Encoding. Tortured with Russian symbols. Can you help?

Question

Character encoding

Win 10 LTSC. Installed gVim. I'm learning the C language, but then I decided to write in Russian letters and I can't figure it out.

The command line itself has Russian letters.

Microsoft Windows [Version 10.0]
(c) 2018 Microsoft Corporation. All rights reserved.

Russian letters are written in the editor, the file is saved. But in the compilation I get this:
╨v╤G╤V ╤P

Can you please describe step by step what and how to do. Thanks to