 SpartaDOS X 4.0 was originally developed by Michael Gustafson in
1987-89, and shipped on 64k ROM cartridges by
ICD, Inc.
up to version 4.21.The cartridge contained an additional cartridge slot on itself, so that it was possible to plug-in another cartridge, such as ICD's R-Time 8 battery-backed clock, a language cartridge (Action!, MAC/65 etc.