The Calculator that Never Dies

Thirty years ago, a former Iowa farm boy led a team that produced probably the most successful product of the time, one that, thirty years later, it is still selling in its original form and is used by over 100 million people worldwide.

I’m not talking about that famous IBM PC that was born the same year, now only a museum piece. I’m talking about a pocket sized device that revolutionized the way financial calculations were made--the HP 12c Financial Calculator.

That former farmer boy was Dennis Harms, who joined HP fresh from Iowa State with a Ph.D. in numerical analysis, and was put in charge of creating a financial calculator that would fit in a shirt pocket, be reliable and have a long battery life.

The HP 12c is a consumer electronics product that today is still sold with the original model name, and has not changed its design in the last thirty years. A newer version, the HP 12c Platinum, was introduced a few years ago, but most HP 12c users rejected it: it was not built the same way and had a few changes the HP 12c users didn’t like!

What happens when companies push too far with product development that favors the new over the old? The results aren’t always positive, I am afraid. They violate one of those universal laws of marketing by creating products that their customers don’t want.

I fell in love with the 12c back in the 80’s when I returned to Spain. I was already a fan of HP calculators; those were the equivalent of pocket computers for us in engineering school. The 12c was similar, but different. If you have not used an HP calculator in those years you don’t know what you missed. The keys were solid, they had a unique feedback, and a mechanical click you could feel, making sure you really pressed the key.


They were expensive, oh yes, the 12c retailed for $150 of 1981. Today it sells for $61 at Amazon and the HP web store, around 20% of the original price in today’s dollars.

The designers packed a suite of financial functions and made the 12c so accurate that could win the approval of the National Bureau of Standards, making it suitable for the banking industry. The algorithms used to perform calculations such as bond interest and partial payments on home mortgages were critical if the calculator was to be trusted by the financial world and meet the U.S. standards.

There are some people that trust no other calculator in the market to do the job. Dale Kern, a Real Estate broker in Oregon has three of them. One in his briefcase, one on his desk, and another one for backup. He heard the rumor a few years ago that they will stop producing them, so he went out and bought another one, just in case. “Stop making the HP 12c? Not likely” he says.

One of main reasons for the HP 12c’s success is the way it was designed at that time. It is no secret that Hewlett was a big fan of calculators. Harms believes that the 12c’s success was the result of uncompromising quality and an enormous amount of work and forethought plus a “certain amount of luck”, he acknowledges.

The designers wanted to use RPN logic in the 12c, because it would make it easier to operate and program, and would save memory (counted in single bytes at that time), but the marketing people did not want a product that was working in a different way of the desktop calculating machines. “We decided to force it,” Harms says. It never became an issue with the customers. People were so glad to get the 12c and the power that it gave them that they taught themselves to use RPN, he says. This is one of the main reasons I really like the 12c, RPN is the way all calculators should operate.

And battery life; the original design of the 12c had two button cell batteries, but the team could not live with the worst case scenario of a battery life of three weeks, so they decided to add a third one. But in order to do so they needed to place them vertically, and in the process the back of the calculator was thicker than the front, so it had an angle that made it easier to read. People thought it was designed that way on purpose. I never changed the batteries of my 12c, but I was not a heavy user. HP used silver oxide batteries in the 1980s, before they were restricted to US military use only – so you could expect 10 years or more life out of the original models. Many users reported using them for several years without the need to change batteries.

The HP 12c is so popular they are emulators for all major Smartphone OS’s, including an official app from HP for the iPhone and iPad, and another for Android phones. “it can’t be only nostalgia” says Paul Furber, a columnist for ItWeb, “because even people who weren't born when the 12C came out are devoted users”, he adds.
If you have never used an HP 12c give it a try, or download an app for the iPhone or your Android phone. And if you never used RPN you don’t know what you are missing.

By the way, the official user manual of the HP 12c is available on the HP web site here. It was written in 1981. It is an excellent book on basic financial math, worth reading as well.


Article first published as The Calculator that Never Dies on Technorati.

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