Old HP calculators and programming quality

Old HP machines!

We’re now in the wake of the new major release of Mac operating system, Yosemite. There will be a number of new features but also correction for many small errors of the previous software. This is typical of today’s software: due to its own complexity, it is bug-ridden, and unsafe in many respects.

Compare that with the 12k * 10 bit of the assembly code of the HP15c. That code was crammed with fantastic mathematical routines that allowed that calculator to perform matrix operations, integrals and solve formulae. Most of the HP15c that have not been physically battered are still working. And talk about battery life. Around 8 pm I receive a 10% battery left message from my phone, while the original HP15c could last up to 15 years with the same battery pack. It could not be upgraded, but there was no need to: it was the ultimate pocket calculator, with everything a science practitioner would ever need, short of a true computer.

Wherever I look into the logic of the HP15c, it seems to me one of the best objects ever designed by mankind. It is the ultimate “less is more” machine. Apart from all keys having three written functions on it, some of them have more: the same key has completely different meanings depending on what you’re doing.

It had 10 digit precision, which was state of the art at the moment for a pocket calculator. Nowadays 14 and 16 digit are normal - however, when in reality you may need short accuracy? And it is not so important the number of digits, but the number of accurate digits. And the HP calculators of that era had absolutely first class algorithms. Most were create by Mr. William Kahan. They were created in machine code, so that it could run as fast as possible with the hp15c hardware.

It used a version of the nut processor (the same as the HP41c), running at an speed that appears ridiculous today: 244 kHz (yes, not MHz), and it took several minutes to perform a 8x8 matrix inversion.

The algorithms were so good that, when HP started the project to reissue the HP15c based on new, modern hardware, they decided to use exactly the same firmware, running on an emulation layer on an Atmel ARM-type processor. There have been several problems in adapting the old firmware to the new hardware - the pause function does not work well, and the low battery indicator does not function in time - at least for me.

But apart from that, it is as good as the original - just 100 times faster!

It is a pity that there are no more stocks of either one!

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