@wolf480pl @amonakov I think that depends on what kind of language you want to make.
Like C for example barely abstracts the operating system, and that's one of the big reasons why you can use it everywhere but also why the programs typically aren't as portable as with a language which abstracts the OS.

And there can be other standards in place for common APIs outside of the stdlib (POSIX for Unixes, DOM APIs for ECMAScript/JavaScript, OpenGL and Vulkan for graphics, …).