12. Woolley, The Bride of Science, 60.

13. Stein, Ada, 16; Woolley, The Bride of Science, 72.

14. Woolley, The Bride of Science, 92.

15. Woolley, The Bride of Science, 94.

16. John Galt, The Life of Lord Byron (Colburn and Bentley, 1830), 316.

17. Ada to Dr. William King, Mar. 9, 1834, Dr. King to Ada, Mar. 15, 1834; Stein, Ada, 42.

18. Ada to Dr. William King, Sept. 1, 1834; Stein, Ada, 46.

19. Woolley, The Bride of Science, 172.

20. Catherine Turney, Byron’s Daughter: A Biography of Elizabeth Medora Leigh (Readers Union, 1975), 160.

21. Velma Huskey and Harry Huskey, “Lady Lovelace and Charles Babbage,” IEEE Annals of the History of Computing, Oct.–Dec. 1980.

22. Ada to Charles Babbage, Nov. 1839.

23. Ada to Charles Babbage, July 30, 1843.

24. Ada to Lady Byron, Jan. 11, 1841.

25. Toole, Ada, the Enchantress of Numbers, 136.

26. Ada to Lady Byron, Feb. 6, 1841; Stein, Ada, 87.

27. Stein, Ada, 38.

28. Harry Wilmot Buxton and Anthony Hyman, Memoir of the Life and Labours of the Late Charles Babbage (ca. 1872; reprinted by Charles Babbage Institute/MIT Press, 1988), 46.

29. Martin Campbell Kelly and William Aspray, Computer: A History of the Information Machine (Westview, 2009), 6.

30. Swade, The Difference Engine, 42; Bernstein, The Analytical Engine, 46 and passim.

31. James Essinger, Jacquard’s Web (Oxford, 2004), 23.

32. Ada to Charles Babbage, Feb. 16, 1840.

33. Ada to Charles Babbage, Jan. 12, 1841.

34. Charles Babbage, Passages from the Life of a Philosopher (Longman Green, 1864), 136.

35. Luigi Menabrea, with notes upon the memoir by the translator, Ada, Countess of Lovelace, “Sketch of the Analytical Engine, Invented by Charles Babbage,” Oct. 1842, http://www.fourmilab.ch/babbage/sketch.html.

36. Babbage, Passages from the Life of a Philosopher, 136; John Füegi and Jo Francis, “Lovelace & Babbage and the Creation of the 1843 ‘Notes,’ ” Annals of the History of Computing, Oct. 2003.

37. All quotes from Menabrea and Lovelace’s notes are from Menabrea, “Sketch of the Analytical Engine.”

38. Charles Babbage to Ada, 1843, in Toole, Ada, the Enchantress of Numbers, 197.

39. Spoken in the film Ada Byron Lovelace: To Dream Tomorrow, directed and produced by John Füegi and Jo Francis (Flare Productions, 2003); also, Füegi and Francis, “Lovelace & Babbage.”

40. Ada to Charles Babbage, July 5, 1843.

41. Ada to Charles Babbage, July 2, 1843.

42. Ada to Charles Babbage, Aug. 6, 1843; Woolley, The Bride of Science, 278; Stein, Ada, 114.

43. Ada to Lady Byron, Aug. 8, 1843.

44. Ada to Charles Babbage, Aug. 14, 1843.

45. Ada to Charles Babbage, Aug. 14, 1843.

46. Ada to Charles Babbage, Aug. 14, 1843.

47. Ada to Lady Lovelace, Aug. 15, 1843.

48. Stein, Ada, 120.

49. Ada to Lady Byron, Aug. 22, 1843.

50. Ada to Robert Noel, Aug. 9, 1843.

CHAPTER TWO: THE COMPUTER

1. Andrew Hodges, Alan Turing : The Enigma (Simon & Schuster, 1983; locations refer to the Kindle “Centenary Edition”), 439. In addition to the sources cited below, this section draws on Hodges’s biography and his website, http://www.turing.org.uk/; the correspondence and documents in the Turing Archive, http://www.turingarchive.org/; David Leavitt, The Man Who Knew Too Much (Atlas Books, 2006); S. Barry Cooper and Jan van Leeuwen, Alan Turing : His Work and Impact (Elsevier, 2013); Sara Turing, Alan M. Turing (Cambridge, 1959; locations refer to the Kindle “Centenary Edition,” with an afterword by John F. Turing, published in 2012); Simon Lavington, editor, Alan Turing and His Contemporaries (BCS, 2012).

