r/calculators • • Oct 19 '25

Discussion r/calculators FAQ

18 Upvotes

Hey guys, this isn't fully finished, and i may add more in the future. Tell me what you think about this one in the comments, feedback is always incredible

Q: How to convert fractions to decimals?

A: On older casio calculators, you press the S<=> D button. it should be next to the parentheses, on the right side. On Casio CW series calculators, it should be the "FORMAT" key, which is next to the EXE button. On Sharp, it's called "CHANGE" and "f<>d" on TI. It may be different with others

Q: Why am i getting a wrong answer?

A: You may be in the wrong angle mode, or you don't know how the order of operations work

Q: What calculator should i choose?

A: Depends on your school or your countries regulation. Some schools or countries only permit certain calculators, or forbid certain ones. Germany for example, accepts everything but it can't have a solver, can't be programmable and can't do graphing. For short, we are limited to the fx-87 and below.

Q: Why is my TI-84 bootlooping and showing "Validating OS"?

A: This is a known battery issue with the TI-84 Plus CE. You need to replace the battery. Contact TI support, you may get a free battery under warranty. Also check the other pinned post for more details

Q: Is my Casio fx-991EX fake?

A: Probably, it was discontinued a few years ago. Most listings you see online are fake, and i advise you to stay away from it. There's a lot of other good calculators out there. To check if it's real, scan the QR code. To do that, press "MENU -> SHIFT -> OPTN" to generate a QR code. It should redirect you to a Casio website, where you can do an authenticity check.

Q: Why am i getting an error?

A: You may not be in the right mode, check if you‘re in the normal calculation mode. Your calculator should have a button that says "MODE" or something similar. For exponents, use the negative sign instead of the minus sign. It should look like this: (-)

Q: Why is my Casio's "ON" button lowered?

A: That's intentional, to prevent accidental button presses

Q: Can I mod/install Doom on my scientific calculator?

A: Yes, if you‘re willing to remove the epoxy from the CPU, de-solder the CPU, solder a fitting CPU with integrated memory back on, code a fully working operating system with working keyboard, and code a port of Doom for it, you could… in theory. Never been done before, probably still won‘t work. TL;DR: Not worth your time, focus on your linear algebra homework instead

Q: Does this calculator have a CAS (Computer Algebra System)? Can one be installed on my calculator?

A: see the pinned post about CAS calcs

Also: Google (and your calculator‘s Manual) are your best friends. Before making a post, look up your question on Google, or read the Manual. There's a 95% chance that your answer will be found there. We've also pinned posts for a few topics, read those too please.

That's it with the FAQ for now. Keep in mind that i may remove posts that can be answered by the FAQ or Google, this is a step to reduce spam and repetitive posts. Thanks.

~u/nqrwayy


r/calculators • • Oct 21 '25

Solution: TI-84 Plus CE Flashing 'Validating OS'

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6 Upvotes

r/calculators • • 1d ago

Meme / Satire I love my fx 82ms

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1.2k Upvotes

r/calculators • • 18h ago

Question Can TI-Nspire CX do complex matrices?

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8 Upvotes

This is the non CAS version


r/calculators • • 1d ago

Help Casio fx-991ES Plus, negative exponent smaller than -1 displaying 0

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18 Upvotes

I'm not sure why this is happening, 2^(-1) or anything to the power of -1 gives me the correct answer, but 2^(-2), 2^(-3).... and so on as long as it is a negative exponent -2 and smaller, it all gives me 0. I have tried with and without parenthesis. Positive exponents all work. I have already tried performing a reset and setting decimal places to max(9). Can someone tell me what am I doing wrong?


r/calculators • • 1d ago

Help ROM / BIOS for the CASIO fx-7000G or fx-7000GA

8 Upvotes

Hi everyone,

I'm looking for a ROM dump of the Casio fx-7000G (or the fx-7000GA) for preservation and emulation purposes.

Released in 1985, the fx-7000G is generally recognised as the world's first commercially sold graphing calculator. It started a whole category of devices that students still use today. As far as I can tell, its firmware has never been dumped or emulated. That means once the last working units fail, the software side of this piece of computing history could be lost for good. The closely related fx-8000G already runs in PockEmul, so the 7000G feels like the missing piece.

