Attempted to provide a detailed look at the representations of expert and novice problem solvers by characterizing some of the properties of the abstract and concrete representations formed during the comprehension of computer programs. 36 Ss formed 2 groups: 18 undergraduates who had completed an introductory computer programming course formed the novice group and 18 teaching fellows of the same course formed the expert group. The data suggest that, in the absence of an experimentally provided set, experts form abstract representations (defined here as what a program does), whereas novices form concrete representations (defined here as how a program functions). The data also suggest that appropriate sets can aid each group to form the representation not natural to them; however, these representations are not as stable as the preferred ones. The generality of the findings and the utility of the experts' representation of a task are discussed both in relation to computer programming and to problem solving in other domains. (22 ref) (PsycINFO Database Record (c) 2016 APA, all rights reserved)