These "four-function" calculators only display the last number. It would be widely unexpected if doing x3 when all I see is a 2 would sometimes give 6 or some o

These "four-function" calculators only display the last number. It would be widely unexpected if doing x3 when all I see is a 2 would sometimes give 6 or some other value (e.g. the student next to me just passed a calculator with a value displayed, so I don't know if it had any previous instructions and no way to find out) The UX is pretty clear - it's ANS operator newNumber. That's it, if not somehow displayed, then it shouldn't have a more complicated model inside either. It can freely do "normal" math the moment they write out the whole expression tree, as the result of an expression is the one calculated by precedence rules. The result of a two-operand operation is not that, though.