HP 17B, 27S Precedence (order of operations)


(Note to Dave: I come to this website EVERYDAY because of it's highly-detailed content on my prized HP's. This post is not meant to be nitpicky or petty. It is mearly an observance I stumbled across during my own calculator comparison. Keep up the GOOD work; we appreciate it! Matt)

There may be a discrepancy in the MoHPC descriptions of the 17B and 27S Precedence operations. The following two sentences can be found in both of the 17B and 27S calculator descriptions:

"The calculator used a rather nice form of algebraic logic in which pending operations were left in the display. For example if the user pressed 1+2*3, the calculator would show that expression in display."

Using my own calculators, I find the description only applies to the 27S. The 27S follows arithmetic precedence as described. Upon pressing the "*" (multiply) key on the 17B, "1+2" is evaluated to 3. In other words, the 17B doesn't recognize arithmetic precedence. In Alegbraic mode, my 17BII works just like the 17B.

Just to make sure I wasn't me making a (another) mistake, like a some kind of flag setting (there are no "flags" on these calculators :-), I checked the owner's manuals of all three calculators, concerning Priority of Operators, Precedence, Arithmetic Priority, etc.. Only the 27S manual (page 44) specifically says "The 27S uses a system of operator priority to evaluate expressions", then goes on to list the highest to lowest priority (y^x, then X and /, then + and -). I cannot find a similar sentence in either of the 17B/17BII manuals.

However, both the 17B and 17BII, do use precedence in their Solver applications. On page 142 (both manuals), the following footnote can be found "Because the Solver uses arithmetic priority (x, / before +, -), a second set of parentheses... is not necessary.".

Is the 27S the only Pioneer that observes "order of operators" precedence? Am I doing something wrong? Inquiring minds want to know ;-)

Thanks again for this website,


You are correct in your observation of the 17 vs. the 27. Precidence is also lacking on the 19(the closest thing on the market to a 27) also. However HP also produced the 20, 21, and 22s models that were algerbraic and had precidence. The 22 was also a dot matrix display but with one line only. It is my opinion that the 27s was Hp's 2nd best calc ever made. The first? An HP42 of course.

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