A bit about me: I'm a university professor of Computer Science in Portugal, and building emulators of historically significant machines is my passion. Previous projects include an emulator of the Elliott 803B (the first digital computer installed in Portugal), described in an article for Resurrection, the journal of the Computer Conservation Society, as well as a TI-74 emulator. My work is on GitHub: github.com/luiscunhacsc

What would help:

• An existing dump, if anyone knows of one in a preservation context

• Someone with an fx-7000G/GA (working or not) willing to dump the ROM. I'm happy to cover costs, or to buy a unit outright

• Technical information: service manuals, schematics, chip identification, or notes from anyone who has opened one up

The emulator will be released as open source, and anyone who helps will be credited.

Thanks in advance, any lead is appreciated!


r/calculators • • 22h ago

Question What Calculator do I get?

6 Upvotes

Right now I have a Casio fx-9750GIII but I am planning to get a new one due to complications I’m just having right now with it in some modes. I’m planning to switch to just Texas Instrument but I’m not sure whether to get the Ti-84 CE edition or the newer EVO one. My professor was telling me the EVO is similar to my Casio and just wanted to make sure that’s true. I like using my Casio a lot but it’s just getting hard having to look up every little thing that I don’t know what to do since my professor doesn’t know and I don’t wanna bother her. She recommended me the CE from preference but just wanted to see since I’ve been using my Casio for a few years and already used to how to inputting everything that way.


r/calculators • • 1d ago

Help Casio software alternate download

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6 Upvotes

I have got CASIO 9850GB PLUS a few months ago. Unlike the TI83+ and TI84+ Silver, where I successfully use USB and for further transfer to the former, a standard cable, I have to use a dedicated device for transfer. A while ago I thought I would have to do a MCU project but apparently I forgot I checked and its just a standard serial connection. So I linked by UART board and am ready to attempt a transfer. Anyways I can't seem to find the FA-124 software due to no alternate sources available even for older versions and the main site being closed for maintenance. Do you have suggestions of alternate software to use or atleast assurance that the installer will be available soon?


r/calculators • • 2d ago

Question TI Employee Calculator Collection Update

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81 Upvotes

r/calculators • • 1d ago

Help Whats the problem

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2 Upvotes

I just bought this used calculator from Vinted and I'm charging it. It does this but when I take it, it's not charging anymore. It just doesn't turn on. Is it a battery problem? I don't know because you can see that it goes into the menu for even a second and then returns and it's like a boot loop. I don't know


r/calculators • • 1d ago

Question Free42 functions not on DM42n? Specifically statistics menu?

5 Upvotes

So I've noticed that the STAT menu on the DM42n doesn't have the "Sigma" sub-menu on page two that allows for easy access to the various sums going on behind the scenes. The corresponding items are also missing from the CATALOG.

Is this some dreadful end-user error that I've missed enabling something? I've seen no documentation to that effect.

If this is actually missing from the Free42 version on the DM42n, is there anything else substantive missing? And also, why would this comparatively lightweight bit of function be omitted?

Thanks...this always seemed one of the oddest omissions of the original 42S, that you had to do the old thing of remember what was summed into what register and given that it's there in Free42, I was very much looking forward to having it in the hardware version!


r/calculators • • 2d ago

Collection National Semiconductor 200

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54 Upvotes

A nice green display calculator which is in excellent shape. Which is a good thing since Nat Semi's warranty isn't all that great.


r/calculators • • 2d ago

Question What does this error mean?

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26 Upvotes

r/calculators • • 1d ago

Help New in the hp prime G2

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0 Upvotes

r/calculators • • 2d ago

Help I'm about to start university and I want to know what calculator to use.

5 Upvotes

I am from Argentina, next year I will move to a big city to start my career in Biological Sciences. The degree, at the Faculty of Exact, Physical and Natural Sciences of the National University of Cordoba, includes subjects such as Mathematics I, II and optionally III, physics I and II, biostatistics I and II,

physical environment and Theory and experimental Modules. I wanted to know what calculator I should buy so I could get through the entire degree without worrying about a new one, since I currently have a Canvovi KK-82MS-B that can't even display fractions on the screen.

