# How Is a Quarterback Like Your Laptop? [Excerpt]

The famous San Francisco 49ers coach Bill Walsh figured out how to make football digital

Editor’s note: From Newton’s Football: The Science Behind America’s Game by Allen St. John and Ainissa G. Ramirez Ph.D. Copyright (c) 2013 by Allen St. John and Ainissa G. Ramirez, Ph.D. Reprinted by arrangement with Random House. All rights reserved.

How is a quarterback’s progression like a spreadsheet on your laptop? They’re both powered by binary language. That’s when a complex problem is reduced to a series of simpler questions that offer only two mutually exclusive options. The Quarterback’s Cosmic Checklist—Yes, the safety is blitzing / No, he is not—runs on this simple but very powerful mode of communication.  So does Morse code. So does everything from a smartphone to a nuclear power plant.

In a computer, the two positions of a simple switch—voltage on and voltage off—become a language that can be understood by a computer’s central processing unit. A series of 1s and 0s in a specific order can be used to represent an alphabet, and more important, they can encode all the rules of math in a very compact algorithm. A simple calculation written in decimals might take as many as 100 rules, while the same calculation in binary can be accomplished in only four.

This brand of mathematics is called Boolean algebra, named after George Boole, a nineteenth-century mathematician and philosopher. His use of 1s and 0s and true-or-false statements is the computer equivalent of the yes-or-no statements found in human languages—or Bill Walsh’s quarterback reads.

For more than half a century after Boole’s death, Boolean algebra was mostly of interest to mathematicians, but in 1937 a clever graduate student from MIT, Claude Shannon, recognized that Boolean logic could allow electronic circuits to “speak” with each other. Simple switches communicated with each other by turning on or off, which can be read as a one or a zero. If the switches are arranged along Boolean logic, then the two simple digits can represent large numbers and complex mathematical operations.  In 1937, Shannon laid the foundation for the circuits that Bell Labs used to route telephone calls to their proper destinations.

These yes-or-no propositions also became the foundation of computer programming. A hard drive uses the north and south poles of a magnet to store digital data. The spinning disc is covered with a thin magnetic film and a read-write head hovering above it which “senses” the direction of the magnetic regions (or bits) on the disc. CD, DVD, and Blu-ray players work in essentially the same way, except that small pits of long and short lengths are read by a laser replacing the magnetic head of the hard drive. Shannon’s binary language provided the seed for a new field called information theory, which now explains everything from cryptography to gambling probabilities.

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In his West Coast offense, Walsh got his quarterbacks to see the world in black and white. He took a complex situation and broke it down into simple yes-or-no decisions of the kind that microprocessors can make with lightning speed. He then built these true-or-false tests into the kind of if-then decision trees that are the center of computer programming languages. In short, Bill Walsh made football digital.

“Bill’s offense was a progression offense where you had a first, second, third, and fourth receiver,” Ken Anderson, who played quarterback for the Bengals. Anderson would know: he was drafted by Walsh. “You have a primary receiver that you’re going to go to first. A secondary, if that guy’s covered. And there’s a third receiver that’s an alternative. And usually some kind of flare control to a running back or tight end that’s a fourth in your progression. The whole theory is the defense can’t take everything away. If you can get through the progression quickly enough before the pass rush gets to you, you can find someone that’s open for a completion.”

Walsh’s progression is not only about compressing a series of decisions into the shortest amount of time. It’s about linking those decisions to the actions of the defense. Each step of the progression led to a yes-or-no decision, choreographed to each step of a quarterback’s drop, depending on the coverage he saw in the defense.

There’s an elegant simplicity to Walsh’s offense, so much so that it can actually be shoehorned into a rhyme. Sam Wyche, a quarterback who was there during the early days of the West Coast offense, turned his progression into a little couplet: “1–2–3 Guarantee.”