The 18th-century origins of the "universal machine" - when a computer was a human being who did arithmetic.
Interviews:
Paul Ceruzzi (computer historian), Doron Swade (London Science Museum), Konrad Zuse (inventor of the first functional computer and high-level programming language, d.1995), Kay Mauchly Antonelli (human computer in WWII and ENIAC programmer, d.2006), Herman Goldstine (ENIAC developer, d.2004), J. Presper Eckert (co-inventor of ENIAC, d.1995), Maurice Wilkes (inventor of EDSAC), Donald Michie (Codebreaker at Bletchley Park)