In the meantime, did you ever own one of these devices (or something similar)?
When my brother passed in 2003, I inherited his Compaq iPaq (similar to this, although I don't think it was colour). I did try to get myself computer calendar literate, but there are two problems. Firstly I hate having something hitched onto my belt or in any of my pockets. Secondly it seemed to need charging every day or two, so I would have to develop some kind of discipline. It never took, nor has anything else. Despite the calendar on Outlook, a mobile phone (dumb, but still with a calendar/ appointment function), an iPad and a Microsoft Surface I still write everything down in a paper day-timer. Notwithstanding my work in this industry, apparently this dog can't change its spots.
I never had a Casio SF-7500 but I did have a Casio FX-850P Personal Computer. In fact I still have it some 25 years on and it still works.
Its an amazing device I used for storing names and phone numbers but best of all it came with the Basic language and 10 slots to store programs.
It got most of it's use during the construction of Sizewell B Nuclear Power station in Suffolk England, where I used its trig functions to calculate where I had installed stress measuring instrumentation within the cylindrical wall and dome of the reactor building. A surveyor would give me some measurements from known datum points and from that I could calculate the instruments radius, bearing and height within the building. Oh the memories of crawling around in steel work and concrete.
If it weren't for my smart phone, I would still be carrying this thing around. I don't think I will ever through it away even if it stops working.
@Max:But didn't you hear about the classic problem with the trig functions on Casio FX-850P Personal Computer ...LOL
Not that I recall but my calculations using the Casio were far more accurate than the surveyors, so much so he relied on me to produce the results for him on a few occasions, which I'm quite proud of being Math's isn't my strong point and it was his trade.
I use an HP95 (vintage 1990) pocket MS-DOS PC for writing on camping trips where I don't have access to chargers. The HP95 runs for more than a week from a pair of alkaline AA cells. It stores a standard FAT filesystem image on internal SRAM (C: drive) and on a removeable PCMCIA SRAM card (A: drive). MS-DOS, Lotus 1-2-3 spreadsheet, a simple text editor, and a few other programs are stored in masked ROM. The HP95 and the SRAM card both have coin cells for SRAM backup power.
I copy the files from the SRAM card onto a Linux box when I return home.