Guide (2nd ed.).
Digital Research, Inc. Part Number. 1192-2054-002. (106 pages)
DOS 7 online