Terminated: 1975
In a time where other, often quite expensive, calculators could only do the standard four functions and sometimes a square root, HEWLETT PACKARD was able to proce this beautiful calculator. This calculator doesn’t have the complex look of later HP calculators because there are only three keys with double functions, ARC SIN, ARC COS and ARC TAN.
Talking about those functions, there is only one angular mode available, DEGrees. Maybe an odd decision since PI is also available as a constant. Still, being able to produce a pocket calculator with these functions at all is a feat in 1972.
Very powerful for its time, uses RPN and includes useful scientific functions such as trigonometric functions and their inverses (using the "arc"-key), natural logarithms and powers (using the "x^y"-key).
As usual with the early HP calculators, this calculator as a very strong case and keys that simply won’t wear out.
The first one shown here is the second revision. The first revision had a power led next to the power slider, which was a bit odd because when the calculator is on, the display also lights up.
The second one shown here (graciously donated by Richard Pilkington of the University of Salford)
is the last revision of this calculator. The markings are now on the keys
themselves. This calculator had a nice tag painted on, it had apparently been in use
at the University of Salford’s Electrical Engineering’s department. I have removed
the tag but took a photograph of it as a reminder. You can see that the
calculator has been used a lot, or at least has been switched on and off a lot, by
the wear on the silver decoration above the power slider.
Something strange is going on with one of the HP 35’s in my collection,
the third one shown here. When I found that one on a flea market I
first thought I had found an HP 80, HP’s second pocket calculator.
On closer inspection however it
turned out to be a HP 35 with a "Hewlett • Packard 80" designation.
According to other sources on the net, such as the
excellent site The Museum of
HP Calculators (link valid 2024-01-13), the designation should have
been "Hewlett • Packard" or "Hewlett • Packard 35" (like the other
ones shown here). I find this very
strange. Since the key placement of the HP 35 and the HP 80 are alike, one
might wonder if this is a front swap, however that seems impossible because
the HP 80’s keys on the fourth row are wider, same as the second HP 35 shown here, and there are no signs whatsoever
of any tampering. The name tag itself does not look swappable either. If
anyone can explain this trange fact, please send me an e-mail.
There’s some information on the HP 35 on HP’s official website (link valid 2024-01-13).
The Hewlett-Packard Company Archives site also has some information on this calculator, see Adding Innovation: The HP 35 (link valid 2024-01-13).
The website vintagecalculators.com (link valid 2024-01-13) has a page with interesting information from the book "A Guide to HP Handheld Calculators and Computers," by Wlodek Mier-Jedrzejowicz. See this page (link valid 2024-01-13).
For more information on this beauty please refer to the better sources, like The Museum of HP Calculators (link valid 2024-01-13).