Atari DOS, (often just known as DOS), was the disk operating system used with the Atari 8-bit family of computers.

The standard Atari operating system that was part of the ROM only contained very low level routines for accessing disk-drives. So an extra layer was added to assist in organising higher level disk-access (such as file systems). This was called DOS.

As DOS was not part of the ROM, it was booted from a floppy disk.

Versions of Atari DOS

There were several versions of Atari DOS available.

Atari DOSses

DOS 1.0

The first version of DOS from Atari. Came with the 810 disk-drives.

DOS 2.0

The second (and probably the most widely used) version of DOS from Atari. Came with the 810 disk-drives and some early 1050 disk-drives. This is considered to be the lowest common denominator for ATARI DOSses, as any Atari-compatible disk-drive and read a disk formatted with DOS 2.0

DOS 3.0

A new version of DOS that came bundled with the new 1050 disk-drives from Atari. This made use of the new Enhanced Density capability (referred to by Atari as Dual Density) offered by the 1050. Unfortunately, this was completely incompatible with previous DOS versions (but there was a utility to read DOS 2 disks). Thanks to the way it organised data into blocks instead of sectors, it wasted a lot of space if there were many small files. This was not one of the popular DOSses. Once Atari released DOS 2.5, DOS 3 fell to obscurity.

DOS 2.5

After listening to complaints by their customers, Atari Released an improved version of their previous DOS. This allowed the use of Enhanced Density disks, and there was a utility to read DOS 3 disks. DOS 2.5 was shipped with 1050 disk drives and some early XF551 disk-drives.

DOS XE

When the Atari XF551 drive came out, not only was it Atari's first drive that could read Double Density disks, it was also double sided. So support was added in the DOS for Double Density and Double Sided disks. This DOS was also compatible with DOS 2.5

Also new in this DOS was date-stamping of files.

Third-party DOSses

Many of these DOSses were released by manufacturers of third party drives, anyone who made drive-modifications, or anyone who was dis-satisfied with the available DOSses. Often, these DOSses could read disks in higher densities, and could set the drive to read disks faster (using Warp Speed or Ultra-Speed techniques). Most of these DOSses (except Sparta DOS) were DOS 2.0 compatible.

Smart DOS

Compatible with DOS 2.0 - Allowed the use of Enhanced Density and Double Density floppies.

OSS DOS

A DOS produced by Optimized Systems Software . Compatible with DOS 2.0 - Allowed the use of Double Density floppies. Disks formatted in OSS DOS on some third-party drives could also be read faster. Unlike most ATARI DOSses, this used a command line instead of a menu.

Super DOS

This DOS could read SS/ED/DD/DS disks, and made use of all known methods of speeding up disk-reads supported by the various 3rd party drive-manufacturers.

Top DOS

Based on Atari DOS but with more features.

MyDOS

This DOS adds the ability to use sub-directories, and supports hard-drives.

SpartaDOS

This DOS used a command-line interface. Was not compatible with DOS 2.0, but could read DOS 2.0 disks.

BW-DOS

A Sparta-DOS compatible DOS released many years later.

External links

• What are Atari DOS 1, DOS 2.0S, DOS 3, DOS 2.5, and DOS XE? — From the Atari 8-bit FAQ.
• Atari DOS Reference Manual — Reference manual for DOS 3.
• Inside Atari DOS