MNOS

MNOS (meaning "MobilNaya Operatsionnaya Sistema" (МобильНая Операционная Система, МНОС), or "Portable Operating System") was a Unix-like operating system developed in the Soviet Union. It was derived from Unix Version 6 and consequently heavily modified to incorporate many features of BSD Unix. From 1983 until 1986 it enjoyed significant popularity in the USSR and other Eastern Bloc countries, due to its light weight and better performance than that of Unix Version 7 (and later BSD Unix-based) alternatives.