This paper reports on an empirical study of the cognitive processes involved in program
comprehension. Verbal protocols were gathered from professional programmers as they
were engaged in a program-understanding task. Based on analysis of these protocols,
several types of interesting cognitive events were identified. These include asking questions
and conjecturing facts about the code. We describe these event types and use them to
derive a computational model of the programmers' mental processes.

Changes in an organization's internal and external environment impose numerous demands
on management information systems (MIS). Since few MIS can be designed to fully
anticipate all change, system portfolios frequently tend to become heavily weighted with
older systems needing maintenance and revision. To maintain cost effectiveness,
encourage system reuse, and ensure that the new system's behavior will differ from that of
the old one only as intended, the former's functional design must be recovered (preferably …