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DEMOS was a Soviet operating system derived from BSD Unix.
Commands in BSD are derived from English words. Did DEMOS use these same commands, develop their own commands but retain the Roman alphabet, or create entirely Russian commands in the Cyrillic alphabet? (The first would be the least amount of work, but the last would be the most acceptable to Soviet users.)
Were the commands lower-case (as most BSD commands are) or upper-case?
The commands are more or less the same ones we're used to from BSDs.
Examples cat and ls are clearly visible on this image from the Russian wikipedia page.
But some things, such as the shell, appear to have translated error messages. For example, you can see Команда не найдена, or "Command not found". And this looks like it's running the C shell, exactly as western BSDs do.
DEMOS was an extension of 2.9 BSD, and all the commands, utilities, etc. were kept in place with their original names and everything. The major areas of said extension were:
Add a rudimentary Russian "locale" support for KOI8-R (a modified KOI-8). Almost all of BSD was extremely ASCII-centric, so it took a very significant amount of time and effort to modify the code to make it work with the 8-bit encoding with its non-trivial collation rules. Also, add Russian-language messages everywhere in user space. The message language was controlled by an environ variable (sorry, don't remember which one now - LANG?).
Modify existing or add new drivers for hardware specific to the USSR/Comecon-produced systems, including 8-bit support for terminal multiplexers and terminals.
Produce docs and mans in Russian.
The localization efforts were also ported to more exotic USSR/Comecon architectures based on DEC VAX (with 4.3BSD as the base) and IBM 370 (off of Amdahl UTS). Things like Ingres were also modified to deal with KOI8-R.
print chr$(255)(observing the currency sign ¤ character in place of a $), you'll see Ъ.