(emacs)Search Case

Searching and Case
==================

   Incremental searches in Emacs normally ignore the case of the text
they are searching through, if you specify the text in lower case.
Thus, if you specify searching for `foo', then `Foo' and `foo' are also
considered a match.  Regexps, and in particular character sets, are
included: `[ab]' would match `a' or `A' or `b' or `B'.

   An upper-case letter in the incremental search string makes the
search case-sensitive.  Thus, searching for `Foo' does not find `foo'
or `FOO'.  This applies to regular expression search as well as to
string search.  The effect ceases if you delete the upper-case letter
from the search string.

   If you set the variable `case-fold-search' to `nil', then all
letters must match exactly, including case.  This is a per-buffer
variable; altering the variable affects only the current buffer, but
there is a default value which you can change as well.  Note: Locals.
This variable applies to nonincremental searches also, including those
performed by the replace commands (Note: Replace.).