Amusingly, the interface Marco points out as not having any real-world equivalent is actually fairly close (barring lack of keypad) to what my Casio scientific

Amusingly, the interface Marco points out as not having any real-world equivalent is actually fairly close (barring lack of keypad) to what my Casio scientific calculator does - calculation history, variable references, editing and all. The inability of most bundled calculator applications to live up to a £15 pocket calculator has been a source of frustration for me for quite some time - it's not that the calculators fail by replicating a real-world object; it's that they fail by not replicating the right one :)