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Early Computers Intern: I ’ m studying early computers in my Intro to Computing course. Technology is so much more advanced now! Engineer: Yes, we ’ ve come a long way since the days of vacuum tubes. Intern: Definitely. We watched a ( 1 ) program about those. It said that tubes failed practically every day. Can you imagine that? Engineer: I ’ m sure it was really frustrating. Intern: Solid-state ( 2 ) is so much better. Hard drives hold so much more information. And they ’ re way more reliable. Engineer: Well actually, a hard drive isn ’ t solid-state. It ’ s electromechanical. Intern: Really? I thought they were made from solid parts. Engineer: Technically, that ' s true. But ( 3 ) with moving parts aren ’ t really solid-state. Intern: Oh, okay. I thought solid-state just meant it didn ’ t have ( 4 ) tubes. Engineer: No, solid-state electronics are made out of semiconductors. Intern: That means they have both electrons and (5) holes, right?