Free Software for DOS
Operating Systems

21 Aug 2006

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FreeDOS — Free MS-DOS clone with many improvements.

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[updated 2006-03-14]

"The to create a free implementation of MS-DOS" that "Works on old hardware, in DOS emulators, and in embedded systems." Some components can be plugged into any DOS. With many new and enhanced functions, and an impressive array of addons, this DOS is worth serious attention.

Authors: The many contributors to the FreeDOS Project, founded and coordinated by Jim Hall.

2005-11-30: Beta 9 Service Release #2.

Go to the FreeDOS Project's home page for news, info and downloads.

Linux users: See DOSEMU, further down this page, for a variant of this OS.

Also worth visiting is FreeDOS-32, a project "to provide a heavily modularized framework to enable features that legacy DOS systems don't have, like 32-bit flat memory model, optimized I/O, support for many file systems, compatibility layers, support for modern standards..."

ROM-DOS — Fully compatible DOS, runs from disk or ROM.

* * * * *

[added 2006-08-21]

ROM-DOS was originally developed to run from ROMs in handheld computers and other embedded systems, but it also runs from a floppy or fixed disk. The main download package contains versions 6.22 and 7.1. Both are compatible with other DOSes that have similar version numbers, but with added features: Full support for FAT32/LBA hard disks and Long File Names (up to 260 chars), ZModem file transfer, TCP/IP stack, and much more. Free for personal use.

Runs on Intel 80186+, NEC V-series, and other compatible CPUs. ROM-DOS can be used as the base for Win3.x/9x, and as the secondary command processor under any Windows.

Author: Datalight, Inc. (2006).

2006-04-12: v7.10 Revision 4.20.1588SU.

Go to Datalight's ROM-DOS page, and register or sign in (free, requires email address only). Then go to Resources and download the Single User Version (4.3MB), which includes v6.22, v7.10, diskette image, and manual. Also available are the Single User Network Add-on (1.9MB), and many docs that supplement the manual in the main package.

DR-DOS and OpenDOS 7.01 / 7.02 / 7.03 — The Digital Research-Novell-Caldera-Lineo DOSes, now free.

* * * *

[updated 2005-06-22]

DR-DOS, direct descendant of Digital Research's CP/M, the first OS for microcomputers, has been upgraded and expanded to compete very well against other DOSes for the PC. Variants of it support for large FAT32 multi-partition hard disks, networking, 80386 protected mode services, and more. And it works with Windows 3.x!

A very brief (and possibly confusing) business history: Digital Research developed DR-DOS up to v6.0, then sold it to Novell, Inc., which renamed it Novell DOS, and then developed it up to v7. The next owner, Caldera Systems (now part of The SCO Group, Inc.) renamed it OpenDOS and released v7.01 and v7.02. Ownership next passed to Lineo (originally Caldera Thin Clients, and now Metrowerks), which changed the name OpenDOS 7.02 to DR-DOS 7.02, and then released v7.03. The current owner, DRDOS, Inc. (formerly Devicelogics, Inc.) sells bootable and embedded variants of v7.03.

Novell Caldera Lineo DRDOS, Inc.
DR-DOS 6 Novell DOS 6

Novell DOS 7 OpenDOS 7.01

OpenDOS 7.02 DR-DOS 7.02

DR-DOS 7.03 DR-DOS 7.03

Binaries for three versions are free for private, non-commercial use, in the packages listed below.

OpenDOS 7.01 is available in two bundles: Full, with Personal NetWare (PNW) and NetWareClients (NWC); and Lite, without PNW/NWC. Each bundle is available in a package of single files for installing from HD or CD, as 1.2MB diskette images, as 720K diskette images, and as 1.44MB diskette images – a total of eight packages:

