DR-DOS

(Enhanced) DR-DOS

File:DR-DOS-8.PNG
Developer	Originally by Digital Research, now developed by DRDOS, Inc. and The DR-DOS/OpenDOS Enhancement Project
OS family	DOS
Working state	Current
Source model	Mixed - partly Closed source, partly Open Source
Latest release	DR-DOS 8.1, Enhanced DR-DOS 7.01.07 / Oct 2005, Mar 2005
Kernel type	Monolithic kernel
Default user interface	CLI, GUI available separately
License	Proprietary
Official website	DRDOS, Inc. / The DR-DOS/OpenDOS Enhancement Project

DR-DOS is a DOS-type operating system for IBM PC-compatible personal computers, originally developed by Gary Kildall's Digital Research and derived from CP/M-86.

History

Origins in CP/M

Digital Research's original CP/M for 8-bit 8080, Z-80, and 8085 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 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 operation system, 86-DOS, from Seattle Computer Products. This became Microsoft MS-DOS and IBM PC-DOS. 86-DOS' command structure and application programming interface imitated that of CP/M. Digital Research threatened legal action, claiming PC/MS-DOS to be too similar to CP/M. IBM settled by agreeing to sell their x86 version of CP/M, CP/M-86, alongside PC-DOS. However, PC-DOS sold for $60, while CP/M-86 had a $240 price tag. The proportion of PC buyers prepared to spend four 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 favour, was only temporary.

Digital Research fought a long losing battle to promote CP/M-86, and eventually decided that they could not beat the Microsoft-IBM lead in application software availability, so they modified CP/M-86 to allow it to run the same applications as MS-DOS and PC-DOS. Initially, they sold DOS Plus, which ran applications for both platforms. It did not perform well, and Digital Research made another attempt, this time a fully DOS system. The new disk operating system was launched in 1988 as DR-DOS.

First DR-DOS version

The first version was released in May, 1988. Version numbers were chosen to reflect features relative to MS-DOS; the first version promoted to the public was DR-DOS 3.41, which offered features comparable to the successful MS-DOS 3.3 and its derivatives.

At this time, MS-DOS was only available bundled with hardware, so DR-DOS achieved some immediate success as it was possible for consumers to buy it through normal retail channels. Also, DR-DOS was cheaper to license than MS-DOS. As a result, DRI was approached by a number of PC manufacturers who were interested in a third-party DOS, and this prompted several updates to the system.

Further information: Comparison of x86 DOS operating systems

Version 5.0

DR-DOS version 5.0 was released in May 1990. (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, and bundled disk-caching software, and also offers vastly improved memory management.

First, the DR-DOS kernel and structures such as disk buffers can be located in the High Memory Area (HMA), the first 64KB 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 640KB of the PC's RAM – the area in which all MS-DOS applications run.

Additionally, on 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 was the first DOS to integrate such functionality into the base OS (loading device drivers into upper memory blocks was possible using QEMM and MS-DOS). As such, on a 386 system, it could offer vastly 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 400KB of free conventional memory – too little to run most late-1980s software. DR-DOS 5, with a small amount of 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 620KB out of the 640KB.

Because DR-DOS leaves so much conventional memory available, some programs fail to load as they start "impossibly" low in memory – inside the first 64KB. DR-DOS 5's new LOADFIX command works around this by leaving a small empty space at the start of the memory map.

Competition from Microsoft

Faced with substantial competition in the DOS arena, Microsoft responded strongly. They announced the development of MS-DOS 5.0 in May 1990, to be released in 1991 and include similar advanced features to those of DR-DOS. It included matches of the DR's enhancements in memory management.

DR responded with DR-DOS 6.0 in 1991. This bundled in SuperStor on-the-fly disk compression, to maximise available hard disk space. DR-DOS 6.0 also includes an API for multitasking on CPUs capable of memory protection, namely the Intel 80286 and newer. The API was available only to DR-DOS aware applications, but well-behaved ordinary DOS applications can also be pre-emptively multitasked by the bundled task-switcher, TaskMax. On 286-based systems, which only allow a single process to execute simultaneously, DOS applications are suspended to the background to allow others to run.

Microsoft responded with MS-DOS 6.0, which again matched some features of DR-DOS 6.0.

Though DR-DOS was apparently 100% binary compatible with applications written for MS-DOS, Microsoft nevertheless expended considerable effort in attempts to break compatibility. In one example, they inserted code into a beta version Windows 3.1 to return a non-fatal error message if it detected a non-Microsoft DOS. This check came to be known as the AARD code. With the detection code disabled, Windows ran perfectly under DR-DOS and its successor Novell DOS. The code was present, but disabled in the released version of Windows 3.1

PalmDOS

At about this time Digital Research also embarked on a spin-off Product called PalmDOS (and later released as Netware PalmDOS), which as its name implies was a DR-DOS derivative aimed at the emerging Palmtop/PDA market.

