Here you'll find a set of pictures I've taken myself featuring HP calculators from my own personal collection, together with useful details and my (hopefully interesting) anecdotes and comments on each particular model, including links to relevant materials (Articles, Brochures, Challenges) previously uploaded by me to this very site. Enjoy!
This is my HP-10C, the simplest HP Voyager series' model and the last to be released back in 1982. After 37 years (as of 2019), it still looks and works great.
Unbelievable quality for such modest unit and its very simplicity (just the one yellow prefix key) in the iconic landscape Voyager form factor make it a very appealing calc to behold, I know that I like it very much. And as it didn't sell well it's become a very rare vintage calc indeed, you'd be hard-pressed to find one in mint shape like the one shown above.
Anyway, despite its simplicity it still boasts the same awesome physical quality, including "eternal" battery duration, but it has a much reduced function set and capabilities as compared to the HP-11C (let alone the HP-15C), though still programmable and featuring all the usual scientific and statistic functions (including linear regression), engineering display mode and flexible storage allocation (from 10 storage registers and 9 lines of program memory to no registers and 79 lines).
This is my HP-10C, the simplest HP Voyager series' model and the last to be released back in 1982. After 37 years (as of 2019), it still looks and works great.
See the full description and other details in the link above this one.
This is my HP-10C, the simplest HP Voyager series' model and the last to be released back in 1982. After 37 years (as of 2019), it still looks and works great.
See the full description and other details in the link above this one.
This is a close-up detail of my HP-10C, the simplest HP Voyager series' model and the last to be released back in 1982. After 37 years (as of 2019), it still looks and works great.
See the full description and other details in the link above this one.
Long Live the HP-11C, (includes a program to quickly and accurately find the sum of infinite alternating series, even divergent ones)
This is my HP-11C, the first Voyager I owned, which was given to me back in 1981 as a present by a close friend.
See the full description and other details in the link above this one.
Long Live the HP-12C, (includes a program to play a game of Bridge-It vs. the HP-12C)
Tried and Tricky Trigonometrics, (fits all 6 trigonometric functions accurately in a single program)
HP-12C Serendipitous Solver, (finds roots of, and evaluates, Nth-degree polynomials quickly and accurately)
Long Live the HP-15C, (includes a program to compute Euler's constant e=2.71828+ to more than 200 digits using matrix operations)
HP-15C Nth-degree Polynomial Fitting, (fits an Nth-degree polynomial to a set of data)
This is my HP-16C, a fantastic HP calculator with the outstanding quality inherent to all Voyager Series models, and which still looks and works like new despite being nearly 40 years old by now (2019).
The HP-16 is a specialized calculator intended for programmers (though I've never used it professionally), which natively works in bases 2, 8, 10 and 16 with word sizes from 1 to 64 bits. It features all kinds of dedicated operations such as shift and rotate functions, masking, bitwise logic, double precision multiplication and division, plus standard floating point arithmetic with square root and 1/x, and advanced programming with labels, loops, subroutines, flags and tests. It also has reallocatable memory between program steps and registers where the number or registers depends as well on the specified word size.
Precisely that very feature, increasing the number of available registers by decreasing the word size, is made good use of in this article I wrote dedicated to the HP-16C:
Long Live the HP-16C, (includes a program to solve the Hanoi Towers puzzle with N disks)
This is a leather-like case for all models of the HP Voyager Series, i.e.: HP-10C, HP-11C, HP-12C, HP-15C and HP-16C. It perfectly fits and keeps them well protected besides looking real classy. I got one for every Voyager calc I own plus another one for my HP42S as well. Recommended.
This is my very first HP calculator, the wonderful HP-25, the smallest and cheapest HP programmable calculator at the time. Released in 1975 (some 44 years ago as of 2019) it still looks and works perfectly.