Full, HD or CD installer
Lite, HD or CD installer
Full, 1.2MB diskette images
Lite, 1.2MB diskette images
Full, 720K diskette images
Lite, 720K diskette images
Full, 1.44MB diskette images
Lite, 1.44MB diskette images
DR-DOS 7.02 is available ten ways:
Full, HD or CD installer
Lite, HD or CD installer
Full, 1.2MB diskette images
Lite, 1.2MB diskette images
Full, 720K diskette images
Lite, 720K diskette images
Full, 1.44MB diskette images
Lite, 1.44MB diskette images
Full, five 1.44MB diskette image files
Lite, three 1.44MB diskette image files
DR-DOS 7.03 is available three ways:
Full, HD or CD installer
Full, five 1.44MB diskette image files
Lite, three 1.44MB diskette image files

Also available are FAT32 & LFN drivers, and other OS and PNW support files. For antique collectors, there is CP/M 2.2. Source code (C, ASM) for OpenDOS 7.01 is free for evaluation, educational and non-profit use (see Enhanced DR-DOS, next article, for download location).

Download sites
Planet Mirror
The Horde Project
University of Bayreuth
Free Software Network
US *
  * = 7.01 not available

Florian Xaver's Salamander - the Club of Dr-DOS has tools, info and links to even more DOSes.

Christoph Fuchs's Unofficial DR-DOS Resources has the complete DR-DOS documentation library, other info and tools.

The new Digital Research has CP/M manuals and other info.

Enhanced DR-DOS — Updated, open source derivative of the Digital Research-Novell-Caldera OS.

* * * *

[added 2004-10-29, updated 2006-03-14]

Enhanced DR-DOS is based on Caldera OpenDOS 7.01, with integrated modern features: FAT32/FAT+/LBA disk and LFN support, better memory management, file sizes up to 256GB, & more. This is the only member of the DR-DOS / OpenDOS family that is still in development. Requires the original OpenDOS 7.01, which it patches.

From the author:
Like other, similar projects, it strives to achieve compatibility with most existing software written for DOS. Unlike these, however, it will not stop there. The long-term goal will be to gradually evolve DR-DOS into a modern PC operating system with all features that one would expect of one of these...

Enhanced DR-DOS is available as compiled binaries, which can be dropped into an OpenDOS 7.01 installation kit. Source code is also available, with utilities to aid in patching the original OpenDOS 7.01 source. Note: This version of DR-DOS/OpenDOS is used because it is the only one for which the source code is free.

Author: Udo Kuhnt, Germany (2005-2006).


Latest stable release
7.01.08 WIP
Revised work-in-progress for testing

Go to The DR-DOS/OpenDOS Enhancement Project for complete info & downloads of all components.

OpenDOS 7.02-4 — DOS under DOSEMU and Linux.


[added 2004-12-19, updated 2005-06-23]

This variant of OpenDOS 7.02 provides a full DOS under Caldera OpenLinux with DOSEMU, which it configures. It should work easily with other flavors and relatives of Red Hat Linux (OpenLinux was one), and later DOSEMU. Distribution files are HD images that contain gzipped .cpio files.

Author: Caldera Thin Clients, Inc. (1999).


DR-DOS 7.04 / 7.05 — A DR-DOS that manages FAT32 & LBA hard drives.


[added 2005-06-22, updated 2006-08-21]

DR-DOS 7.04 / 7.05 was originally developed by Ontrack Data Recovery in 1999 for use on bootable diskettes. It supports FAT32/LBA hard drives, and drives larger than 8.4GB, without external drivers, and has been used by Ontrack and by Seagate Technology with diagnostic and recovery tools, and by IBM with installers.

DR-DOS 7.04 / 7.05 is not a complete OS, but consists only of the three kernel files. The double version number reflects the differing file IDs: IBMBIO.COM and IBMDOS.COM are labeled internally as 7.04; COMMAND.COM is labeled as both 7.04 and 7.05, but is reported on bootup and by VER as 7.05 only.

Despite the limited original purpose, the files can be installed on a system hard drive as part of a complete OS: Doing so is as simple as overwriting a DR-DOS 7.03 installation with the new files.

Caution: There may be incompatibilities between 7.04 / 7.05 and some external programs. When two or more hard disks are in use, drive letter assignments might change. Test well! (And think about going to Enhanced DR-DOS or FreeDOS instead, with the same disk handling but better system integration, and other new features).

Bug: The RENAME command does not work. But help is available – see next article.

