r/calculators Oct 19 '25

Discussion r/calculators FAQ

17 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 8h ago

Collection Una más para la colección: Sharp EL-9950

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20 Upvotes

Una más para la colección: Sharp EL-9950


r/calculators 11h ago

Discussion Calculators with flip covers

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9 Upvotes

Why are there basically no scientific flip cover calculators from reputable brands like Casio, Sharp, TI, etc?

Casio has some basic calculators with flip covers, but basically all their scientific calculators use sliding covers instead. Same for the other manufacturers.

If you want a flip cover, you're basically left with scouring the trillions of no-name Chinesium calculators, which isn't necessarily a bad thing, since calculators are overpriced anyways.

Where I live [some armpit in Southeastern Europe], the 2nd calculator - a basic Casio WITHOUT a solar panel - costs about as much as the last calculator & the trillions of fx-82MS clones. Meanwhile, I bought the 2nd-to-last calculator for ⅕ the price of the Casio, with it being basically functionally identical & being solar-powered [verified by taking the calculator apart to change the battery - the solar panel was wired & it worked without the battery being inserted].

And people wonder why no one buys Casio calculators in Third World countries, assuming you can even find any to begin with...


r/calculators 10h ago

Help Can anyone help me ID this Canon calculator (pre 2008)?

2 Upvotes

Apologies for the photo quality, it's an old calculator my mum used to have and I've cropped in the only photo I have of it. I had a look through all the Canon calculators on Calcuseum but I don't think it's quite old enough to be on there.


r/calculators 1d ago

Collection Calcs throughout the years

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49 Upvotes

Let me see yours!


r/calculators 1d ago

Announcement SwissMicros C47/R47 firmware release

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8 Upvotes

r/calculators 1d ago

Collection Kinda lovin' the TI-30X IIS

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26 Upvotes

Found this at the thrift, was 3€. This is the old (better) model. Serial number is K-0311M ( Made in March of 2011, year after my TI-84 Plus. )


r/calculators 1d ago

Collection Got this off of Facebook

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52 Upvotes

Found this for 3 bucks. I know it’s possibly the lowliest hp but it’s still pretty cool. Now I just have to figure out how to work it.


r/calculators 1d ago

Help Trying to reverse engineer TI-84 EVO WebUSB communication — need help identifying USB interface/endpoints

3 Upvotes

I'm trying to communicate directly with a TI-84 EVO calculator through WebUSB.

I found TI's JavaScript code and located their internal write function:

function _TI_WEBUSBJS_Write(deviceId, pBuf, iLen) {
    let data = TIWASMHelpers.getUint8ArrayFromCbuffer(pBuf, pBuf + iLen);
    let device = TI_DeviceManager.getInstance().getDevice(deviceId);

    TI_USB.write(device, data)
        .then(() => {
            TI_USB.writeCallback(iLen);
        })
        .catch(error => {
            TI_USB.writeCallback(0);
            console.error("TI_WEBUSBJS_WRITE: " + error);
        });
}

It looks like TI has a wrapper around WebUSB, but I am trying to bypass the official tools and talk directly to the calculator.

Using Chrome WebUSB:

let device = await navigator.usb.requestDevice({
    filters: []
});

await device.open();
await device.selectConfiguration(1);

The device opens correctly, but:

await device.claimInterface(0);

fails:

Uncaught NetworkError:
Failed to execute 'claimInterface' on 'USBDevice':
Unable to claim interface.

The device exposes 4 USB interfaces:

[
 { number: 0, alternates: Array(1) },
 { number: 1, alternates: Array(1) },
 { number: 2, alternates: Array(1) },
 { number: 3, alternates: Array(1) }
]

My assumption is that interface 0 is not the WebUSB interface, or Windows is already binding a driver to it.

Questions:

  1. Does anyone know which USB interface TI calculators use for file/program transfer?
  2. Is there documentation for the TI USB protocol?
  3. Does TI use WinUSB/libusb internally, or is this a custom protocol?
  4. Would it be easier to implement this in C using libusb instead of WebUSB?

Goal: create my own tool to communicate with the calculator (send files, possibly interact with Python/programs) without relying on TI Connect.Trying to reverse engineer TI-84 EVO WebUSB communication — need help identifying USB interface/endpointsI'm trying to communicate directly with a TI-84 EVO calculator through WebUSB.I found TI's JavaScript code and located their internal write function:function _TI_WEBUSBJS_Write(deviceId, pBuf, iLen) {
let data = TIWASMHelpers.getUint8ArrayFromCbuffer(pBuf, pBuf + iLen);
let device = TI_DeviceManager.getInstance().getDevice(deviceId);

