Business Impact

Computing Before Silicon

The differential analyzer showed the world machines could compute.

Historians disagree about how to categorize the machine pictured above. Was it the first computer? A mammoth mechanical calculator? But there is no question that the differential analyzer-shown with its inventor, MIT’s Vannevar Bush-was a crucial player in the history of computing.

Bush designed the device to solve differential equations in an attempt to model the rapidly expanding power systems of the 1920s. When completed in 1931, the analyzer used electric motors to drive shafts and gears that represented each term in a complicated equation.

The differential analyzer showed the world that machines were suited not just for physical labor, but for mental labor as well. It alerted researchers and funders to the profound possibilities of computers. Bush became director of the Office of Scientific Research and Development-precursor to the National Science Foundation. But though his vision helped shape the government’s attitude toward science, Bush had a blind spot when it came to the digital revolution: He refused to fund early projects in digital computing, including the University of Pennsylvania’s landmark ENIAC. And though the differential analyzer was, in Bush’s words, “the first of the great family of modern analytical machines to appear-the computers, in ordinary parlance,” today’s PCs aren’t direct descendants of his contraption. Bush’s was an analog machine; it represented numbers with physical qualities that vary continuously-distance, rotation and so forth-rather than with the discrete 1s and 0s of digital devices.

This story is part of our May/June 2000 Issue
See the rest of the issue
Subscribe

Still, the differential analyzer was a critical, if inadvertent, midwife to the birth of digital technology. While laboring over the machine and observing the logic of its action, one of Bush’s students-a mathematician named Claude Shannon -began thinking of new ways to build circuits. Shannon realized that the “true” and “false” of Boolean algebra could be represented by the “on” and “off” positions of an electrical switch-in other words, he came up with the idea of a bit.

Shannon’s work with the differential analyzer led to a thesis published in 1938 that has been called “one of the most important master’s theses ever written.” In it, Shannon laid out the logic upon which all digital circuits are now based.

Become an MIT Technology Review Insider for in-depth analysis and unparalleled perspective.
Subscribe today

Uh oh–you've read all five of your free articles for this month.

Insider Premium

$179.95/yr US PRICE

More from Business Impact

How technology advances are changing the economy and providing new opportunities in many industries.

Want more award-winning journalism? Subscribe to Insider Premium.

  • Insider Premium {! insider.prices.premium !}*

    {! insider.display.menuOptionsLabel !}

    Our award winning magazine, unlimited access to our story archive, special discounts to MIT Technology Review Events, and exclusive content.

    See details+

    What's Included

    Bimonthly home delivery and unlimited 24/7 access to MIT Technology Review’s website.

    The Download. Our daily newsletter of what's important in technology and innovation.

    Access to the Magazine archive. Over 24,000 articles going back to 1899 at your fingertips.

    Special Discounts to select partner offerings

    Discount to MIT Technology Review events

    Ad-free web experience

    First Look. Exclusive early access to stories.

    Insider Conversations. Join in and ask questions as our editors talk to innovators from around the world.

You've read of free articles this month.