The two “computers” that refuse to die

These devices, designed decades ago, don’t connect to the internet. The 80-year old E-6B flight computer and the 40-year old HP-12c calculator are still being sold in their original form and continue in use by millions of people worldwide.

Pablo Valerio
5 min readMay 19, 2021
Spock using a E-6B computer during the episode “The Naked Time”

What happens when companies push too far with product development that favors the new over the old? Nothing positive: they violate one of those universal laws of marketing by creating products that their customers don’t want.

The E-6B Flight Computer

Many years ago, I had the opportunity to realize one of my lifetime dreams: Learn to fly.

At the time, I was doing a project in Tampa Bay, FL., and I enrolled in the flight school at Albert Whitted Airport (KSPG) in Saint Petersburg.

Until that moment, I thought the word computer only applied to electronic devices that did calculations. Being an engineer, I had used “computers” most of my adult life. Still, my flight instructor introduced me to a curious device: a sort of slide rule made out of cardboard with a round clock-like bezel full of numbers. He called it the E-6B Flight Computer.

So my shopping list to start flight training consisted of the latest FAA rules, a decent aviation headset, a sectional chart, and the E-6B.

The E-6B resulted from several years of development by Naval Lt. Philip Dalton in the late 1930s. When the design was finalized, the “E-6B” was introduced to the Army in 1940 and, after Pearl Harbor, the Army Air Forces placed the first large order. The E-6B was widely used during World War II, with more than 400,000 units being built.

The current E-6B looks almost exactly the same as the first one manufactured 80 years ago. The only difference is that lighter materials, such as cardboard, aluminum, and plastic, are now used instead of the original steel model.

The front side of the E-6B features a logarithmic slide rule which performs basic multiplication and division. The “whiz wheel” performs practical conversions between different units: gallons, miles, kilometers, pounds, minutes, seconds, etc. If the user needs to calculate the weight of a certain amount of fuel — for weight and balance — s/he simply positions the wheel at the exact amount and looks at the corresponding value. The front side also contains windows for variations when converting calibrated airspeed to true airspeed or indicated altitude to true altitude.

The backside features another slide rule and wheel designed for computing ground speed and wind correction angle. It provides a graphic method of solving problems in trigonometry and displaying the answers in an accessible form.

Later, when I took the required FAA written exam, the only tools allowed during the test were a basic electronic calculator (one that cannot be programmed) and the E-6B.

It made it to the 23rd century: In the Star Trek episode “The Naked Time,” Mr. Spock uses a handheld E-6B to calculate the time of impact of the Enterprise with a planet. In the episodes “Mudd’s Women” and “Who Mourns for Adonais?” he is again seen holding an E-6B.

Today, most active pilots use more sophisticated tools for flight planning, including software and websites that make the calculations. The E-6B, however, is still the primary computing device in use during initial flight training.

HP-12c, the standard of financial calculators

Dennis Harms, a former Iowa farm boy who joined HP fresh from Iowa State with a Ph.D. in numerical analysis, led a team that produced probably the most successful product of the time, one that, 40 years later, it is still selling in its original form and is used by over 100 million people worldwide. I’m talking about a pocket-size device that revolutionized how financial calculations were made, the HP 12c Financial Calculator.

Original HP-12C Financial Calculator

The HP 12c is a consumer electronics product that is still sold with the original model name and has not changed its design in the last 40 years. A newer version, the HP 12c Platinum, was introduced several years ago. Still, most HP 12c users rejected it: it was not built the same way!

One of the main reasons for its success is the way it was designed at that time. It is no secret that Bill Hewlett was a big fan of calculators. Harms believes the 12c’s success resulted from an uncompromising quality and enormous amount of work and forethought. And 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 from 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 many people like the 12c; RPN is how all calculators should operate.

The HP 12c is so popular that there are several emulators for smartphones and tablets, including an official app from HP for the iPhone. “It can’t be mere 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 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 website. It was written in 1981, and it is an excellent book on financial calculation worth reading.



Pablo Valerio

Tech Analyst and Journalist, engineer. Based in Catalonia, covers Telecoms, Semiconductors, and Supply Chain. and