(p. 120) I’d been a slide rule whiz in high school, so when I saw the calculator, it was just amazing. A slide rule was kind of like a ruler– you had to look at it precisely to read the values. The most accurate number you could get was only three digits long, however, and even that result was always questionable. With a calculator, you could punch in precisely the digits you wanted. You didn’t have to line up a slider. You could type in your numbers exactly, hit a button, and get an answer immediately. You could get that number all the way out to ten digits. For example, the real answer might be 3.158723623. An answer like that was much more precise than anything engineers had ever gotten before.
Well, the HP 35 was the first scientific calculator, and It was the first in history that you could actually hold in your hand. It could calculate sines and cosines and tangents, all the trigonometric and exponential/logarithmic functions engineers use to calculate and to do their jobs. This was 1973, and back then cal-(p. 121)culators–especially handheld calculators–were a very, very big deal.
. . .
There was no doubt in my mind that calculators were going to put slide rules out of business. (In fact, two years later you couldn’t even buy a slide rule. It was extinct.) And now all of a sudden I’d gotten a job helping to design the next generation of these scientific calculators. It was like getting to be a part of history.
Wozniak, Steve, and Gina Smith. iWoz: Computer Geek to Cult Icon: How I Invented the Personal Computer, Co-Founded Apple, and Had Fun Doing It. New York: W. W. Norton & Co., 2006.
(Note: ellipsis added.)