AbstractAlthough substantial variety exists among small programming environments, common points‐of‐choice in their design suggest the following structural characterization: real or virtual hardware; message‐passing or procedure‐calling; static or dynamic binding; horizontal or vertical organization; abstract or concrete structures; fixed or extensible language. Often these dimensions must support a very focused programming idiom, which combined with other requirements such as portability or performance, establishes structural dependencies, precludes features and forces exceptions. The characterization provides a rough framework that is useful in evaluating programming envir