Til Zilog developed its own operating system, in the form of the comprehensively titled Z80 Operating System with Relocatable Modules and I/O Management (Z80-RIO for short)

Zilog’s Forgotten Operating System: Z80-RIO | Hackaday
https://hackaday.com/2023/10/06/zilogs-forgotten-operating-system-z80-rio/

#retroComputing #z80