It’s about time I introduced the first Hewlett-Packard calculator I ever bought. Unlike the previous calculators I’ve shown (Litton Royal 5T, Casio SL-800, Casio ML-81) which were replacements obtained long after the originals had been lost or thrown away, this is the actual calculator I purchased and used back in 1988. I can’t remember the cost, but it must have been enough that I also splashed out on the deluxe leather case to protect it. These days they go for about $150 on eBay for one in good condition with manual and standard case.
This machine is a killer scientific (and business) calculator. It not only has your usual scientific functions – trigonometry, hyperbolics, logarithms, powers – but also probability and statistics, date arithmetic with both normal and 360-day calendars, different base arithmetic (decimal, hex, octal, binary), and Time Value of Money (TVM). It’s not programmable, but instead had a powerful Solver function – enter some formula with variables, enter (all but one) values for the variables, and it would solve for the unknown. There’s even a menu system so that the buttons stay simple visually and are not too overloaded. Peculiarly perhaps for an HP calculator, it used algebraic entry (spot the parentheses and the equals button) and not RPN (Reverse Polish Notation). It even printed via infra-red to an external HP 82240A printer, if you had such a wonderful beast (I didn’t). It was the “do-everything” calculator of Hewlett-Packard’s range at the time, and it hasn’t been equaled since.
In HP collector terms, this is a Pioneer calculator. Others in the Pioneer range (all of which I’ve now bought to fill out my collection) are the 10B, the 14B, the 17B (and its successor, the 17BII), the 20S, the 21S, the 22S, the 32S (and its successor, the 32SII), and the 42S. (B stands for Business, and S, Scientific, although the 21S is a “Stat/Math” calculator.) All have the same shape, have the same keyboard layout (although the colors and legends on the keys were different) and took three chubby Duracell LR44 cells (or equivalent). Although the display size was the same across the range, the display itself varied from a single line segmented LCD display to the two-line matrix display on the more expensive ones, like you see here.
The Solver function was available over several calculators, including the prodigious top-of-the-line clamshell HP-19B (and 19BII). Consequently HP published several additional advanced manuals for these calculators to help you with Solver calculations in various vertical markets. For the 27S there were step-by-step manuals for personal investment and tax planning; real estate, banking and leasing; business finance and accounting; marketing and sales; and technical applications. Even today, these manuals are a great embodiment of formulas and how to perform calculations to minimize the error bars.
I bought it at the point in my programming career when I was starting to develop advanced trading software for swaps and similar financial instruments, hence doing a bazillion present-value type calculations. The date calculations and TVM helped enormously here to check my code and my results. Whereas others around me used HP-12Cs, I plugged away with my trusty 27S.
It really has to be my most favorite calculator ever. I still use it, albeit infrequently now. It really is a fabulous machine, even though it’s now 24 years old.