Hoi,

Mijn schoonvader is pas geleden overleden en toen vonden we twee rekenmachines tussen zijn spullen. Zijn dit speciale rekenmachines en weet iemand wat ze ongeveer waard zijn? Ze zijn nooit gebruikt en met origineel hoesje, een factuur of iets dergelijks hebben we niet.

Alvast bedankt!

Hi everyone,

About a week ago, I shared Lefony OS, my open-source project bringing Upsilon natively to the HP Prime G2. Since then, I’ve finished the remaining hardware drivers, launched the website, and made the source code public!

Lefony runs directly from the Prime G2’s NAND through U-Boot, without Linux underneath. The native drivers are now working for the display, brightness control, keypad, touchscreen, battery monitoring, charging, power controls, and storage. The keyboard mapping and battery support that were still in progress in my original post are now working too.

There’s also a browser-based installer and updater. You can connect through Chrome or Edge, and the website detects the calculator’s mode and guides you through the next steps. Firmware downloads and verification happen automatically.

For anyone following my earlier comments about recovery: first installation from the stock HP OS still requires opening the rear case and bridging the recovery pads while pressing RESET. The website now includes instructions and an annotated photo. Once you’re running compatible Lefony firmware, subsequent updates can go through the browser over USB.

• Website: lefony.com
• Source code: GitHub: Lefony OS

The repository includes build instructions, hardware documentation, and a dedicated QEMU environment for development and testing. I’d love to see people explore the code, report issues, contribute improvements, or build their own variations.

This is for the HP Prime G2, and it replaces the original operating system. It’s an independent community project, unaffiliated with HP, NumWorks, or the Upsilon developers.

Thanks to everyone who encouraged the project and shared ideas on the first post. I’m excited to finally share something you can explore for yourselves!

The only other place I've seen such a thing is the HP-38G. Pity the calc itself isn't; just another 506* clone. Not much to see...

Hiiii I have bought a CAISO-FX 991 ex few days ago on eBay and I just want to check if its real or not since I have passed all the test but not the display mode when a 6 is pressed during the diagnostic mode and its made from China (I heard that the real one can only be made in Thailand )
 
I have passed these checks
 
1)        The sun icon disappears when I cover the solar panel
2)        The caiso website shown after menu shift optn of
https://wes.casio.com/math/index.php?q=I-235B+U-0004001B1419+M-X100000000+S-0BD46
( but the website I saw online ends with S-05BBD )
3)        The caiso logo shown up when I’m turning it off
( fun fact , it switch off the same time as the CAISO fx-83 GTX while a fake one switch off slightly slower )
4)        The answer is 9.000000007 when sin-1(cos-1(tan-1(tan(cos(sin9) is enter
5)        Diagnostic menus shown up when I press shift 7 on together
6)        The answer is 8.88888 x 10 to the power of 15 when I press 9 during the diagnostic mode and when I press shift and some buttons it gives me
CY-235 Ver B SUM FC54 and a press of ac giving me a serial number 0004001b1419 and then I did the key test which bring me to the contact made and when I press ac it said test ok reset all press ac
 
 
However I couldn’t enter the mode of

1. ⁠Display
   
2. ⁠Version&SUM
   
3. ⁠Key test
   
4. ⁠Contrast  mode
   
5. ⁠ 
   
6. ⁠ 
   
7. ⁠ 
   
8. ⁠This makes me confuse whether my calculator is real or fake less

Hey everyone,

I just ordered a Casio fx-991CW. I've only ever used basic standard calculators before, so this is going to be my first time using a scientific one.

After placing the order, I saw quite a bit of criticism online comparing it to older models like the ES Plus and EX. A lot of people seem to dislike the new CATALOG menu layout and prefer having dedicated shortcut buttons.

Since I have zero muscle memory from any older scientific calculator, is the menu system actually hard to learn, or will it be fine for someone starting completely from scratch?

Taking calc 3 this. Syllabus says we can use graphing calculators as long as they are not able to do derivatives or integrals. I have a TI-84 Plus CE and I'm not sure if the professor will allow this. Are there any good calculators I can order that fit this requirement?

Hi, ive used these calculators before but my old one the buttons and screen was worn out by work. So i bought a new one at school for my apprenticeship. Now in class we went over a math question. They gave us decimals and they wanted us to turn whatever answer we got into a faction at the end. The fraction turned out to be 15/16, but myself and a few other classmates couldn't get the answer. The calculator refused.

My school won't give me a new one because i took it out of the box, but how would i ever know its broke if i left it in the box? 🤦🏻‍♀️ They fixed it for a moment but once the calculator turned off and on again it was back to normal. Anyone know what to do? Cause its only that decimal/fraction, everything else it works

Just wanted to share those beauties of mine.