Kernel files
Installer EXE, creates 1.44MB boot diskette with kernel files

A fix for the RENAME bug in OEM DR-DOS 7.04 / 7.05.


[added 2005-06-22, updated 2006-08-21]

This is an online HTML page, with a documented DEBUG script that patches IBMDOS.COM in DR-DOS 7.04 / 7.05. Other related information also included.

Author: Michal H. Tyc, Poland / BTTR Software, Germany (2003).

Read it online.

More in these pages from BTTR Software.

Still-breathing, major commercial DOSes
Not freeware, but stuff that many people come here searching for.

IBM PC DOS 2000 (PC DOS 7 with Y2K fix) is still available and is worth considering, if you are willing to pay for a 16-bit DOS. The package includes IBM's E editor (originally from OS/2), the REXX language, and other features lacking in MS-DOS. If you already have PC DOS 7, get the free Y2K fix, in any of 14 languages, at IBM's Y2K Fixpak page.

MS-DOS is no longer sold or supported by MS. However, some free updates, supplements, etc. are still available at the MS ftp site, and at a mirror at SunSITE Northern Europe (UK), ftphttp.


Also see the Unix >> DOS page.

4DOS and 4OS2 — Enhanced command processor replacements for DOS and for OS/2.

* * * * *

[added 2004-10-29, updated 2006-03-14]

4DOS and 40S2 are replacements for the and command.cmd processors of DOS and OS/2, respectively. Their great usefulness is that they contain all of the commands of the files they replace, plus many more. A very few examples, from the docs:

4DOS and 40S2 also have powerful batch processing, and many other capabilities. 4DOS works with MS-DOS or PC DOS 3.1 and up, and with DR-DOS / Novell DOS / OpenDOS 3.4 and up. 4DOS can also be the secondary command processor under Win3.1x/9x/Me and OS/2, i.e, what runs in a DOS box. 40S2 works with OS/2 2.1 or later, including Warp, and in a Win3.1x session under OS/2. Both 4DOS and 40S2 were originally releaed as paid shareware, but are now freeware. If you need to know more before you download either one, read the 4DOS Introduction and Installation Guide online.

Publisher: JP Software (2002, 2004).


Available as a Windows installer EXE, which can be unzipped for manual installation. Or, get individual files for manual or custom installation.
Last version from JP Software.
Update by SciTech Software Inc.

4DOS.HLP is an expanded replacement for the help file in 4DOS v7.50.130.
* * * * *
[added 2005-08-03, updated 2006-08-21]
Author: Charles Dye / Freeware, FreeDOS and 4DOS-related stuff.
2006-04-04 release.


Individual files

Expanded HLP


Also see JP Software's related Take Command shells for OS/2 and for Win3.1.

More in these pages from Charles Dye.


These can coexist with DOS/Win9x on the same partition.

BasicLinux (BL3) — Small, low-RAM Linux for older PCs, can boot from DOS partition, diskettes, or CDROM; Internet support.


[added 2000-10-15, updated 2006-08-21]

This Linux distro was designed to run on minimal hardware, yet it includes TCP/IP (Internet) and other networking capabilities (PPP/Ethernet/slattach), an adequate set of network applications (Web browser, mail, ftp, telnet, wget, router/firewall), and other tools (GUI, PCMCIA IDE and CF-card support, Pico text editor, bash, and several Unix tools).

Although many small Linuxes are designed to be booted from floppies, a hard disk boot will obviously be quicker: The "DOS" version of BasicLinux can be unzipped to a hard disk directory and booted immediately from the DOS prompt (about 80 sec. from boot command to login prompt on a 386SX/20 w/8MB RAM, which is fast compared to floppy-only Linux distros). It then runs in a loop file. Requires 3MB RAM (but 8MB to operate without a swap file), and a DOS (including Win 9x in DOS mode).

The "Floppy" version of BasicLinux boots from diskettes and then runs in a 4MB RAM disk, giving it a degree of quickness even on slower CPUs. It provides only about 800K free space, but an additional 4MB RAM disk can be created if you have 16MB+ RAM. You can mount other drives in order to permanently save work from the RAM disk, but you'll need to be comfortable with creating mount points and mounting devices. Requires 12MB RAM minimum, and two 1.44MB diskettes.