It has 10-digit with 2-digit exponent, classic RPN stack, 8 storage registers with full storage arithmetic, a vast range of math functions including statistics, solid build and very small size, bright LED display fully useable in very low light or even utter darkness, excellent reliable keyboard, extremely good and comprehensive documentation (including tons of good application programs for all disciplnes), good programmability (49 fully-merged steps) with tests, branching, and single-step execution for debugging, etc. Also, an updated version, the HP-25C, dotted it with Continuous Memory, another first at the time.
You'd need to have lived through those times in order to fully understand what the HP-25 meant for both professionals and students like me back then, but failing that, you can find some of my programs for it in the HP Calculator Programs section in this very site, which will give you a fair idea. Also, you should really have a look at this Article of mine for a detailed review including two truly amazing sample programs for you to see for yourself what it could do when pushed to the max:
Long Live the HP-25, (includes two programs to solve 1st-order ordinary differential equations using Runge-Kutta methods of 3rd and 4th order, resp.)
This is my very first HP calculator, the wonderful HP-25, the smallest and cheapest HP programmable calculator at the time. Released in 1975 (some 44 years ago as of 2019) it still looks and works perfectly.
See the full description and other details in the link above this one.
This is my very first HP calculator, the wonderful HP-25, the smallest and cheapest HP programmable calculator at the time. Released in 1975 (some 44 years ago as of 2019) it still looks and works perfectly.
See the full description and other details in the link above this one.
This is my HP28S, a Saturn-based model, the one and only RPL model I own which I bought just because I liked the form factor: foldable with a large graphic screen and twin keyboards, very elegant and ergonomic (save for the dreaded battery door). Right now it's 31 years old (as of 2019) and absolutely mint, matter of fact it's NIB actually, I've never ever used it other than to take these pics.
Back then it was a truly revolutionary model, a quantum leap in terms of paradigm and functionality over anything existing at the time, which essentially doomed classic RPN for good. It does symbolic math, has named variables, lots of data types, a very extensive function set, a powerful Solver, infrared printing, graph plotting, math in bases 2,8,10 and 16 with word sizes from 1 to 64 bits, catalog of all functions with their argument syntax, ... plus directories, custom menu, extra graphics manipulations. Last but most certainly not least, it has 32 Kb RAM instead of the nearly useless 2 Kb of its previous incarnation, the HP28C (which should've never been released with such crippling specification.)
This is my HP28S, a Saturn-based model, the one and only RPL model I own, 31 years old as of 2019.
See the full description and other details in the link above this one.
Behold my NIB (literally!) HP-32S !. Released in 1988, it was an inexpensive ($53.86 here) but powerful calculator, truly small and lightweight, which many (yours truly included) prefer to its sequel (the HP-32SII) for his elegant, non-cluttered keyboard (made possible by its menu system) yet it has a comprehensive function set including hyperbolics, Solver, Integrate, bases 2,8,10 and 16, statistics and complex-number support for arithmetic and transcendental functions. Alas, no complex stack a la HP-15C and no built-in matrix operations either.
Instead of the usual RPN registers, it has 27 variables (A-Z + i for indirection) which are allocated and deallocated on the fly to make the most of its somewhat meager 390 bytes of RAM available to the user for data and programs, which could use up to 7 levels of subroutines, indirection, looping, conditional tests, flags, labeled I/O and last but not least the excellent Solver which could solve for any variable. Also, batteries last for very long (though not as long as the Voyager Series' models, mind you).
One of my HP-32S, a most excellent and much loved classic RPN calculator, small, elegant, lightweight and powerful.
See the full description and other details in the link above this one.
This is my HP-41CX, the best classic version of the HP-41C, a revolutionary alphanumeric model every HP-calc fan craved for at the time of its release some 40 years ago. I certainly did so I sold my beloved HP-67 to buy one and did wonders with it (synthetics !), both for fun and for profit. The 41CX is depicted here with its mandatory (if power-hungry) card reader and both Advantage and PPC modules plugged in (alas, not seen from this angle). With it and a full 40-card holder or two you had enormous computing power on the go.
