RE: [External] : Re: Spaces rather than tabs by a major mode hook

[Drew Adams]

> Suppose I have a file with tabs, would the change
> show the tabs as spaces?
  ^^^^^^^^^^^^^^^^^^^^^^^

> I would rather have the file show as it is.  If there are tabs
> in the file, would (setq-default indent-tabs-mode nil) show them as
> spaces?

What does the doc tell you?

  Indentation can insert tabs if this is non-nil.
                  ^^^^^^

It's about inserting whitespace chars when you
indent text, or when Emacs does that for you.

It's not about what is displayed.  And there's no
changing of what's already there - unless you
edit in such a way that things get reindented.

So no, other than editing, existing TAB chars remain.

To change TAB chars to SPC chars, use `M-x untabify'.