Both versions require an 80386+ CPU, and have the option of installing to a dedicated Linux HD partition.

BasicLinux is a fairly safe distribution to use for learning and experimenting; however, it does permit mounting (and modification) of other drives and was not designed for tutorial purposes (e.g., lacks man pages).

Author: Steven Darnold, New Zealand (2006).

2006-01-09: v3.40. Derived from Slackware 4.0 and Linux kernel 2.2.26.

DOS version
Floppy version

Go to the BasicLinux home page for docs and add-on modules via http download, and links to related sites with add-ons and info.

If you know which files you need, go direct to the BasicLinux ftp directory.

ZipSlack — Small Linux distribution, part of Slackware package, still in development.


[added 2001-07-22, updated 2005-12-09]

Not really small, but a reliable package that is worth considering. From the publisher:

ZipSlack is a special edition of Slackware Linux that can be installed onto any FAT (or FAT32) filesystem with about 100 MB of free space. It uses the UMSDOS filesystem and contains most of the programs you will need. This means that you do not need to repartition your hard disk if you already have DOS or Windows installed. ZipSlack installs into a directory on your DOS filesystem. It can also be installed to and booted from a Zip disk.
This distribution is ideal for people who don't have a lot of hard disk space, do not have a fast Internet connection to download the entire distribution, or who want a Linux distribution they can carry around on a Zip disk.

Requires about 107MB allocated disk space, 80386+, 8-16MB RAM.

2005-09-15: Slackware v10.2, with Linux kernels 2.4.31 and 2.6.13.

Go to The Slackware Linux Project for more info. For files. go to Get Slack to find a list of download sites, and then look in a site for a directory something like /linux/distributions/slackware/slackware-10.2/zipslack/.

For purchase of CDs and books, go to the Slackware Store

Pygmy Linux — Small Linux distribution.


[added 1999-09-26, updated 2004-10-29]

From the docs:
... Pygmy is UMSDOS based... co-exists peacefully with DOS/Win95, 98 on the same partition. ...minimal configuration is i486, 8 MB RAM and approximately 25 MB of disk space... internet ready... supports connection via ...modem and ...LAN... allows installation of Slackware, Redhat and Debian packages.

Other features: Based on Slackware 7.1. SVGALIB graphic browser in package. Released under GPL.

Author: Peter Psota, Czech Republic (2002).

2002-10-05: v0.92. Last version – development has ended, author's website is shut down.

Download (13.2MB), from Planet Mirror (Australia) or from Beresta Baikala (Russia).


DOSEMU — Provides DOS system emulation under Linux.

* * * * *

[added 2000-03-06, updated 2005-06-23]

"DOSEMU is a PC Emulator application that allows Linux to run a DOS operating system in a virtual x86 machine. This allows you to run many DOS applications." Requires some native DOS files (e.g.,, io.sys/, msdos.sys/ Compatible with many DOSes, but see the specialized dosemu-freedos at SourceForge, and OpenDOS 7.02-4 on this page.

Capabilities include:

Authors: DOSEMU Team (2004, 2005).


Stable release
Development version, not final, only source is available

Get the latest official releases of DOSEMU and dosemu-freedos at DOSEMU Stable Code.

Get development versions at DOSEMU: Bleeding Edge.

For latest info, go to

LTOOLS (formerly LREAD) — Command line tools read / write Linux ext2 filesystem from DOS/Windows.


[added 2001-08-05, updated 2006-08-21]

All the following functions are included in a single 120K executable (individual functions can be called with included batch files):

Runs on one machine, or over the Internet or any other network. Package includes: A 16-bit DOS version that also runs in a box under Win3.1x/9x/ME; A 32-bit WinNT/2K/XP command line version; A Unix version, which can also be used under Linux to access an unmounted partition; GUI shells for Windows and Unix/Linux; C source code.

Author: Werner Zimmermann, Germany (2006). Suggested by Jon-Egil Korsvold.

2006-02-27: v6.12.

Download (2.1MB).

Go to the LTOOLS Page for lots more info & news.

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