FA C U LT Y H I G H L I G H T
Bit Players
F O U R T H AY E R FA C U LT Y M E M B E R S C O N S T R U C T A B I N A R Y C A L C U L AT O R T O S H OWC A S E H OW A C O M P U T E R R E A L LY WO R K S
By Craig Salters ’86
The bad news: it took four of Thayer’s best and brightest faculty members over 100 hours of work to successfully add 255 to 255. The good news: they did so to better understand the inner workings of a computer and pass that knowledge on to their students. “This was built, intentionally, as a teaching tool,” said Upper School Math Faculty Tom Chiari P ’22, ’22 as he explained the finer points of the TA-255, the binary calculator he collectively constructed with Upper School Computer Science and Science Faculty Christopher Allen, Kevin Cedrone P ’22, and Don Donovan P ’10, ’13. The “TA” reference should be obvious; the number “255” refers to the largest input number the device can handle. Put another way: the calculator can add from 0 + 0 up to 255 + 255, so the range of its potential answers is between 0 and (Spoiler Alert) 510.
“All a computer is doing is a lot of very simple
Chiari described the computer’s heart and soul
calculations very quickly,” said Cedrone, point-
this way: “You’re basically adding two binary
ing to a row of computers in the Academy’s
digits together: 0 + 0, 1 + 0, 0 + 1, or 1 + 1.”
computer lab which operate to the tune of three
Chiari described the project as “a journey”
to four billion computations per second. “We’re
which began when he wanted to better under-
trying to drill down to how a computer actually
stand how “binary logic gates” work. Cedrone
does what it does.”
gave Chiari a photocopied chapter of Code: The Hidden Language of Computer Hardware
The wood-framed TA-255 is roughly the size
and Software by Charles Petzold.This book is
of a breadbox. It contains eight “switches” for
given annually as a computer science prize at
the first inputted number and another eight
Commencement.
switches for the second inputted number. There are eight circuit boards, each made up of relays,
“I read the first part of the book once and the
diodes, and lots of wire, but at the heart of the
second part of the book seven times,” said
TA-255 — at the heart of all computers, really
Cedrone.
— is the binary digit, or “bit” for short. And that simply means 0 or 1.
Long story short: Chiari read the chapter from the book, which helped him to fully understand
“Everything a computer does, from adding two
the logic gate diagram.
numbers to storing your favorite selfie, it does with 0s and 1s,” said Allen. “However, when a computer adds 1 + 1, it doesn’t get 2. Instead, the computer does its work in base 2 and gets 10 as the answer.”
Scan the QR code to see a video demonstration of the TA-255 by Tom Chiari
or visit bit.ly/TA-255
Scan the QR code to watch a video of the TA-255 in action and explained by Tom Chiari 16
Thayer Magazine /// Winter / Spring 2019