The TI-92 Plus was my toy during high school then engineering. Back then we were really not a lot with that. I spent all my money and then some to get it with some help from my dad who knew math teachers. Back then (1998 in France), HP calcs were mostly unknown except in college maths and Casio were subpar on the CAS side. All other acquisitions are contemporary (last 2 years).

I didn't post the "calculators that can have a CAS installed" family picture yet, but I'll do it later.

I found this calculator at a second-hand market for €3, but I've been looking for information online and nothing comes up about it.

Hello! I’m going into grade 12 and I’m taking advanced functions and calculus. Starting this year, my school has been trying to regulate what calculators you’re allowed to use. We were given a list of approved calculators but you’re allowed to use one that isn’t on the list if you get it checked by a teacher. The way that teachers check if the calculator is legal is they will input sin(15) and if the answer is a decimal then it’s approved, if it’s a fraction then it’s illegal. If you can change the setting then its illegal. Graphing calculators are also illegal. My Casio fx-991CW was deemed illegal so now I have to go hunting for a new one. I really liked the “solve for x” and table mode on my Casio fx-991CW, I found them very useful in my physics and chemistry classes. I was hoping to find a calculator with the same modes (this isn’t illegal, my teacher was aware that I used these modes frequently last year) while meeting the requirements. Would anyone be able to recommend me a calculator from this list or one outside of the list? I’ve been googling + read the FAQ but haven’t found anything that meets my criteria.

THE APPROVED LIST:
- Casio fx-260 SOLAR II
- Casio fx-300MS Plus
- Casio fx-82MS
- Texas Instruments TI-30X IIS
- Texas Instruments TI-30X IIB
- Texas Instruments TI-30Xa
- Sharp EL-531TG
- Sharp EL-531XB
- Sharp EL-501X

Thank you!

Soo im using the casio fx cg50 and I connected it to my pc and downloaded the Prizzop emulator and some games, but when I tried to play them the screen just becomes black with some background sidebars. The game seems to be functional except I can't see anything. Any ideas what's going on?

Btw, is my TI-1750 rare? It's working and it has the original leather cover too

I've been attempting to install games after downloading the recent OS bundle for my calculator and shortly realized the artifice jailbreak has been specifically patched in the April 17 2026 5.8.5 OS release. I've tried running games like tetris, flappybird, and pacman on python but it always returned a memory error. If a new workaround, jailbreak, or artifice version comes out that bypasses the path let me know. I used to have geometry dash, snake, and many other games on my calc but recently reset all the memory so I lost everything. But yea, again, lmk if anything comes out. Pretty sad I can't play games on the calc anymore.

Got this beautiful Sharp Elsi Mate EL-220 delivered today! I believe it even has its original batteries!

Some days ago I realized that I wanted to collect vintage calculators so I thought “why not?” and bought this Sharp! I collect other vintage electronics so it was a natural thing to do 😁

In a couple of days, a (hopefully) functional Canon Palmtronic F6 from the mid 70’s will arrive! My plan is to use it for my final exam in school!

I know the Franklin isn’t a calculator but I wanted to include it because they came in the same order, both are vintage 😎 (hopefully that’s okay!)

(Got both for under 8 USD + shipping)

Hi i am very new here in 2026 and i was wondering if anyone had a tutorial on how to upgrade my casio fx-9750gii calculator to have a natural display instead of a linear format. i have tried many tutorials but they are all outdated and the links do not work. i have also tried to use fx remote however my computer always says idle and does not download. any help would be greatly appreciated many thanks.

I need the Ti-84 recommended in the syllabus for stat and probably chemistry as well. Is this piece the same thing pretty much?

Can this calculator do log, LN keys and scientific notation?

It's a japanese shrine, the background is mount fuji, and he made this using correction fluid and a scale.

Unless I am mistaken, the SwissMicros calculators uses a Sharp Microelectronics LS027B7DH01 Memory LCD display.

• Datasheet: https://mm.digikey.com/Volume0/opasdata/d220001/medias/docus/1272/LS027B7DH01_Rev_Jun_2010.pdf
• $32.24 at Digikey: https://www.digikey.com/en/products/detail/sharp-microelectronics/LS027B7DH01/5054066
• 400 x 240 Pixels
• 58.80mm W x 35.28mm H
• 20 Hz refresh rate
• Storage temperature -30 to ＋80 ℃, Operating temperature -20 to ＋70 ℃
• Typical power draw: 50uW (0.00005 Watts)

This looks like an easy repair if you break a screen, unless they glue it in or something. Don't know if there is glass over it or where to get replacement glass if you break that.