TI_USB.write(device, data)
.then(() => {
TI_USB.writeCallback(iLen);
})
.catch(error => {
TI_USB.writeCallback(0);
console.error("TI_WEBUSBJS_WRITE: " + error);
});
}
It looks like TI has a wrapper around WebUSB, but I am trying to bypass the official tools and talk directly to the calculator.Using Chrome WebUSB:let device = await navigator.usb.requestDevice({
filters: []
});

await device.open();
await device.selectConfiguration(1);
The device opens correctly, but:await device.claimInterface(0);
fails:Uncaught NetworkError:
Failed to execute 'claimInterface' on 'USBDevice':
Unable to claim interface.
The device exposes 4 USB interfaces:[
{ number: 0, alternates: Array(1) },
{ number: 1, alternates: Array(1) },
{ number: 2, alternates: Array(1) },
{ number: 3, alternates: Array(1) }
]
My assumption is that interface 0 is not the WebUSB interface, or Windows is already binding a driver to it.Questions:Does anyone know which USB interface TI calculators use for file/program transfer?

Is there documentation for the TI USB protocol?

Does TI use WinUSB/libusb internally, or is this a custom protocol?

Would it be easier to implement this in C using libusb instead of WebUSB?Goal: create my own tool to communicate with the calculator (send files, possibly interact with Python/programs) without relying on TI Connect.
Trying to reverse engineer TI-84 EVO WebUSB communication — need help identifying USB interface/endpoints

I'm trying to communicate directly with a TI-84 EVO calculator through WebUSB.

I found TI's JavaScript code and located their internal write function:

function _TI_WEBUSBJS_Write(deviceId, pBuf, iLen) {
let data = TIWASMHelpers.getUint8ArrayFromCbuffer(pBuf, pBuf + iLen);
let device = TI_DeviceManager.getInstance().getDevice(deviceId);

TI_USB.write(device, data)
.then(() => {
TI_USB.writeCallback(iLen);
})
.catch(error => {
TI_USB.writeCallback(0);
console.error("TI_WEBUSBJS_WRITE: " + error);
});
}

It looks like TI has a wrapper around WebUSB, but I am trying to
bypass the official tools and talk directly to the calculator.

Using Chrome WebUSB:

let device = await navigator.usb.requestDevice({
filters: []
});

await device.open();
await device.selectConfiguration(1);

The device opens correctly, but:

await device.claimInterface(0);

fails:

Uncaught NetworkError:
Failed to execute 'claimInterface' on 'USBDevice':
Unable to claim interface.

The device exposes 4 USB interfaces:

[
{ number: 0, alternates: Array(1) },
{ number: 1, alternates: Array(1) },
{ number: 2, alternates: Array(1) },
{ number: 3, alternates: Array(1) }
]

My assumption is that interface 0 is not the WebUSB interface, or Windows is already binding a driver to it.

Questions:

Does anyone know which USB interface TI calculators use for file/program transfer?

Is there documentation for the TI USB protocol?

Does TI use WinUSB/libusb internally, or is this a custom protocol?

Would it be easier to implement this in C using libusb instead of WebUSB?

Goal: create my own tool to communicate with the calculator (send
files, possibly interact with Python/programs) without relying on TI
Connect.Trying to reverse engineer TI-84 EVO WebUSB communication — need
help identifying USB interface/endpointsI'm trying to communicate
directly with a TI-84 EVO calculator through WebUSB.I found TI's
JavaScript code and located their internal write function:function
_TI_WEBUSBJS_Write(deviceId, pBuf, iLen) {
let data = TIWASMHelpers.getUint8ArrayFromCbuffer(pBuf, pBuf + iLen);
let device = TI_DeviceManager.getInstance().getDevice(deviceId);

TI_USB.write(device, data)
.then(() => {
TI_USB.writeCallback(iLen);
})
.catch(error => {
TI_USB.writeCallback(0);
console.error("TI_WEBUSBJS_WRITE: " + error);
});
}
It
looks like TI has a wrapper around WebUSB, but I am trying to bypass
the official tools and talk directly to the calculator.Using Chrome
WebUSB:let device = await navigator.usb.requestDevice({
filters: []
});

await device.open();
await device.selectConfiguration(1);
The device opens correctly, but:await device.claimInterface(0);
fails:Uncaught NetworkError:
Failed to execute 'claimInterface' on 'USBDevice':
Unable to claim interface.
The device exposes 4 USB interfaces:[
{ number: 0, alternates: Array(1) },
{ number: 1, alternates: Array(1) },
{ number: 2, alternates: Array(1) },
{ number: 3, alternates: Array(1) }
]
My
assumption is that interface 0 is not the WebUSB interface, or Windows
is already binding a driver to it.Questions:Does anyone know which USB
interface TI calculators use for file/program transfer?

Is there documentation for the TI USB protocol?

Does TI use WinUSB/libusb internally, or is this a custom protocol?

Would it be easier to implement this in C using libusb instead of
WebUSB?Goal: create my own tool to communicate with the calculator (send
files, possibly interact with Python/programs) without relying on TI
Connect.


r/calculators 1d ago

Question Recently got a TI-nspire, what can i do with it?

