Refining existing theories of program comprehension during maintenance for concurrent software

While the sources of complexity in the initial design and verification of multi-threaded software systems are well-documented, less is known of the issues specific to the maintenance of these systems. The literature contains a number of observational studies of programmers performing maintenance, conducted in the context of sequential software and designed to investigate the factors and behaviors that lead to success. To help fill the gap in knowledge in the area of concurrent software maintenance, we conducted a study that refines the findings of two prior studies, those of Littman et al. and of Vessey, to address issues and obstacles that arise in the understanding of concurrent software. We validated these refinements by observing programmers performing corrective maintenance on a small but complex multi-threaded server program.