;;tab and space
;;when true,emacs use mixture of tab and space to archieve
(setq-default indent-tabs-mode nil)
;;control length used to offset.
(setq-default c-basic-offset 4)
;;control how emacs explain TAB
(setq-default tab-width 4)
;;setup line number
(global-linum-mode t)
原文：http://www.cnblogs.com/fangying7/p/4619904.html