hp 20s
the input button is interesting because some binary operations like nCr require you to enter n, press input then enter r then press nCr. rather than, for example, enter n, press nCr, enter r, press =. most machine operate as the latter and indeed so does this for y^x. a comprehensive set of 2D statistical functions are on offer including linear regression. these use 9 of the 10 memories (0-9). programs in the memory can be assigned a label A-F which allow the routine to be executed from normal operation using xeq and then A-F. the literature claims support for solve, integrations, 3x3 matrices and complex numbers. aha! well, these features are actually implemented as rom built-in programs that can be loaded into the normal program memory using load then A-F. this, of course, means that the program memory is occupied and if you wished to write a program that uses any of these, you would have to squeeze it in to what is left. the built-in programs are modestly sized and do leave some space, especially since solve and integrate require a small program to define the function. note here, that there is no formula option like the 32sii and other more advanced models like the 48g. consequently, the ability of solve and integrate are somewhat simplified. solve uses a straightforward newton method with no refinements and integrate is just simpson's rule and there is no attempt to either use non-equal sample distances nor avoid calling the function at the limit points nor even track the error, unlike almost all other hp machines way back to the excellently designed 15c. but then its better like this than nothing, but dont expect quality quadrature. to be fair, it seems that all casio do is simpson's rule as well, eg fx-3900pv. |