einSTein   
by Lis Schmitz   

einSTein is a 32-bit
all-purpose programmable calculator that also accepts expressions and functions. It
includes all mathematical, trigonometric, and financial functions, as well
as calendar computing. Its RPN function lets you compute the interest rate
of any cash transaction. You can calculate the real interest rate of loans,
investments, saving accounts, leasing, and more and even convert numbers
between 120 different measures, grouped in 12 categories. einSTein also lets
you calculate all the values of a triangle (sides, angles, height, area) if
you know three of the values, get the solution of equations up to the sixteenth
gradient, and do complex and vectorial calculations. With tape functionality, reminder and calendar. Select from an English,
Italian, Spanish, or German interface.