Maybe a dumb question, but what kind of programming languages and operating systems were used at that time in the Soviet Union? Were c and unix a thing there as well?
SM-1800 was Intel based, not PDP-11 based. 1800 was based on Russian variant of 8080, and 1810 had both 8080 and 8086 as I remember. https://ru-m-wikipedia-org.translate.goog/wiki/%D0%A1%D0%9C_... will give overview of the SM series.
Regarding OS - PDP-based were initially on RSX, later on Soviet variants of unix. Intel based had either custom OS for 8080, or ms-dos like for x86 - Wikipedia article covers it well.
Same as everywhere: C/C++, Pascal, Fortran, BASIC. There were some exotics, like translated versions of the languages (similar to Chinese version of Python these days), but they were rare. My dad had a translated C manual printed on a matrix printer, A3-size, album orientation, with hand-made hard cover. I saw a book (made in state press) on IBM 360.
But these were 1980s. A teacher told me they were using punch cards in the '70s.