October 16, 2011

Yes, the answer is Chuck's ridget stays in the air for 9.2843 seconds

I’ve previously written a blog post describing how my love of Hewlett Packard calculators< started with an HP15C calculator bought in the summer of 1982. One of the reasons I’ve stuck with the brand so long is that having learned Reverse Polish Notation (RPN) it’s now second nature and I can’t easily switch to anything else. HP have recently released a modern Limited Edition version of this calculator to celebrate the 30th anniversary of its sister calculator, the HP12C (Wall Street’s cult calculator).

The HP15C and HP12C were part of a series of calculators including basic scientific calculators plus specialist calculators for business, computer science and maths. This family of designs, known as Voyager’, shared the same mechanical form factor and also became celebrated for their extraordinary battery life. The HP15C included built-in functions to perform complex maths such as calculating with complex numbers, matrix maths (even matrices of complex numbers), solving the roots of equations, and numerical integration.

The HP15C has remained so popular that over 15,000 people have signed an online petition to bring it back into production and have sold on eBay at very high prices.

The new HP15C LE recreates the original HP15C, using a modern ARM processor and emulates the original HP15C firmware. As a result the battery life is going to be nowhere near as good but it is fast!

The manual includes an example of root finding based on widget hurler Chuck Fahr (geddit?) and the need to solve the equation below in order to work out how long the widget stays in the air.

Root solving

Where the original HP15C takes around 25 seconds to solve this equation, the new machine takes less then 1 second. I’ve seen benchmark tests that show it running 50 to 100 times faster in general.

Overall, it’s an impressive recreation of a classic design.


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