Tabs vs. Spaces
===============
Emacs normally uses both tabs and spaces to indent lines. If you
prefer, all indentation can be made from spaces only. To request this,
set `indent-tabs-mode' to `nil'. This is a per-buffer variable, so
altering the variable affects only the current buffer, but there is a
default value which you can change as well. Note:Locals.
There are also commands to convert tabs to spaces or vice versa,
always preserving the columns of all nonblank text. `M-x tabify' scans
the region for sequences of spaces, and converts sequences of at least
three spaces to tabs if that can be done without changing indentation.
`M-x untabify' changes all tabs in the region to appropriate numbers of
spaces.