The Software Maintenance Spectrum

As the Air Force enters the 21st century, the software that runs our information systems continues to age and become harder to maintain. Organizations that maintain this legacy software are faced with the challenge of rising software maintenance costs. This paper presents a spectrum of software maintenance options that can be used to reduce the cost of maintenance. The software understanding and programmer unfamiliarity factors from the COCOMO II model are compared to graphically show the effect good software understandability can have on the cost of maintenance. The structure, application clarity, and self-descriptiveness of a software module affect its understandability. The cost of software maintenance is quantified by combining factors from the COCOMO II model and the Software Reengineering Assessment Handbook reengineering decision model that affect understandability.