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DOS is an acronym for Disk Operating System but, in common usage, it has come to refer to the disk-based operating systems on personal computers compatible with the IBM PC.

A disk operating system is one that can use a disk storage device, such as a floppy disk, a hard drive, or an optical disk, providing a file system that can organize, read, and write files to the disk. This definition doesn't apply to most modern operating systems, like Apple Macintosh or Microsoft Windows, and is largely applied to older generations of operating systems.

Given that large numbers of older computers are still in use, DOS-type operating systems may still be relevant, however.

Most of the DOS resources referenced in this guide will be historic in nature, and most are no longer supported by their developers, although some are in the public domain or otherwise available.

Although there may be others, one notable exception is FreeDOS, previously known a Free-DOS and PD-DOS. FreeDOS began when Microsoft announced its discontinuance of MS-DOS in 1994, releasing its first version in 1998. Available under the terms of the GNU General Public License, FreeDOS continues to be actively developed.

Another is ROM-DOS, which was introduced in 1989 as an MS-DOS compatible operating system for embedded systems. Additional enhancements have been made to the operating system over the years, and it is still available from its developer, Datalight Tuxera Company, as closed-source software. A single-user version of ROM-DOS is also available for desktop users looking for a replacement DOS.

Other recently active versions of DOS include DR-DOS, RxDOS, REAL/32, and SpartaDOS. Developed in Russia by PhysTechSoft and Paragon Technology Systems, PTS-DOS (PTS/DOS) is a DOS clone still in development for the Russian Ministry of Defense.

Reportedly, on request, some computer manufacturers, including Dell and HP, will sell computers with FreeDOS or DR-DOS installed as original equipment manufacturer (OEM) operating systems.

On most Linux systems, it is possible to run copies of DOS on a Linux-native virtual machine, and there are various emulators available for running DOS on Unix-type systems and Microsoft Windows. DOSBox, for example, is used for legacy gaming on modern operating systems.

Early versions of Microsoft Windows were, in effect, a graphical shell over a DOS system, and users could drop to a DOS command line to run non-graphical DOS programs. Windows 95 was bundled as a standalone operating system that was not dependent on DOS, although the MS-DOS component remained for the sake of compatibility.

However, most computer users today have never used a computer from the DOS command line.

Developed for IBM by Microsoft, PC-DOS was the first widely-installed operating system used in personal computers on Intel 8086 16-bit processors. Microsoft subsequently produced its own nearly identical version called MS-DOS.

Other early computers, the Commodore 64, Atari 800, and Apple II, featured DOS systems, known as CBCM DOS, Atari DOS, and Apple DOS, respectively.

These early operating systems did not multitask; they were able to run only one program at a time. Using a command-line interface, users had to remember the commands that were needed to accomplish computing tasks. The command line was also known as the C-prompt (C:\) or the DOS prompt.

The last retail version of MS-DOS was MS-DOS 6.22. Although MS-DOS was bundled with Windows after that, it no longer required a separate license and was not distributed as a standalone operating system.

The last retail version of PC-DOS was PC-DOS 2000, although IBM later created PC DOS 7.10 for OEM use.

Besides the few versions of DOS that continue to be actively supported, legacy copies of past versions are available from various sources. Some of these may be in the public domain, but the legality of others might be in question.

Whatever the version, topics related to DOS operating systems are appropriate topics for this category.



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