Unset ignorecase in vim?

:set noic, or :set noignorecase

Really intuitive, right? :)

You can also toggle the setting with :set ic! and query its value with :set ic?

Pay attention to 'smartcase' option. It overrides the 'ignorecase' option if the search pattern contains upper case characters.

i.e. having 'ignorecase' and 'smartcase' on /foo will find foo, Foo and FOO, but /Foo will find only Foo, not foo.

You can also tell Vim that you want to search case-sensitive despite of 'ignorecase' setting by using \C somewhere in the search pattern. By using \c in the search pattern you tell Vim to ignore case while searching, despite of 'ignorecase' setting.