As well as a ROM-executing kernel it had palmtop-type support for features such as PCMCIA PC Cards, Power Management, etc.

Hungerford/Monterey

Although DRI was based in Monterey, California, most of the operating system work (especially DR-DOS, Multiuser DOS and PalmDOS) was done in Hungerford, UK.

Patching to counter Microsoft

It was a simple matter for Digital Research to patch DR-DOS to circumvent the 'authenticity check' in Windows 3.1 beta, and the patched version was on the streets within six weeks of the release of Windows 3.1. With improved marketing and packaging, very advanced memory management, disk compression and the Super PC-Kwik caching software, DR-DOS 6.0 was an outstanding value and easily the most successful version.

Around this time, networking giant Novell 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 in Unix as well.) The planned DR-DOS 7.0, intended to trump Microsoft's troubled MS-DOS 6.0, was repeatedly delayed. When it eventually arrived – renamed to Novell DOS 7.0 – it was a disappointment. It was bigger and introduced many new bugs and the main functional addition was Novell's second attempt at a peer-to-peer networking system, Personal Netware. This worked and was better than its predecessor Netware Lite 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.

Contribution by Novell

File:Novell DOS 7 manual cover.png

Novell DOS 7 required several bug-fix releases and was not completely stable when the next development occurred. Realising eventually that their formidable networking skills did not translate into other areas, Novell sold the product line off to Caldera Systems in 1996, by which time it was of little commercial value.

After Novell

Caldera released the operating system as open source, under the name "Caldera OpenDOS". OpenDOS was released as version 7.01 and 7.02, and the source was then closed. (Version 7.02 was called "Caldera OpenDOS 7.02" while in beta testing; by the time it was released in December of 1997, it was branded "Caldera DR-OpenDOS 7.02". The next release came in March of 1998; it was branded "Caldera DR DOS 7.02") Another version was released, 7.03, before Caldera transferred the DR DOS line to a branch company, Caldera Thin Clients, which would become Lineo. Lineo would later release revisions of 7.03, still branded as "Caldera DR DOS"

The last Lineo version was DR DOS 7.04/7.05, still branded as "Caldera DR DOS". This was an embedded system consisting only of the kernel and command shell. It was built for Seagate Technology's Seatools, with a buggy implementation of FAT32 and large hard disk support.

The Microsoft Lawsuit

Although DR-DOS had ceased to be a significant present threat to their market share by 1995, Microsoft now faced growing competition from IBM's PC-DOS 6.3, and 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 law suit brought in Salt Lake City by Caldera. Microsoft lawyers tried repeatedly to have the case thrown out 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 for an undisclosed sum.

Recent versions

The OpenDOS 7.01 source code is still actively being developed by The DR-DOS/OpenDOS Enhancement Project, founded in July 2002 in an attempt to bring the functionality of DR-DOS up to parity with modern PC operating systems. The project's efforts have resulted so far in adding native support for large disks (LBA) and the FAT32 filesystem. There were also several other enhancements, including improved memory management and support for the new FAT+ filesystem extension which allows files of almost 256 GB in size on normal FAT partitions.

In 2002, Lineo was bought out, and some of Lineo's former managers purchased the name and formed a new company, DeviceLogics. They have continued to sell DR-DOS for use in embedded systems. DR-DOS 8.0 was released on 30 March 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 then split into Devicelogics Inc. and DRDOS Inc, which released DR-DOS 8.1 (with better FAT32 support) in autumn 2005. This version was not based upon version 8.0, but was a complete rewrite. Both 8.0 and 8.1 have now been pulled (because of the discoveries outlined below), and replaced with Caldera DR DOS 7.03.

Aside from selling copies of the operating system, the DR DOS Inc. website lists a buyout option for DR DOS; the asking price is $25,000.

Current Versions:

• Enhanced DR-DOS 7.01.08 WIP (8.2.2008) (open source; under active development)
• DRDOS Inc.'s DR-DOS 7.03 (closed-source; no visible development occurring)

Controversies

In October 2005, it was discovered that DR-DOS 8.1, included several utilities from FreeDOS and Enhanced DR-DOS, and the kernel was a patched form of the FreeDOS kernel. DR-DOS Inc. failed to comply with the GNU General Public License (GPL) by not crediting these to their authors and including the source code. Following complaints from FreeDOS developers, DR DOS Inc. pulled all 8.x versions from their website.

See also

• Comparison of x86 DOS operating systems
• CP/M
• MP/M
• DOS Plus
• OpenDOS
• Multiuser DOS

External links

• Official DR-DOS site
• Enhanced DR-DOS/OpenDOS Project
• Enhanced DR-DOS Forum
• Dr-DOS Wiki
• Graphic Dr-DOS 7.03 Project (with Graphic Browser) on a single bootable floppy disk for children