A Z80-family operating system.
Wozmon (written by Steve Wozniak in 1976) for the Z80 and Z80-family of peripherals is used as entrypoint to the operating system. It is a modified version of ZMon.
I use Vasm oldstyle to assemble this project.
$ vasmZ80_oldstyle -Fbin -dotdir zos.sI use Minipro for writing a.out to an EEPROM.
$ minipro -p W27C020 -s -w a.out