Evilspeak

Evilspeak is a 1981 American horror film directed by Eric Weston and co-written by Weston and Joseph Garofalo. The film stars Clint Howard as an outcast cadet named Stanley Coopersmith, who frequently gets tormented by his mates and advisers at a military academy. Upon finding a book of Black Mass that belonged to the evil medieval Father Lorenzo Esteban, he taps through a computer to conjure Satan and summons spells and demons to get revenge on his harassers.

Synopsis from Wikipedia, CC BY-SA 4.0. Everything below written here.

Poster © the film's rights holders.