With regard to the issue raised by Pang-Chieh Chou:
For a number of years it has been my policy not to permit the use of calculators
during exams. (This is for the calculus-based introductory course.) I prefer to
give non-numerical exams for two reasons:
(i) They are easier to grade. When students plug in numbers at the beginning of
a problem (as is their wont), it rapidly becomes difficult to follow where
they're going. If they work with a small number of symbols, it's easier to keep
track of what the student is doing.
(ii) I don't have to worry about students whose calculator batteries fail in
mid-exam. (That was certainly one advantage of slide rules!)
My attitude is that numbers are something that gets plugged in at the end of a
problem, not at the beginning. By leaving the numbers off the exams, I am
essentially making the problems shorter!