Indent Tabs Mode

By default, Emacs inserts tabs in place of multiple spaces when it formats a region. (For example, you might indent many lines of text all at once with the indent-region command.) Tabs look fine on a terminal or with ordinary printing, but they produce badly indented output when you use TeX or Texinfo since TeX ignores tabs.

The following turns off Indent Tabs mode:

;;; Prevent Extraneous Tabs
(setq-default indent-tabs-mode nil)

Note that this line uses setq-default rather than the setq that we have seen before; setq-default sets values only in buffers that do not have their own local values for the variable.