Sorry but what kind of stupid question is that?! Of course he used a spell, tons in fact. Honestly, did you ever even read the book or at least watched a movie or heard about it?
Digitalis is not a spell in Harry Potter.
Harry Potter's favorite spell was Expelliarmus (disarming spell) but he also used Stupefy (stunning spell) a lot.
Stupefy.
Mobiliarabus
Accio
Expelliarmus.
Expecto Patronum
Petrificus totalis
In the fourth book, Harry used the spell, Diffindo, to rip Cedric Diggory.
The spell that Harry Potter used to cause Draco Malfoy to bleed continuously in the bathroom duel scene of "Harry Potter and the Half-Blood Prince" is called "sectumsempra".
Harry Potter attempted to use crucio on Bellatrix Lastrange and later used it on Amycus Carrow.
The spell Expecto Patronum is used for calling your Patronus in Harry Potter.