HP 20S


Is the HP 20S calculator still available?


Very available. No longer in production.


Not retail. You can still find either from ebay or profiteers (retailers who still carry at higher than retail prices, although it isn't heavily marked up).

If you are desperate for a compariable calculator the Hp33s is similar in its algebraic mode and has lots more features and functions for somewhat less than you will find a new Hp20s for.

The Hp30s is Hp's replacement for the Hp20s. It is a step down if quality and is NOT programmable, but does include a solver with 6 variables, which is easier to use for quick simple programming.

Neither the HP33s or the Hp30s are of the same quality, although the Hp33s does have a tactle keyboard that will feel most like the Hp20s and it is programmable far beyond the Hp20s.


The 30s is a toy and not worth buying.

The 33s is good.

The 20s can be bought from ebay or from samsoncables.com

You should be able to spend less than $40 and get a good one with manual, if you are patient.

The similarity between the 33s algebraic mode and the 20s is only in the basic operator paradigm--namely infix for + - / X and two number functions, and postfix for 1 number functions. The swap and last are different on the two machines, and the 33s has a two line display, and shows the whole entered expression on the upper line.

Edited: 5 Apr 2006, 1:57 p.m.


I bought one a while ago and quite like it - even if it is AOS. It makes for a good working calculator - for about 20 bux. It is a fine continuance of the HP tradition, even though it has some garingly obvious annoyances (a large horizontal "INPUT" key?) in number handling.

Just a question however, as I did not receive a manual with the calc. Does anyone know how to access the "built in library"? I can't seem to figure it out, and unless I am missing something really basic, it seems somewhat obscure.

Failing that, does anyone know where I can obtain a electronic copy of the manual?

Thanks in advance.


Just a question however, as I did not receive a manual with the calc. Does anyone know how to access the "built in library"?

Thats the easy part: In program mode, LOAD X, X=A..E copies a function from the library to program memory where it can be executed. Only one function can be used at a time.

More difficult: To understand what the functions do and how to prepare the input (or read the output), you need the manual;(.

The HP-20S manual is on the museums DVD.


Thomas R. posted,

More difficult: To understand what the functions do and how to prepare the input (or read the output), you need the manual;(.

That, really, is my main gripe about the HP-20S and HP-21S -- the loadable keystroke programs for useful functionality that I'm sure was touted on the package. It's a case of marketing prevailing over good design.

As Tom pointed out, the HP-20S loadable functions -- such as "root", "int" and "3 by 3" -- are not very intuitive, which is an attribute of the built-in SOLVE and INTEG functions and matrix operations on the HP-15C released six years prior. One must repeatedly consult the HP-20S manual, which may even be forbidden as unauthorized printed material in a test setting.

But there's a more fundamental problem with "root" and "int": When the functions are loaded, the previous contents of program memory are cleared! Now, these loadable functions require a user-defined program to execute. Let's say that the user has programmed a mathematical function, evalulates it at a few points, then wants to solve or integrate it. Load "root" or "int", and poof! goes the user's program. Not very smart, huh?

Contrast that with the HP-15C, where all of its functionality is complementary.

-- KS


does anyone know where I can obtain a electronic copy of the manual?

I was about to draw your attention to this site where manuals in Spanish and Portuguese were available not long ago. I don't speak either language, but nevertheless I could get the info I needed from the Portuguese version. So fair chance that that would go for you as well.

But they have gone. Cannot think of any reason for HP to remove this valuable stuff. Pity.

Lucky me to have downloaded the manuals in time. Interested?


Maybe they want to sell new calculators and think that unsupport will enable sales.


I use the HP-30S at school for my students and it is better than TI, sharp and casio. And it is the only "cheap" "programmable" calculator on the market for less than 20$...



My problem with the 30s is that its memory is friable. And having to hit shift answer on a "formula" format system is nearly as bad as the idea of making the equals sign a shifted function. The memory gets wiped out by merely taking the case on and off. Apparently it must have a poor battery contact design or something.

But the more substantial "toy" aspect is the whole logic. Gee, let's make these cute little variables a,b, x,y, etc and some of them can be used to hold "formulas" and then we'll put a simple quadratic solver and that will make a good "educational tool." And we'll send it out with a one sheet "manual." It makes my skin crawl. For the same cost, the machine could have had a general purpose solver, it could have had a proper number of variable and registers (say, 20 registers, 10 minimum)and yo ucertainly should not se the memory wiped out all the time!

The nicest part of the design is the screen--very readable--better than the 33s by far.

Edited: 6 Apr 2006, 9:05 a.m.


The 20S is also one of the last HP calculators to have a legible color scheme. I have trouble reading the legends on the newer models like the 33S and 49G+. Who thought it was a bright idea to use a shiny metallic finish on the face plate?



Is the HP 20S calculator still available?

Hi Al. You can find a NIB 20s at:


Note that they also advertise a 17bii for sale.



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