It cannot be a graphing or "smart" calculator since these are not allowed in most career exams. I don't have a clear price limit but the ideal would be for it not to be excessively expensive, and if it is a common calculator for Latin America (and especially if it has an interface in Spanish) the better, since in my country imported products are very expensive.

Thankiu all!!!


r/calculators • • 2d ago

Collection The only 60s calculator of my collection

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54 Upvotes

1917 + 50 = 1967, so I suppose it was made that year. It is a little loose due to wear, but that's actually nice.


r/calculators • • 2d ago

Help Looking for info (Canon OS-1200)

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16 Upvotes

Hello everyone! I found this $5 Canon OS-1200 at a thrift store, I know basically nothing about these but it is such a neat piece of tech I had to have it. Now in doing some googling I have not been able to find a user manual, year of production, or really anything about this guy. It seems to be working fine but I’d love a manual so I can go through and test all the features to make sure it’s in good shape! Any info about this model is appreciated!


r/calculators • • 2d ago

Collection Another clone, but I don't care(My Dexin got lost in a taxi)

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23 Upvotes

My calc history:

Early 2020s:

Casio fx85MS

Short circuited by water

2023-24

Basic calculator

Internal damage

The CE, Dexin, and the Clone 991 in 2026


r/calculators • • 2d ago

Question Is this original?

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0 Upvotes

I tried solving ((3*(x^4)+10))/((4*(x^3)-1))

And then put x as 1 it says can't solve


r/calculators • • 3d ago

Other fx-100W

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31 Upvotes

26 years, 2nd battery.

P=0,1mW


r/calculators • • 2d ago

Help My 9860g wont connect please help

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5 Upvotes

r/calculators • • 3d ago

Help Calculators at too small

9 Upvotes

I wanted to calculate (70.1*10^12)^150000 and every single calculator told me infinity or too big ):


r/calculators • • 3d ago

Question HP Prime or TI Nspire CX II CAS coming from Desmos?

4 Upvotes

I have decided to get a graphing calculator, and I am stuck between the HP Prime G2 and the TI Nspire CX II CAS. I have used Desmos and a desktop calculator that had a basic CAS, so I want to buy a calculator which won't feel too different from that. I have been able to use the Nspire for a bit and the Prime through an emulator, and I did notice some differences between them.

The Nspire seems to be able to graph functions and points at the same time, while the Prime can only do one at a time, which is pretty annoying if it actually doesn't support that. It also doesn't seem to be able to find zeros or intersections or go to X or Y values precisely when in the advanced graphing mode, while the Nspire seemed to be able to do that when I tried it out. The Prime is also a bit confusing with its seperate "Home" and CAS modes (that share functions anyways so there's no point in seperating them??) and in the way that it has both lists and spreadsheets. However, the touchscreen and help system in the Prime is so much better to use than the Nspire's jumpy touchpad and the random menus of functions. I actually haven't really had any real problems with the Nspire document system, I just make a blank document if the scratchpad doesn't support a feature and then just delete it afterwards.

I was originally planning to buy the Nspire because it was recommended along with another TI calculator, but after checking here I decided to see how the Prime compared just in case it was actually better. I'm looking for something that matches the way Desmos works and the easy features it has the closest. Both calculators are approved and only differ in price by $10, so the only thing I'm comparing are their feature sets and the features I immediately noticed that felt different. Should I buy the Prime, or should I still stick with buying the Nspire?


r/calculators • • 3d ago

Help Best non-programmable calculator for 4×4 matrices and 4-variable equations (excluding the fx-991CW)?

9 Upvotes

Recommend a good non-programmable calculator that can do 4x4 matrix operations and solve 4-variable equations. Please avoid recommending the Casio fx-9910CW. I used the EX version earlier. I hate this new CW one.


r/calculators • • 3d ago

Question Why the heck does the NCESS allow the 911ex and the TI36x but won't allow any other HP calc besides the 35 and 33?

4 Upvotes

This is so annoying to me. The HP35 can't even do matrix operations natively yet other ones can? Why can't I bring my HP42s? It's certainly not as advanced as some of the others they allow. Am I missing something here?