The CX, introduced in 1983, was essentially a 41C on steroids: built-in Quad Memory module, Extended-Functions/Extended-Memory module, Timer module, plus text editor and extra functions not available anywhere else, while leaving all 4 ports free for other uses (e.g.: Advantage module, PPC/HEPAX/ZENROM module, Card Reader and Printer, or additional Extended Memory). A Classic-Dream-Machine if there ever was one, with dozens upon dozens of application-specific modules, Solution Books and dedicated peripherals, both HP's and 3rd-party's.
Have a look at these articles I wrote where the HP-41C is featured (as well as some of my programs for it in the HP Calculator Programs section in this very site):
Long Live the Advantage ROM, (N-th degree Polynomial Fit program included)
Know Thy Foe: A New Contender, (comparing HP-41C vs. SHARP PC-1211, two 41C programs and 6 SHARP programs included)
This is my very first HP-71B, which I got back in 1986 so it's now (2019) some 33 years-old and as you can see it's still absolutely as new and works flawlessly. Here it's depicted with a CMT 128 Kb RAM Memory Module plugged in the card reader port and perfectly matching the HP-71B's looks. I found the included card reader mostly useless for a number of reasons, so I eventually substituted it for the much more useful 128 Kb module, which can hold the equivalent of 200 magnetic cards at once, all of it instantly available.
Before getting this HP-71B I had been privy to a pre-production model before its release (it paid having friends at local HP headquarters !), which was lent to me for a weekend so that I could try it and see how I liked it. In a word, I found it awesome in the extreme, many many times faster than the HP-41C (though still 5 times slower than the much bigger and less powerful HP-75C), 16 Kb seemed like infinite RAM as compared to the HP-41C too (let alone when fitted with the 128 Kb module) and expandable to 512 Kb (in a handheld device !!), awesome HP-IL capabilities for interfacing with all kinds of peripherals and instruments at speeds many time faster than (again!) the HP-41C, the best BASIC dialect you could dream of and incredibly powerful plug-in ROMs such as my all-time favorite, the Math ROM which provides unbeatable math capabilities, even surpassing the full-size PCs of the time.
Thus, I was in love with the HP-71B and as soon as it was released I convinced my boss to get one for me (I couldn't afford the expense) with card-reader and HP-IL module fitted-in, and I bought the Math ROM with my own money (expensive but it had top priority for me, I'd rather not eat). I wrote lots of software for it, both for profit and for fun (lots too !!) and in time got several more HP-71B, this time for peanuts as the second-hand market was flooded with thousands of them discarded by some UK Government agency, so you probably can get one cheap too. Also, there's a number of very good emulators for MS-DOS, Windows and Android, most for free, so you can try one if you want.
Have a look at the following articles I wrote which extensively discuss and feature the HP-71B:
Long Live the HP-71B, (full description and history, includes a Text Stereograms generator program)
HP-71B Modest Mater, (program to solve Mate-in-N chess problems)
HP-71B Math ROM Bakers Dozen (Vol. 1), (many tips and useful code snippets, first part)
HP-71B Math ROM Bakers Dozen (Vol. 2), ((many tips and useful code snippets, second part))
HP-71B Short and Sweet Sudoku Solver, (program to solve any Sudoku puzzle)
HP-71B Sudoku Solver Sublime Sequel, (enhancement to the program to solve any Sudoku puzzle)
HP-71B Sudoku Generator and Coach, (program to generate new Sudoku puzzles and coach you to manually solve any puzzle)
HP-71B Fantastic FOUR, (multiprecision multiplication using Fast Fourier Transforms)
HP-71B Minimax Polynomial Fit, (program to fit a set of data to the very best possible polynomial)
25 years of Othello, (program to play Othello versus the machine)
Small Fry - Primes Acounting, (routine to very quickly count primes on a given interval with excellent accuracy)
Small Fry - Let's Be Rational, (routine to convert reals to fractions and find their continued fracton form)
Boldly Going - Matrix Square Root, (routine to compute the square root of a given matrix)
Boldly Going - Identifying Constants, (program to find the symbolic expression which evaluates to a given numeric value, many applications)
This is my very first HP-71B, which I got back in 1986 so it's now (2019) some 33 years-old and as you can see it's still absolutely as new and works flawlessly.
