Signum! Document Toolbox

The Signum! program was a popular word-processor available for the ATARI ST line of home computers and distributed by Application Systems Heidelberg (ASH). While it could be used via the MagicCMac or MagicCPC emulators, it was never ported to newer systems. The file format (.SDO for Signum! and Signum!2) was proprietary or at least unspecified and with the exception of *Papyrus for the ATARI ST and a small amount of other for-profit tools, no other software could read those files. When I started this project, I could not find any software that runs on modern systems and can read those files.

This is especially unfortunate for people (mostly german-speaking) that wrote their thesis in Signum! in the 80s and still have the floppy disks with those files but no ATARI and/or no application anymore. The current solutions are really not worth the effort for some of the less important stuff I’ve found in the stash of floppies I had access to.

Instead, you can use this (work-in-progress) tool, which can read Signum!2 documents and make some of these steps much easier. It’s written in Rust, so it should work across all major platforms (Windows, Linux and OSX).

Table of Contents


  • Load Signum! 1/2 documents (*.SDO)
    • Print all kinds of data from the files to a console, but most importantly
    • Print a list of charset names
    • Print some global formatting options
    • Print a list of pages with additional formatting information
    • Export the document as PDF or HTML or one PNG image per page
      • See examples
      • This requires the E24 font files to be available
      • Font modes (e.g. bold and italic) are not yet supported in all formats
    • Print a list of image names
  • Load Signum! editor charsets (*.E24)
    • Print height and width for each character
    • Print ASCII art for each character bitmap
    • Render a string with the font (use --input "...")
      • currently always “Abcdefghijkl”
    • Generate a visual map of the characters on an ATARI keyboard
      • Examples of those are linked on the chsets page
  • Load Signum! printer charsets (*.P24, *.P09, *.L30)
    • Print height and width for each character
    • Print ASCII art for each character bitmap
  • Load Signum! images (*.IMC, *.I__)
    • Produce a PNG for monochrome images exported from a document


This project is implemented in the Rust programming language. You can either download the compiled executables (recommended) or build the program from source using cargo.

  1. Go to
  2. Download “” where XXX is your operating system
  3. Unzip the archive to sdo-toolbox-XXX
  4. Use/Copy sdo-toolbox/sdo-tool (Linux/OSX) or sdo-toolbox/sdo-tool.exe (Windows)

From Source

  1. Install Rust
  2. Clone this repository (git clone
  3. OR download it from
  4. In the folder that contains Cargo.toml run cargo build --release / cargo.exe build --release
  5. Use/Copy target/release/sdo-tool (Linux/OSX) or target/release/sdo-tool.exe (Windows)

Adding to the path

On Linux and MacOS, you can copy sdo-tool to /usr/local/bin to have it available everywhere. On all operating systems, you can add the sdo-toolbox or release folder to the PATH environment variable (See this guide) for the same result.


At the moment, this program is not released on, so it cannot be installed using cargo install yet.


  1. sdo-tool --format pdf SOMEFILE.SDO to get a PDF file
  2. sdo-tool --format png SOMEFILE.SDO to get a sequence of PNG files
  3. sdo-tool SOMEFILE.SDO to print some text to the console
  4. sdo-tool SOMEFILE.E24 to print all characters in the font to the console
  5. sdo-tool --format png SOMEFILE.IMC to convert an IMC image file to a PNG file
  6. sdo-tool --format pbm SOMEFILE.IMC to convert an IMC image file to a PBM file


$ ls
$ cd sdo-toolbox
$ ./sdo-tool --format pdf ../FILE.SDO
$ open ../FILE.pdf

See this document for examples for the output that this tool produces.


You are free to download, and run this software for any personal and non-commercial reason, at your own risk and without claiming fitness for any particular purpose. If you want to contribute to this project or use it for any kind of distribution or commercial purpose, please contact me.


If you had some reason to use this tool, I’d love to hear your story! Please reach out to me at

Buy Me a Coffee at


  • Lonny Pursell for helping me figure out the image reading based on his zView-compatible codec
  • Oliver Buchmann of Application Systems Heidelberg for helping me set up Signum in an emulator.
  • Thomas Tempelmann for the Megamax-2 Doku as example files (with images!) and a SignumRead (S/MYUTIL/SIGNUMRE.M) Program from his MM2 dev-environment
  • Georg Scheibler for his article and source code for converting 1stWord to Signum
  • The image-rs Developers for the PNG generation library
  • “The 68000’s Instruction Set”, which is excellent but sadly doesn’t include an author
  • Wikipedia editors for confirming that 0 means white for an ATARI ST screen dump
  • The rust compiler + ecosystem people for creating a useful language with really good tooling which made porting 68K assembly to working rust code really smooth