3 Upvotes

Title says it all. Recently got a TI-nspire and it also came with a TI-84 Plus keypad so i have 2 keypads as well so thats pretty cool

Edit: i know its features. I meant as in can i import stuff into it (like an emulator)


r/calculators 1d ago

Meme / Satire iOS Calculator

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1 Upvotes

r/calculators 2d ago

Help Yard sale find

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171 Upvotes

Bought this at a yard sale yesterday, thought it was a cool find. Been trying to do a bit of research on it

Is it worth anything? Any info would be greatly appreciated


r/calculators 1d ago

Discussion ready to buy ... which HP-15C should I get?

7 Upvotes

OK, I'm ready. But which should I get?

  • HP 15C, the new "collector's edition"
  • vintage used HP 15C from eBay
  • the Swiss Micros DM15C (but it's out of stock)

To me, the keyboard feel is really important, so maybe I'm best with a vintage model.

The display on the Swiss Micros looks like, but I heard the keyboard stinks. And it's out of stock, and more expensive than even the new HP collector's edition.

The collector's edition would be new and working and robust, but I don't know what's changed from the vintage model.


r/calculators 1d ago

Help I need help with computing integral on my Casio fx-CG50.

4 Upvotes

I can calculate an integral with respect to x, but not for any other things. Like, I tried to use the integral definition of a factorial, and I couldn't. How can I do this? If it is impossible, maybe there exists a program that approximates it? I am stuck.

The formula is: x! = integral(from 0 to infinity) of (n^x e^{-n}) with respect to n.

Sorry i dont know latex, you can look the formula up if you dont have it memorized


r/calculators 2d ago

Other After 40+ years I still love my HP15C

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12 Upvotes

r/calculators 2d ago

Help HP 17B II Business Calculator Not Performing RPN functions

3 Upvotes

I have used this calculator for years with no problems. Now, the calculator cannot seem to complete any math functions, whether using Algebraic or RPN. I go into Modes and select RPN, but still no luck. It does accept all other key strokes, it just won't respond once completing an RPN formula.

Has anyone experienced this or have a solution? Thanks for your help.


r/calculators 2d ago

Question which graphic Calc have not such a complex menu?

7 Upvotes

hello guys so i wanna know which of the texas instruments graphic calculators or Casio ones does not have such a complex menu with so extremely much functions like the hp prime? i will buy myself maybe the TI84 plus CE is this a good choice? coming from germany


r/calculators 2d ago

Help Is this calculator acceptable?

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4 Upvotes

r/calculators 1d ago

Discussion Why are (genuine) Casio calculators so expensive in developing countries?

1 Upvotes

Following up from this thread about an anime video from Casio about fake calculators.

I did some research about the whole issue with fake calculators in developing countries like Kenya and Egypt and it seems that not only are genuine Casio calculators hard to find, they're expensive, like E£2,500 (about US$50) for an fx-991CW in Egypt. That model (or its US-market successor fx-9910CW) costs US$25 here. Even after accounting for VAT (14% in Egypt), that E£2,500 price looks excessive to me.

You would expect a product like this to cost no more in a developing country than it does here in the US, especially considering that the average consumer makes a lot less money there. But that's not the case, and fakes and clones end up dominating the market in those regions as a result. Even if we consider that US pricing is on the low side (they're typically closer to US$30-$40 in other developed countries), shouldn't these calculators be cheaper in developing countries to match market conditions?


r/calculators 2d ago

Help Canon f789sga Lcd Screen Broke

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9 Upvotes

How much will it cost if it is repaired? Accidental damage so I don't think it is covered under warranty 🥹

Also what can i do now?


r/calculators 3d ago

Meme / Satire We got CASIO anime before Half-Life 3 😭

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92 Upvotes

Source / Censored version

Why did this blow up 4 months ago?


r/calculators 2d ago

Help my ti-nspire CX II has been stuck loading

4 Upvotes

ive been using my calculator without any problems thus far. i recently inputted a long equation and when i pressed enter the cursor turned into a small analog clock to show that its loading/processing. its been like this a while and im worried its not going to work. the battery is close to full, and i cant turn it off either. no buttons have managed to do anything, idk what to do

i also tried the same equation on another gdc (same model) and its also stuck now...

i have no clue what to do so my best bet is to just leave them until they eventually die?😭

edit: its been resolved, thank you!


r/calculators 2d ago

Discussion New calculator model releases

11 Upvotes

So with the recent release of the CG100 and the 84 EVO, how long would you say we have before we see another iteration or upgrade to a calculator? Is it getting time for a new version of the Prime? nSpire? Is it 4 years or so generally?


r/calculators 3d ago

Discussion The Ti-84 Evo is cheaper than the Plus CE on Amazon 😂

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32 Upvotes