MOS
These are three different operating systems - Czechoslovakia for EC 1021, another system for RPP -16, and finally Russian. MOS also means "Machine Operating System" for Acorn computers.
Czechoslovak system from VÚMS for computer EC 1021 (ZPA 6000/20) from VÚMS. The minimum requirement for RAM was 16 kib.
Mos (RPP-16)
For RPP-16
MOBILNAJA Operationnaja sistema
Russian OS based on V7 Unix, "developed" in Nicevt, USSR, based on UTS.
Runs on EC 1045
Mos successors include Mnos, Demos, Inmos.