Ferris uses his PC to alter his absence records on the school's computer. He later also uses it, with a mouse, to complete an "art work".
Year of feature (shown above)
Wait a minute, where is the computer that Mr. Rooney uses to look at Ferris's attendance,or Is that the same computer. That is in Mr. Rooney's office? Plus I love this movie
See my comments at http://imcdb.org/movie.php?id=91042#Comment1276543
Mr. Roony's computer is the real IBM PC meanwhile Ferris' computer is the clone. See the indentation that it is rectangle than where the square IBM badge supposed to be located.