Casio calculators also have a seperate exam mode where they clear all memory and do not allow the user to get to advanced function such as programming or derivative guessers. On the newer models a special led light on the top would indicate if the calculator is in this mode. You can disable this mode only by plugging in a usb cable and connect it to a pc or other calculator.

On all dutch state exams they simply checked this light on my calculator. But a friend of mine showed me already that there exsics special firmware that can fake this light so yhea 100% security will never exist.