casio fx-3500p

a very fine model predating all the "super fx" solar types. this is one of the old wallet style units with plastic keys (not rubber). a good set of scientific functions, fractions, 2d stats, linear regression, numerical integration, programmable and a nice 10+2 digit lcd display.

the keyboard layout is quite good apart from square root on a shift key and the mode button on the top right looks a bit out of place.

programming is limited to 38 steps of blind program together with the blind jumps x>0 and x<=m which can only jump back to the start. it is clear that the program feature is designed for short formulae (p1 or p2), either for evaluation or for use in numerical integration.

the feature set is the same (except for hyp) as the fx-180p. they calculate the same results and are essentially the same model in different packages.

few old casios offer built-in numerical integration and it is always internally implemented by simpson's rule. a more recent model to do this is the fx-3900pv (which is also a bit faster).