USIX

USIX is a Unix-like operating system created by System Six Inc. and INEUM. USIX, complied with the main international standards and agreements (POSIX 1003.1b-1993, SVID), supported real-time mode, had built-in protection against unauthorized access (security level C2), etc. Binary compatible with SVR4 / 386. After System Six closed, OS development ended.
 

Which Operating System is the Best - Vote Now | Top Ten Most Popular OS

"USIX" is at the 30th position in this list.

Votes: 147/3
2%
Popularity
2
67%
Up
1
33%
Down