CASIO fx-4000P scientific calculator from 1986

[vido]

The CASIO FX-4000P was a very good machine, you could keep 10 different programs into permanent memory, programs could call each other as subroutines, allowing to start in a given mode (typically the "normal" mode), make some calculation in a different one (SD, LR, even Base-N for example), display/pause or wait for user input to continue, use loops to fill indexed arrays (memory was 2kb, allotable between up to 550 steps/26 memories and 0 steps/lots of memories). Display was alpha only (no graphics) but there was a large character set. The language was not BASIC but a cleverly designed one, offering much of what to expect from a programming language.
There was a hack I stumbled on accidentally some day, allowing to have both 2000 steps and the max number of memory (simply said, the pointer to the end of the program area or the beginning of the memories area was set to an impossible value which gave "god mode" and unprotected access to the whole memory from either perspective). Needless to say, you could be overwriting programs with the content of some memories, which unlocked hidden functions and characters such as percentages, imaginary numbers and probably more. You could also very easily lose access to the already written programs, so this was to be handled with great caution.
I used this small beastie a lot at the time, and the only things I could gripe upon were that I would have loved to have a few kb more memory, and some I/O to store/retrieve programs and data.
The next models were a crippled version without a real programming language, just some "function definition" capability, or buffed up versions with more memory and display lines, but more massive already, which made them less convenient to keep in a shirt pocket.
Then the graphical calculators came, but they were too bulky and contained too much useless crapware for a comfortable use outside a classroom.

The FX-4000P was an exceptional calculator by CASIO. They could remake it the same size, with maybe a retrolit keyboard and 2-line screen allowing some pixel-level access, as well as the possiblity to read a keypress without waiting for a ENTER, some good memory amount and a SD Card reader, without sacrificing the convenience of a keyboard allowing ALPHA entry, and it would be great.

There is a CASIO fx-FD10 "pro" model which comes very close to this, but they committed the sin of getting rid of convenient access to Alpha entry mode, as well as most key 2nd functions, in favor of a confused menu system. Plus, it stinks of truck wheel rubber (Incredible !). Although I was quite disappointed when I discovered programming on the go is made very inconvenient, I won't resell that one, but I do hope there might be an update in the right direction some day.