atrforge Documentation

DOS FORMATS

DOS Formats Support

The Atari 8-bit world had many different DOS formats. Some were official, some were third-party, and some were... creative. atrforge tools support reading from many of them, and creating images in SpartaDOS/BW-DOS format. Let's talk about what works and what doesn't.

Creation Support

SpartaDOS / BW-DOS

Full read/write support. This is what atrforge creates, and it's what most of the tools work with.

Features:

  • Up to 16MB images
  • Subdirectories
  • File attributes (protected, hidden, archived)
  • Long filenames (up to 11 characters, 8.3 format)
  • Efficient filesystem structure

Why this format? It's widely supported, efficient, and has all the features you need. It's the format of choice for most modern Atari software.

Read-Only Support

These formats can be read and extracted, but not created or modified by atrforge tools:

Atari DOS 1.0

The original Atari DOS. Single density only (90k disks).

Limitations:

  • Single density only
  • No subdirectories
  • Simple file structure
  • 64 files maximum per disk

When you'll see it: Old software, original Atari disks from the early 1980s.

Atari DOS 2.0

The improved Atari DOS. Supports both single and double density.

Features:

  • Single and double density
  • Better file management
  • Still no subdirectories
  • 64 files maximum per disk

When you'll see it: Most commercial Atari software from the mid-1980s.

Atari DOS 2.5

Enhanced density support. The last official Atari DOS.

Features:

  • Single, double, and enhanced density (130k)
  • Improved file handling
  • Still no subdirectories
  • 64 files maximum per disk

When you'll see it: Later Atari software, enhanced density disks.

MyDOS

A popular third-party DOS that supports large disks.

Features:

  • Up to 16MB images
  • Subdirectories
  • Better file management than Atari DOS
  • More files per disk

When you'll see it: Power users, large disk images, modern Atari software.

LiteDOS 2.x / LiteDOS-SE

Lightweight DOS variants. Simple but functional.

Features:

  • Basic file management
  • Subdirectory support (in some versions)
  • Smaller footprint than full DOS

When you'll see it: Minimal setups, boot disks, specialized applications.

Special Formats

These aren't really DOS formats, but they're stored in ATR files:

BAS2BOOT Images

A bootable image format that contains a BASIC program.

What it is: An ATR image with a BASIC program that boots automatically.

What atrforge does: Extracts the BASIC file from the image.

When you'll see it: Bootable BASIC programs, educational software.

Howfen DOS Images

A specialized boot image format.

What it is: A bootable image with a specific structure.

What atrforge does: Extracts the raw BOOT image.

When you'll see it: Specialized boot disks, custom boot loaders.

K-file Boot Images

Boot images that contain XEX files.

What it is: A bootable image with an XEX file inside.

What atrforge does: Extracts the XEX file.

When you'll see it: Game boot disks, executable boot images.

Format Detection

When you use lsatr on an ATR image, it tries to detect the format automatically:

  1. SpartaDOS/BW-DOS - Checks for SpartaDOS filesystem structure
  2. Howfen DOS - Checks for Howfen DOS signature
  3. Atari DOS - Checks VTOC and directory structure
  4. MyDOS - Checks MyDOS signature and structure
  5. LiteDOS - Checks LiteDOS signature
  6. Special formats - Checks for BAS2BOOT, K-file, etc.

It tries each format in order until it finds one that works. If none work, it reports that the format isn't supported.

Compatibility Notes

What Works

  • Reading: All listed formats can be read and files extracted
  • Creating: Only SpartaDOS/BW-DOS images can be created
  • Modifying: Only SpartaDOS/BW-DOS images can be modified (with -a or atrcp)

What Doesn't Work

  • Creating other formats: You can't create Atari DOS, MyDOS, or other format images
  • Converting formats: You can't convert between DOS formats (only ATR format conversion)
  • Some features: Not all features work with all formats (attributes, subdirectories, etc.)

Limitations by Format

FormatReadWriteSubdirsAttributesMax Size
SpartaDOS/BW-DOS✓✓✓✓16MB
Atari DOS 1✓✗✗✗90k
Atari DOS 2.0✓✗✗✗180k
Atari DOS 2.5✓✗✗✗130k
MyDOS✓✗✓✗16MB
LiteDOS✓✗Partial✗Varies

Why Only SpartaDOS/BW-DOS for Creation?

Good question. Here's why:

  1. It's the most capable - Supports everything you need
  2. It's widely compatible - Works with most Atari systems and emulators
  3. It's what we know - The tools were designed around this format
  4. It's efficient - Good filesystem structure and performance

If you need other formats, you can:

  • Create in SpartaDOS/BW-DOS, then convert on the Atari
  • Use other tools that support those formats
  • Extract from existing images and work with the files

Tips for Working with Different Formats

  1. Check format first - Use lsatr to see what format an image uses
  2. Extract and recreate - If you need to modify a non-SpartaDOS image, extract files and create a new SpartaDOS image
  3. Preserve originals - Keep original images when extracting, in case you need the original format
  4. Check compatibility - Make sure your target system supports the format you're creating

See Also

  • atrforge - Creating SpartaDOS/BW-DOS images
  • lsatr - Reading and extracting from various formats
  • ATR Format - Technical details about ATR file format

For the complete tool list, see the main documentation index.