calculator not able to recall numbers

I don't know if anyone has noticed, but the calculator will only recall the LAST number entered, nothing else. I though i would get used to it before my exam, so i have been using white board and calculator every chance i get, but the calculator not recalling numbers is a huge problem, also you cannot copy n paste into it. every time you have to retype the numbers from scratch... leaving room for error... anyone else experiencing this? any advice?