Variable: c-basic-offset
c-basic-offset is a customizable and buffer-local variable defined in
cc-vars.el.gz.
Documentation
Amount of basic offset used by + and - symbols in c-offsets-alist.
Also used as the indentation step when c-syntactic-indentation is
nil.
This is a style variable. Apart from the valid values described
above, it can be set to the symbol set-from-style. In that case,
it takes its value from the style system (see c-default-style and
c-style-alist) when a CC Mode buffer is initialized. Otherwise,
the value set here overrides the style system (there is a variable
c-old-style-variable-behavior that changes this, though).
Probably introduced at or before Emacs version 19.23.
Source Code
;; Defined in /usr/src/emacs/lisp/progmodes/cc-vars.el.gz
(defcustom-c-stylevar c-basic-offset 4
"Amount of basic offset used by + and - symbols in `c-offsets-alist'.
Also used as the indentation step when `c-syntactic-indentation' is
nil."
:type 'integer
:group 'c)