A study designed to serve as an initial step in building a theory of computer literacy was conducted to provide new information concerning how humans think about calculators and to determine how individual differences in students' intuitions affect their understanding and use of the calculator. Thirty-three expert and 33 novice calculator users were asked to fill out questionnaires, and then to predict what number would be in the display of the calculator after a series of key presses for 88 math problems. Analytic techniques of cognitive psychology were applied to assess the performance of the subjects compared to the performance of the calculators, as well as subject performance in light of the type of calculator used, and the amount of previous experience with calculators. Results indicated that there were tremendous individual differences among users in their interpretations of the logic of the calculator's operating system. Future work is recommended to determine whether intuitions, once diagnosed, can be altered through instruction, and to determine whether people with certain intuitions can use their calculators more creatively or learn a new computer language more efficiently than people with other sets of intuition. Nineteen references are listed and supporting data are appended. (MER)