Saturday, November 30, 2013

Vive le HP-97

I just finished building a bookcase with a shelf for my antique calculators, so I got the calculators out of storage, cleaned them, and fired them up.

I don't know which one's my favorite, but this HP-97 is in my top three. According to the serial number, it was built by HP-Singapore in March 1978. This thing was $750 new. I guess people used to steal them, because it has a heavy-duty fitting for chaining it to your desk. I got this one for free from the surplus warehouse of The Aerospace Corporation back when I worked there.

The rechargeable battery pack is long demised and too expensive to rebuild, but the calc works just fine on a 4.8V travel adapter from an old LG phone. You shouldn't run most HP calculators without a functioning battery pack, because the batteries help regulate the current, but the HP-97 does this internally. Plus, the LG adapter is just barely able to run the calc (the "low battery" light glows) so it's safe.

This model went out of production in 1984, but I saw old-timers using them to do solid rocket ballistics calculations in the early 2000s. They used a company-written program stored on magnetic cards that could be read by the calc when passed through the slot to the left of the display.

So what did you get for your $750? First of all, you got a very durable, professional-grade piece of equipment. The keys have a solid, high-quality feel and they all work fine on this nearly 36-year-old calc. The card reader doesn't work any more due to a rubber roller that tended to dry out and fall apart after many years. I recently fixed an identical roller on an HP-67 but haven't done it on my -97.

The best part is the thermal printer. 36 years old and it still works! Heck, the paper is probably 20 years old! This calculator was manufactured right around the time I started using computers, and in that time I've probably gone through 8 printers, but this one keeps on chugging. Mind you I only play with it about once a year.

I just printed this

This is a programmable calculator. To program it, you essentially store the sequence of keystrokes that you would use to solve a problem manually. It has looping, branching and I/O instructions like any language. If you don't store the program on a magnetic card, you have to re-enter it every time you want to use it. Turning the calculator off erases its memory. Programs and data were stored in separate parts of memory - you could save 224 8-bit programming steps and 26 numbers. That amounts to about one-quarter of a kilobyte.

It's interesting to contrast the HP-97, released in 1976, with personal computers of the time. In 1976, nothing we would recognize as a PC was available for the home market, but the very next year brought the Apple II, the Commodore PET and the TRS-80. Each of those would have cost you more than $750. But within a couple of years, for that price you could get an Atari 400 with 8K of memory, plus a nice dot-matrix printer. The Atari would drive a TV display with full-screen color graphics, compared to the HP-97's single line of red LED digits. But the HP-97 remained in production until 1984, the year of the Mac! You can see that HP was following a whole different paradigm than the PC industry. HP was making industrial equipment for Serious People, not home entertainment gadgets.

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