I Europe we can choose between Casio, HP and TI. Problem is: Calculators are build for schools, not for using them in real life. Real Calculator: enter Number -> Press sqrt -> read result. Modern gameboy calculator: enter sqrt use cursor to go to number field -> enter number -> press equal -> read result. May be nice to learn how schoolbooks are written, but very inconvinient if you have to use the calculator for real
Depends on the models pretty much, I used scientific models like FX 4500P, the 880P, the CFX-9850GB PLUS during my education, and they had programming modes where that isn't the case.