SvarDOS: a modern incarnation of DOS with open source code and repository

American Gary Arlen Kildall, together with his wife, founded the company Intergalactic Digital Research, later Digital Research, Inc — not to be confused with Digital Equipment Corporation. His operating system CP/M gained immense popularity at the time and sold over a quarter of a million copies. Today we will discuss how the long-standing brainchild of this programmer suddenly developed in the modern world and how retrocomputing enthusiasts decided to create their own open-source version of DOS.

A Look into the Past

The year is 1972. Gary Kildall buys himself an Intel 4004 processor, which was released less than a year ago, and is actively experimenting with its programming. To put it simply, it's like buying an ATmega328 or ESP32 microcontroller today and trying to write software for it. But back then it was real hardcore. No visual editors or high-level programming languages. Here's an assembler, a very limited set of instructions, four kilobytes of available memory — have fun.

Gary quickly realized that at the very least, a programming language was needed for all this magnificence, because writing in pure assembler is difficult and time-consuming. Rolling up his sleeves, he wrote the procedural language PL/M, or Programming Language for Microcomputers. This immediately solved a lot of problems, lowering the entry threshold for development. But this was only the beginning, the first important step towards creating the new CP/M operating system.

CP/M was deciphered as Control Programs for Microcomputers, and this fully revealed its purpose. By the second half of the 70s, it became the most popular OS for microcomputers on Intel 8080 and Zilog Z80 processors. At that time, CP/M had no competitors — exactly until the moment when microcomputers began to be replaced by personal PCs.

I will not retell the whole story of Gary's struggle with such monsters as Microsoft and IBM, so as not to repeat myself. All this has long been here, on tekkix. From this whole story, one important fact can be traced — CP/M formed the basis of both MS-DOS and Digital Research's own development, DR-DOS. These two operating systems ran parallel courses and until 1991 were even actually compatible with each other. After 1991, Microsoft took the lead, and DR-DOS began to be forgotten, as it was no longer compatible with the first versions of Windows.

Ultimately, DR-DOS was sold to the well-known company Novell, which had long been developing systems on CP/M. The latter immediately abandoned the original name, renaming DR-DOS to Novell DOS. For some time, development did continue and two new versions, Novell DOS 6 and 7, were released. But then it was decided to abandon further development.

There are many reasons for this: from the dominance of MS-DOS and the emergence of Windows to the need to focus on network technologies for NetWare. So the rights to Novell DOS were sold to Caldera Systems, which later became the infamous The SCO Group. It acted quite interestingly, renaming the operating system to OpenDOS again, and continued development, fixing many bugs in version 7. But most importantly, the OS source code was opened for non-commercial use, which allowed enthusiasts to create their own developments based on OpenDOS.

The ordeal for Kildall's brainchild did not end there. Caldera Systems was split into three different companies, and the rights to OpenDOS were transferred to one of them — Lineo. Without much thought, it renamed the OS again, returning it to its original name DR-DOS, and continued development, focusing on embedded systems. The calculation was quite understandable: most of these systems had severely limited resources, and the compact DR-DOS fit perfectly into this landscape.

Lineo released two more versions of the operating system, which inherited the open-source code (DR-DOS 7.02 and 7.03). What do you think happened next? Correct — the rights were sold again, this time to DeviceLogics (later DRDOS, Inc). They did not bother with another renaming, but released DR-DOS 8, again under a commercial license and with closed source code. They successfully sold DR-DOS until 2018, after which they quietly went offline.

One could put a period in the history of DR-DOS here, but the modern world is good because it is full of enthusiasts. Since OpenDOS was released with open-source code, any developer could fork it and "raise the fallen banner." This is what happened — SvarDOS was born.

How to install SvarDOS

The installation distribution of SvarDOS is available in three versions:

• Stable build, distributed as a CD-ROM ISO image and sets of floppy disk IMG images (from 360K to 1.44M). Bonus — a file for a USB flash drive.

• BNS build is only available as an ISO image, intended for people with disabilities. This distribution includes PROVOX, a screen reading application that allows blind people to easily install and use SvarDOS. It also supports connecting the Braille 'n Speak device — a portable device that combines a Braille keyboard and a speech synthesizer.

• Bleeding-edge version is available, like Stable, in all possible options. But it is worth remembering that this is essentially an alpha version, which can be buggy in any way.

And for those who are interested in looking at the source code and possibly participating in the development themselves, there is a Subversion repository:

svn co svn://svn.svardos.org/svardos svardos

Interestingly, SvarDOS is developed using a rolling-release model. Instead of releasing specific versions, builds are uploaded as they become ready, allowing you to always use the latest version of the OS at the time of download. The main platforms targeted by SvarDOS are retro computers released from 1980 to 2000. However, nothing prevents you from installing it as a virtual machine for the same VirtualBox.

The installer greets us with a language selection, where unexpectedly there is Russian. Next, the system will prompt you to choose a keyboard layout. And there, too, the Russian language is supported:

However, everything was translated using, apparently, Google Translate, which is clearly visible on the next screen:

It would seem that everything is fine, and you need to click Install SvarDOS, but remember that we have a clean and unpartitioned disk. So, we need to first create a partition table on it using FDISK:

And only now, having used the same items again, can we proceed with the installation. We are greeted by a small disk selection window:

Next, the system will automatically determine that the disk is not formatted and will offer to do so:

If you look at SvarDOS globally, the main goal of this project was to make the use of DOS more convenient and accessible, both for "retro hardware" and for various emulators (and devices based on them). The main feature of SvarDOS is the presence of a package manager and its own repository, which allows you to directly install packages into the system. This repository is available not only from the network, but also locally in the form of an ISO image.

This approach allows you to easily install various applications on devices that, for various reasons, do not have access to the network. You can install the desired program using the command:

C:\> PKG INSTALL PACKAGE.SVP

To work with the network repository, there is a PKGNET command, which significantly simplifies the delivery of packages to the target machine. By default, SvarDOS supports all the commands of regular MS-DOS and is capable of running all the same applications. At the same time, the developers focused on improvements related to memory management and compatibility with a large amount of hardware.

Of course, SvarDOS is not the only distribution that sets itself a similar task. Its main opponent is the FreeDOS project, which first appeared in 2006. The latter releases approximately every five years. Even though DOS is generally only of interest to enthusiasts now, such a gap between releases seems too long. SvarDOS with its rolling-release approach is more attractive in this regard.

Again, FreeDOS has taken the path of including only free software in its composition. This imposes restrictions on what packages will be in the distribution as a result. SvarDOS is more liberal in this regard. Packages that enter the repository must meet four simple criteria:

• be useful to users;

• have decent quality;

• be free;

• possibility of legal distribution in the form of repackaged packages.

Thus, if some software meets these criteria, then you can assemble an SVP package (a ZIP archive with additional metadata and installation and removal scripts) from them and send it to the public repository.

Finalizing

The next reincarnation of DR-DOS under the wing of retrocomputing enthusiasts has already interested many. Especially considering that everyone can make their own contribution to the project: fix a bug or translate something. Or maybe even add support for some rare hardware. I'm sure any help will come in handy.

For me personally, the appearance of SvarDOS was another reminder that there are many people among us who not only love retrocomputers. They are ready to invest in ensuring that the efforts of programmers from the past are not in vain.

What do you think, will SvarDOS be able to achieve its goals? We look forward to your comments.