default-buffer-file-coding-system

default-buffer-file-coding-system is a variable defined in `C source code'.
Its value is

utf-8-unix

• This variable is obsolete since 23.2;
  use `buffer-file-coding-system' instead.

Documentation:
Default value of `buffer-file-coding-system' for buffers not overriding it.
This is the same as (default-value 'buffer-file-coding-system).