2. John Turing in Sara Turing, Alan M. Turing, 146.

3. Hodges, Alan Turing, 590.

4. Sara Turing, Alan M. Turing, 56.

5. Hodges, Alan Turing, 1875.

6. Alan Turing to Sara Turing, Feb. 16, 1930, Turing archive; Sara Turing, Alan M. Turing, 25.

7. Hodges, Alan Turing, 2144.

8. Hodges, Alan Turing, 2972.

9. Alan Turing, “On Computable Numbers,” Proceedings of the London Mathematical Society, read on Nov. 12, 1936.

10. Alan Turing, “On Computable Numbers,” 241.

11. Max Newman to Alonzo Church, May 31, 1936, in Hodges, Alan Turing, 3439; Alan Turing to Sara Turing, May 29, 1936, Turing Archive.

12. Alan Turing to Sara Turing, Feb. 11 and Feb. 22, 1937, Turing Archive; Alonzo Church, “Review of A. M. Turing’s ‘On computable numbers,’ ” Journal of Symbolic Logic, 1937.

13. This Shannon section draws on Jon Gertner, The Idea Factory: Bell Labs and the Great Age of American Innovation (Penguin, 2012; locations refer to the Kindle edition), chapter 7; M. Mitchell Waldrop, “Claude Shannon: Reluctant Father of the Digital Age,” MIT Technology Review, July 2001; Graham Collins, “Claude E. Shannon: Founder of Information Theory,” Scientific American, Oct. 2012; James Gleick, The Information (Pantheon, 2011), chapter 7.

14. Peter Galison, Image and Logic (University of Chicago, 1997), 781.

15. Claude Shannon, “A Symbolic Analysis of Relay and Switching Circuits,” Transactions of the American Institute of Electrical Engineers, Dec. 1938. For a clear explanation, see Daniel Hillis, The Pattern on the Stone (Perseus, 1998), 2–10.

16. Paul Ceruzzi, Reckoners: The Prehistory of the Digital Computer (Greenwood, 1983), 79. See also Computer History Museum, “George Stibitz,” http://www.computerhistory.org/revolution/birth-of-the-computer/4/85.

17. Howard Aiken oral history, conducted by Henry Tropp and I. Bernard Cohen, Smithsonian Institution, Feb. 1973.

18. Howard Aiken, “Proposed Automatic Calculating Machine,” IEEE Spectrum, Aug. 1964; Cassie Ferguson, “Howard Aiken: Makin’ a Computer Wonder,” Harvard Gazette, Apr. 9, 1998.

19. I. Bernard Cohen, Howard Aiken: Portrait of a Computer Pioneer (MIT, 1999), 9.

20. Kurt Beyer, Grace Hopper and the Invention of the Information Age (MIT, 2009), 75.

21. Cohen, Howard Aiken, 115.

22. Cohen, Howard Aiken, 98 and passim.

23. Beyer, Grace Hopper, 80.

24. Ceruzzi, Reckoners, 65.

25. Horst Zuse (son), The Life and Work of Konrad Zuse, http://www.horst-zuse.homepage.t-online.de/Konrad_Zuse_index_english_html/biography.html.

26. Konrad Zuse archive, http://www.zib.de/zuse/home.php/Main/KonradZuse; Ceruzzi, Reckoners, 26.

27. Horst Zuse, The Life and Work of Konrad Zuse, part 4; Ceruzzi, Reckoners, 28.

28. The story of John Atanasoff and the controversy over the credit he deserves has led to some impassioned writings. A historical and legal battle pitted him against the creators of ENIAC, John Mauchly and Presper Eckert. The four main books about Atanasoff are all written by people who sought to take his side in this dispute. Alice Burks, Who Invented the Computer? (Prometheus, 2003; locations refer to the Kindle edition), is partly based on the documents of the legal battle. Alice Burks and Arthur Burks, The First Electronic Computer: The Atanasoff Story (University of Michigan, 1988) is an earlier, more technical book; Arthur Burks was an engineer on the ENIAC team who ended up being critical of Eckert and Mauchly. Clark Mollenhoff, Atanasoff: Forgotten Father of the Computer (Iowa State, 1988) was written by a Pulitzer Prize–winning reporter who was the Washington bureau chief of the Des Moines Register and after hearing of Atanasoff sought to resurrect him from being forgotten by history. Jane Smiley, The Man Who Invented the Computer (Doubleday, 2010) is by the acclaimed novelist who immersed herself in computer history and became an advocate for Atanasoff. For the personal background and involvement of Alice and Arthur Burks, see their “Memoir of the 1940s,” Michigan Quarterly Review, Spring 1997, http://hdl.handle.net/2027/spo.act2080.0036.201. This section also draws on Allan Mackintosh, “Dr. Atanasoff’s Computer,” Scientific American, Aug. 1988; Jean Berry, “Clifford Edward Berry: His Role in Early Computers,” Annals of the History of Computing, July 1986; William Broad, “Who Should Get the Glory for Inventing the Computer?” New York Times, Mar. 22, 1983.