Operating Systems
HDOS
Heath Disk Operating System. Four versions were released by Heath: 1.0, 1.5, 1.6, and 2.0 which was the last official version released by Heath. A 3.0 version was released by a third party.
CP/M
Heath released three version of CP/M-80: 2.2.02, 2.2.03, and 2.2.04. Magnolia Microsystems also released 1.4, 2.2, and 3.0 versions of CP/M. CP/M 3.0 was only available with their 128K memory card. DG Electronics offered CP/M Plus and MP/M.
UCSD P-System with Pascal
A version of Pascal from the University of California San Diego, Version II
figForth
I don't have much information on this. I recently received a copy in an acquistion.
CassetteOS
I have never used this, and don't know much about it.