Some limitations of computing with calculators and computers are described, with particular reference to typical computations which might be performed by senior secondary school students. Types of errors, the laws of number, and intermediate round-offs are each illustrated, with conclusions and implications. (MNS)

An overall schema of interpretation for programming instructors is given, so that the misconceptions students develop in programming can be determined more readily. Types of language-independent and -dependent bugs, how they can be identified, and how to help students overcome them are addressed. (MNS)

Computer software with graphic representations of functions can teach algebraic concepts, or can blur or obscure concepts of great importance. Making good use and bad use of visual imagery are each discussed. Then a general theory of interpretation of graphs is proposed, and a list of examples is presented. (MNS)