The Museum of HP Calculators

HP Memories Forum

HP-35 vs Slide Rule

Posted by Bob Hermann on 28 Nov 2001, 3:51 p.m.

In 1972, I was taking engineering classes at Cal State Northridge. One of the guys in my classes had bought one of the first HP-35's (red dot) for \$395 directly from HP (he worked for Lockheed and they had a direct line to HP). He definitely had an advantage with that calculator over the rest of us using slide rules and trying to maintain the location of the decimal point while performing iterative calculations during tests.

The next year he just had to have the new HP-45 (it sold for \$395 and I believe HP dropped the price of the HP-35 to \$295). He sold his "old" HP-35 to me for \$175. That was a bit much in those days but it was a much better calculator than anything else around.

It was a dream come true and I sailed through engineering school. The University debated banning calculators but never got around to actually doing it.

I used the same calculator for about ten years during my first years at Bechtel Corp. as a Mechanical Engineer. I also was able to use it during the P.E. exam.

One real nice thing about the first HP's was that people quickly learned not to ask you if they could borrow it. The lack of the equal sign was very intimidating and most never got over that initial shock. (RPN did have another advantage.)

One minor glitch that did come up after all those years was that one portion of all the LED's went out. The problem was that you did not know if any of the digits was a 5 or a 6 and an 8 or a 9. I used a work around for a while by subracting a 1 from the affected digit to determine its correct value. For example if the screen showed 51491, I would subract 10010 from the display. If the result was 51491, then I knew the screen had actually displayed 61491. If the result was 41491, then the original display was 51491. After tiring of this, I finally gave in and bought a full function Casio for about \$25. (By that time I was fully AC/DC and could easily go from RPN to the "Dark Side.")