Why are some files empty?

I was browsing through the source code and came to the stdlib directory. And I saw that some files had no content, like [io.cyrus](https://github.com/cyrus-lang/Cyrus/blob/initial-compiler/stdlib/io.cyrus), [mem.cyrus](https://github.com/cyrus-lang/Cyrus/blob/initial-compiler/stdlib/mem.cyrus). Why? Is there a specific reason?