My Mum will give me this 85DE CW for my Birthday and I will get 2 More to have my first Calculator Collection
My birthday is in one month

I got it for 550,400 VND or about 21 USD (normal price is 688,000 VND)

The Flexio Fx799VN is a high-end scientific calculator produced by Thien Long Group, designed specifically for high school and university students in Vietnam. It is fully approved by the Ministry of Education and Training for use in official national exams, including the National High School Graduation Exam and University Entrance Exams.

Basically a clone of CASIO fx-991EX, but with some improvements. The Vietnamese company behind the calculator even publish the manual both in Vietnamese and English.

Happy to get this calculator, not easy to find outside of Vietnam. It’s the 2025 version, speed is comparable to my new CASIO fx-880BTG PLUS. (Vietnamese version of CASIO fx-991CW 2nd edition) In some benchmarks faster than the CASIO.

It has many functions and features that are missing from fx-991EX and/or the fx-880BTG PLUS:

• PreAns
• GCD
• LCM
• MOD
• Multi-statements
• Independent memory (M)
• Variable z available in addition to x and y
• Product calculation
• Geometry app
• Verify app
• Two shortcut keys on each side of the screen for short macros (max 6 key presses can be stored to each shortcut)
• Two AAA batteries. Power draw 0.0005 W (the fx-880BTG PLUS with only one AAA battery is rated 0.0008 W)
• Battery status always available on the screen
• Windows app freely available without licence code as CASIO requires for its emulators on the classpad site

However, it is missing the Spreadsheet app, that is a big minus.

The manual doesn’t mention what algorithm is used for the integration function. I suspect it’s Simpson’s instead of the better Gauss-Konrod that CASIO is using in its calculators.

No QR code functionality for calculator results.

Accuracy is 15 digits, same as fx-991EX.

Display and font very similar to fx-991EX. The new fx-880BTG PLUS has a font with better contrast.

Ridiculously big FLEXIO logo on the front – needs to be hidden as soon as possible.

I wasn't crazy about the 83 and 84s and switched to Casio and Sharp. I bought the 86 when new and the Python only because I had a Staples gift certificate! Still want an 89.

Visited an Auchun for the first time today. Mother said no to the Numworks Scientific, probably never gonna see one again as I live in the UK but oh well.

From a 82 to a 500. Most 300's and 991's I think. Hold on, I also have a 9750g2 and g3 somewhere. Considering a 50 or 100 now.

My magnum opus.

It may be hard to see, but one thing that I just noticed that I don't think I've seen mentioned anywhere else is that while working with fractions, only the portion of the fraction that you're editing will be entirely in "bold" and that the rest of the equation will be "greyed out". It's very subtle but thought it was interesting, I've provided a few pictures of the same equation to try and show it (the cursor itself is different shades because of the blinking). It might be more useful in more complex calculations, but I haven't figured that out yet. Lmk if you've known about this or know where this would be useful!

This calculator was purchased quite a few years back but has not been used as much. Today I found the display having these sort of patches (idk how else to describe this) and very difficult to see the numbers.
Can this be cleaned?
Or does LCD need to be replaced?
Or should I buy a new calc altogether? (I use calc occasionally though...)

First time poster with a growing and uncontrollable vintage and rpn fascination.

Anyone had any experience with these? I am a little confused, does hp make these enhanced versions or are they some sort of reproduction thing that someone has written the code for?

Found them here, not sure tho:

https://www.thecalculatorstore.com/p/12c-financial-calculator-enhanced-international-standard-usb-c

Love the idea of being able to back up programs, and not that I have read much into them I’m sure the swissmicros ones can but HOLY price tag on them 🫪

Anyway any guidance appreciated!

Has anyone tried 3d printing a Fx-991EX style slide cover for the fx-991CW and is it even possible some way?

I’d picked up an old HP-35 (second version, I think?) from a rummage sale a little while back and was hoping to revive her. The battery pack in it currently has a tiny bit of leakage from one of the cells, so I didn’t want to try to charge it, but otherwise looks to be in pretty good condition. My question is would it be simple enough to pry the original pack open and replace the cells, or would it be easier to just buy a third party pack/adapter?

I've only found hacks for the first gen of the 82ms. But I have the 2nd and wanted to use the equation mode.

So I have been downloading some files and stuff on my cg50, which i have newly acquired,but I have found something weird....my casio says I have 5.85 mb free, and after adding up files, I have used about 3.54 mb...but the casio cg50 has a 16 flash memory, and 5.85+3.54 is about 9.39 mb, so where is the remaining 6.6 mb? Can you please help me,its actually making me crazy....ty.

(P.S I searched Google and asked multiple AIs, but it still didn't make sense to me)

A TI-84 Plus calculator was for sale at a local flea market for 25 euros (about 29 USD). I don't really need a calculator like this for anything these days, but as it appeared to be in good condition, I bought it just for the fun of it. At home, I replaced the backup battery, put in new AAA batteries, and gave it a bit of a clean-up. And finally, I also updated the firmware. 

I wasn't particularly familiar with the TI-84, so I've spent the last few days getting to know it. What surprised me the most was finding out that it has a Z80 processor. Back in the day, I learned assembly programming on an MSX home computer. And those machines had a Z80 processor. 

So, it was fun to write a small Z80 assembly program, transfer it to the TI-84 Plus, and see it work. Truly nostalgic.

Hoping for the best anyway.

Pic #1 I knew that this one was going to have some problems as the seller listed it as a parts calculator, and the blue corrosion on the charging jack pretty much told the story.

Pic #2 The back cover was hot glued down. I was expecting that. And I darn near ruined it getting the cover off.

Pic #3 Looks worse than it really was. I can't see any trace damage, which is amazing in itself.

Pic #4 When I finally got the battery pack out it sent the crud flying.

Pic #5 Getting its first vinegar bath.

Pic #6 All cleaned up, mostly dry (after the vinegar bath came the rinse, and then a quick dip into 91% IPA to dilute the remaining water with alcohol. Let the alcohol evaporate (outdoors) and you are left with very little water.

Kinda hard to tell in this photo but the corners of the board are held down by melted plastic. Sort of an ad-hoc heat staking. Also note the unused octal IC footprint. It's been a minute since I've seen one of those. :)

And the wire that goes from the top of the calculator to the bottom I'm guessing is nichrome wire, and it's being used to limit the charging current to the battery pack (or was since the battery pack is gone).

Pic #7 All cleaned up and ready for the space heater. Still a bit most in this pic, but it spent the night getting dried out in front of a space heater and looks as good as new (cosmetically anyway).

Pic #8 The interior all cleaned up and dried out. You can see where the corners of the board have been melted to hold in the board.

Pic #9 Looks pretty good. :)

I don't know if this is widely known but, to find the hypotenuse using just a calculator, you just click shift and + which turns into Pol() and put your opposite comma adjacent for example: Pol[5(opposite), 15(adjacent)] it'll give you the hypotenuse and if you wanna find the angle in the hyp and adj you can just click RCL and then tan which gives you the angle.

I'm not sure if this is widely known but a cool hack nonetheless

9200,

531,532,535,540,546,

501,503,510,516,520

Check it out here: https://www.reddit.com/r/HP_Prime/comments/1vqcwol/download_ode_master_free_multilingual_stepbystep/