See the full description and other details in the link above this one.
This is my very first HP-71B, depicted here with a 128 Kb CMT Memory Module plugged in the card reader port which, together with three 4K Memory Modules (not visible from this angle) makes for a whopping total of 156 Kb RAM as shown in the display. This much RAM allows for more than 100 sizable programs kept in memory at once, instantly available at all times, or you can use it to process enormous matrices (up to, say, 135x135 if real or 95x95 if complex) or arrays (up to nearly 20,000 real elements or 10,000 complex ones).
Nowadays we're used to have many Mb or even Gb available in a small handheld device but back in the middle 80's that much memory and processing power in a battery-powered handheld computer which you could use in the middle of nowhere was absolutely unheard of, a worldwide first. Most people couldn't afford the expense so it made little news but a lot of professionals were delighted in the extreme and literally jumped at the opportunity to get it no matter the cost.
Actually, I knew one of these people, who bought several HP-71B (one for actual use and the others as spares, just in case), fitted one with more than 200 Kb of RAM, Math ROM, HP-IL ROM and tape drive and went out to the mountains and other difficult and isolated places whatever the season to interface the HP-71B with a number of measuring devices and take many thousands of measurements on location, to later analyze the gathered data at home and conduct very complex geophysical studies of the terrain. He was paid well enough that the cost of the HP-71B and peripherals was negligible in comparison, their acquisition really paid off.
See the full description of the HP-71B proper and other details in the link above.
This is my very first HP-71B, and here you can see the four frontal ports with three 4K Memory Modules and the Math ROM plugged in. The memory modules, which add 12 Kb to the built-in 16 Kb of RAM, plus the (not visible from this angle) 128 Kb CMT Memory Module plugged in the card reader port, makes for a whopping total of 156 Kb RAM which you could increase even further by simply plugging in third-party 32 Kb memory modules instead of the 4 Kb HP ones depicted here.
Add to that the awesome capabilities the Math ROM provides (complex variables and matrices, complex arithmetic and functions, full matrix operations, Hyperbolic and Gamma functions, Integrate, Solve, Fast Fourier Transform, etc.) and you have the most advanced mathematical and processing capabilities on the go for any device of its time.
See the full description and other details in the link above.
This is a leather-like case for the HP-71B. It perfectly fits, with room to include the Quick Reference Guide and/or some keyboard overlays, and keeps the machine well protected against falls to the floor and impacts, but it has a terrible flaw in the (very) long run: after 20 or 30 years elapse the black mesh which lines the interior will disintegrate into a fine black powder that gets into all places: the LCD, the keyboard, the ports, inside the machine itself. The case can be recovered by thoroughly washing it till there are no traces of the black powder but the process of cleaning the HP-71B, while quite possible, is cumbersome and very time-consuming. The black powder doesn't seem to harm the machine, though.
If you've got one or more HP-71B insides these cases right now, you'd do well to inspect them carefully, and either store them out of the cases or place them inside hermetically sealed plastic bags inside the cases, to prevent the eventual disintegration's nasty effects.
These articles, programs, pictures, their descriptions and other materials created by me are (c) Valentin Albillo, and can be used freely for non-profit purposes as long as (1) the contents aren't modified in any way and (2) the copyright is acknowledged.
In plain words, you can download them and use them for non-profit purposes but do not include them in any media and/or site for which you're asking money, do not tamper with their contents and do not say or imply that you created them or that you don't know who created them, you must always give due credit to the copyright holder (that's me).