Leslie Berlin, the historian who oversees Stanford University's Silicon Valley Archives, talks with Recode's Kara Swisher about her new book, "Troublemakers: How a Generation of Silicon Valley Upstarts Invented the Future." The book traces the rise of seven men and women who were pioneers of the tech industry in the 1970s and early 1980s, including ASK Group founder Sandy Kurtzig, Pong designer Al Alcorn and Apple's "adult supervision," Mike Markkula. Berlin says learning about their importance to the history of the tech industry is "like watching the Big Bang." She also talks about the challenges of preserving tech's history when some crucial documents may be stored in obsolete file formats; why the tech boom happened in Silicon Valley, and not some other part of the country; and why the risk of America's immigration laws becoming more restrictive is a great danger to the industry.