auto-coding-alist

auto-coding-alist is a variable defined in `mule.el'.
Its value is

(("\\.\\(arc\\|zip\\|lzh\\|lha\\|zoo\\|[jew]ar\\|xpi\\|rar\\|7z\\|ARC\\|ZIP\\|LZH\\|LHA\\|ZOO\\|[JEW]AR\\|XPI\\|RAR\\|7Z\\)\\'" . no-conversion-multibyte)
 ("\\.\\(exe\\|EXE\\)\\'" . no-conversion)
 ("\\.\\(sx[dmicw]\\|odt\\|tar\\|t[bg]z\\)\\'" . no-conversion)
 ("\\.\\(gz\\|Z\\|bz\\|bz2\\|xz\\|gpg\\)\\'" . no-conversion)
 ("\\.\\(jpe?g\\|png\\|gif\\|tiff?\\|p[bpgn]m\\)\\'" . no-conversion)
 ("\\.pdf\\'" . no-conversion)
 ("/#[^/]+#\\'" . utf-8-emacs-unix))

Documentation:
Alist of filename patterns vs corresponding coding systems.
Each element looks like (REGEXP . CODING-SYSTEM).
A file whose name matches REGEXP is decoded by CODING-SYSTEM on reading.

The settings in this alist take priority over `coding:' tags
in the file (see the function `set-auto-coding')
and the contents of `file-coding-system-alist'.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.1 of Emacs.