Didn’t Drum The Subject Home

(My nephew comes back home from his computer science exam and gives his mother the question paper.)

Mother: *reading from the question paper* “I’m a storage device circular in shape. What am I?”

Nephew: “Drum. To store water.”

Mother: “How do you get a drum into a computer?”

Nephew: *in a voice that indicates the dawn of a revelation* “I totally forgot it was a computer science exam.”