The Museum of HP Calculators

HP Forum Archive 18

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HP-35 and CORDIC-articles at Dr. Dobb's
Message #1 Posted by Karl-Ludwig Butte on 18 Nov 2007, 5:32 a.m.


in the latest "Dr. Dobb's Report" e-mail-newsletter Jonathan Ericson mentioned the CORDIC algorithm implemented in the HP-35 and linked to two CORDIC articles from Dr. Dobb's Journal. Alas, I couldn't find the text of the newsletter at So here is the relevant part: "Unless you're doing something like reverse engineering an HP-35 calculator, you probably don't run across CORDIC algorithms every day. Which makes me wonder why I'm so lucky. Short for "COordinate Rotation DIgital Computer," the CORDIC algorithm was developed in 1956 by Jack Volder when developing navigation systems for B-58 bombers. In the 1970s, the algorithm found its way into calculators like the HP-35. I didn't stumble across CORDIC algorithms until 1990, when Pitts Jarvis wrote Implementing CORDIC Algorithms, which was followed by Michael Pashea's Microcontrollers & CORDIC Methods in 2000. Ever since then, CORDIC algorithms and I have had a hit-or-miss relationship. Until recently. Then a day or two ago, I was reading an interesting article by Anthony Williams entitled "Optimizing Math-Intensive Applications with Fixed-Point Arithmetic," which explains how Anthony optimized C code so that helicopters could fly faster and safer. And wouldn't you know it, CORDIC popped up: "The single biggest gain was achieved by optimizing the trigonometric and exponential functions. For the trig functions, the CORDIC method was used."

You can find the first mentioned article "Implementing CORDIC algorithms" at and the second article "Microcontrollers & CORDIC Methods" at

Have fun

Amazing! Priceless readings. Thanks! (N.T.)
Message #2 Posted by Vieira, Luiz C. (Brazil) on 18 Nov 2007, 12:20 p.m.,
in response to message #1 by Karl-Ludwig Butte

Re: HP-35 and CORDIC-articles at Dr. Dobb's
Message #3 Posted by Karl Schneider on 25 Nov 2007, 4:11 a.m.,
in response to message #1 by Karl-Ludwig Butte

Hi, Karl-Ludwig --

I'll second Luiz' "thanks". I'll read the articles and bookmark the post after it goes to Archives. I've read other journal articles as well as assistance provided by at least one other member of this Forum, but CORDIC still doesn't make intuitive sense to me the way Taylor series do.

-- KS

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