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HP-35 blind buy but buggy! - Max Stone - 11-11-2013 So I'm now the proud owner of a Ver 2 HP-35 in excellent condition. My first HP-35. Any ideas?
Here's a pic next to its younger brother: Edited: 11 Nov 2013, 4:15 p.m.
Re: HP-35 blind buy but buggy! - Michael de Estrada - 11-11-2013 My buggy HP 35 V2 does the same thing. My HP 35 V4 w/o the bug does the same for 3^2 but is slightly different for 2^3 which results in 8.000000002. I wouldn't call this a bug so much as roundoff error.
Re: HP-35 blind buy but buggy! - Max Stone - 11-11-2013 OK, so it's not cosmic radiation! It's such a small error that 2^2 (3.999999999) then sqrt rounds back again to 2. I guess moving up from a slide rule in 1972, these tiny errors could be forgiven. (Whereas the 2.02 ln ex bug was a fairly large error of 1%).
Thanks!
Re: HP-35 blind buy but buggy! - Max Stone - 11-11-2013 Just tried my HP-80, and guess what...2^2 is 3.999999999 if you view beyond 6 significant places (i.e.: shift 7). Must be a rounding feature in the Classic series?
Re: HP-35 blind buy but buggy! - Eric Smith - 11-11-2013 That was considered to be limited accuracy, not a bug. See the article "The new accuracy: making 2^3=8" by Dennis Harms in the November 1976 issue of HP Journal. The early HP models didn't have enough ROM space for better algorithms. Things were improved considerably in the late Woodstock/67/9x era.
Re: HP-35 blind buy but buggy! - Max Stone - 11-11-2013 Thanks Eric - I'll dig out that article.
Re: HP-35 blind buy but buggy! - Max Stone - 11-11-2013 Re: HP-35 blind buy but buggy! - Dieter - 11-11-2013 Quote:This is not a bug but simply the consequence of limited accuracy. Unlike later devices, the 35 did not use additional digits for internal calculations. It displayed 10 digits, and that's what it used internally. Since powers are evaluated as e^(exponent * ln base), this is what you get with 10 digits: 3^2 = e^(2 * ln 3) = e^2,197224578 = 9,0000 00005 974...That's why HP later added three more digits to overcome this limitation (well, at least in most cases). The respective HP Journal article has been mentioned already.
Dieter
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