HP's 12c Financial Calculator Turns 30

There aren't many tech products that stick around for 30 years and remain virtually unchanged, but Hewlett-Packard's 12c financial calculator has, and it's still in demand.

Designed for dealmakers, the 12c is engineered to handle complex formulas for calculating loan payments and interest rates, determining bond yields, and constructing depreciation schedules. Since its debut in 1981, the 12c has become a cult classic among finance and business professionals. (Also watch "1980s Solid Gold technology".)

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"Very few dedicated 12c people only have one. I have one in the office and two at home," says Dennis Harms, who was the original project manager for the 12c.

Harms joined HP straight out of Iowa State, where he earned a PhD in numerical analysis. He was put in charge of creating a financial calculator that would be small enough fit in a shirt pocket, precise enough to exceed federal standards, and have a long battery life.

"My first jobs were around working the math behind the buttons on the calculators. One of the big things I did was working on the financial calculations, getting those accurate. I wrote the code for the calculators, too," recalls Harms, who's still with HP today. "I guess I did a good enough job with that, and I was promoted. I got to be the overall project manager for the 12c, which involved the electrical engineers, the mechanical engineers and the software people, which was pretty exciting."

Some of the design decisions that Harms and his team made were a gamble. Most significantly, the calculator uses Reverse Polish Notation (RPN), which is a technique that governs how the user inputs a formula into the calculator. It's simpler and more efficient than standard algebraic notation, Harms says, and it doesn't require bigger, multi-line screens like complex algebraic entry does. But RPN wasn't a method that financial people were used to -- not that it stopped them from embracing the 12c.

Longtime devotees have found a home on Facebook, where they can heap praise on, and post tips related to, the HP 12c.

"My favorite thing about the HP 12c? Loaning the calculator to someone and then having them say ... "uh, your calculator is broken" b/c they don't know RPN! Owned mine for nearly 20 years still use it every day," posted a Facebook user by the name Ravi Nagarajan on the fan page HP 12c Dorks.

"I've had mine for 23 years. Anyone who wants to get it away from me has to practice first with something easier -- like prying Charlton Heston's rifle out of his cold dead hands," posted Steve Finlay.

Origins of the 12c

Development of the 12c started at HP's Advanced Product Division in Cupertino, California, where it wasn't uncommon for HP cofounder Bill Hewlett -- who's known to have had a soft spot for calculators -- to drop by the labs and check out new prototypes. "That was one of his No. 1 interests," Harms says.

The design team wound up moving to HP's plant in Corvallis, Oregon, where the company was building a fabrication operation for a technology called complementary metal oxide semiconductor (CMOS), which would reduce the 12c's power requirements. The calculator also made use of another emerging power-saving innovation: liquid crystal display (LCD) instead of light emitting diodes (LED).

By reducing its power requirements, the 12c could run on replaceable miniature batteries -- which satisfied the fit-in-a-shirt-pocket requirement.

"A lot of technology was coming together right at that point in time," Harms says, citing the low-power CMOS chips and LCD displays. "Those two things were brand new for this calculator line. That made them low power and made it so the batteries last forever in the thing."

Exceeding federal standards was another engineering priority. The HP 12c team designed the calculations to be so precise that the 12c could receive certification by the federal Bureau of Standards (now the National Institute of Standards and Technology). With that certification, the 12c's results were considered legally accurate.

"If two real estate agents sit down, they'll trust the mortgage calculations that they get on the 12c. It's accepted as an industry standard," Harms says. "You could sell a house based on the calculation of the 12c, and that calculation would hold up in a court of law."

Still today, the 12c is one of only two calculators (the other is from Texas Instruments) that are authorized for use during certification exams by CFA Institute, an association of investment professionals.

HP marked the 30-year anniversary with the release of a limited-edition HP 12c, which costs $79.99 and comes with a gift box and a unique production number etched on the back.

Nearly everything else is unchanged. "The inner workings are all the same," Harms says. "They're still running the code I wrote for the thing."

No one would have expected the 12c to last so long, Harms says. "We were in a calculator division of Hewlett-Packard, at that time, and we viewed things as rolling every two years. We would have thought of it as having a two-year life, and expected it would be replaced by the next generation after that."

As for Harms, he left HP's calculator division about a year after the 12c went into production. Throughout his career at HP, he has worked on Unix workstations, Web services, and printers, among other areas.

"Life was good back then," he remembers of his first job at HP. "I sat down next to Bill Hewlett and Dave Packard, who were awesome, awesome guys. They don't make guys like that anymore."

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This story, "HP's 12c Financial Calculator Turns 30" was originally published by Network World.

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