Effective Size: An Example of Use from Legacy Systems

✍ Scribed by CHAPIN, NED; LAU, TONY S.

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 874 KB
• Volume: 8
• Category: Article
• ISSN: 1040-550X
• DOI: 10.1002/(sici)1096-908x(199603)8:2<101::aid-smr125>3.0.co;2-3

✦ Synopsis

As part of a quality assurance effort directed at legacy systems, we examined a high-cost hardto-maintain COBOL program. Although written originally in 1968, it had been restructured in 1985 and has been well maintained since. It has the reputation of being 100 per cent wellstructured in the software engineering sense, of being very reliable in execution in overnight batch, but of being expensive and difficult t~ maintain. Our examination covered cyclomatic complexity, iteration, language use, IF-nesting depth, program structure and hierarchical depth. Our most significant finding was the effective size of this nearly 600 module program. Instead of having an effective size (exampled in the paper) of nearly 1.0, its effective size exceeded 13000! This extreme effective size made the program much harder to understand when in maintenance than the program's source-list size and other characteristics would suggest. Our findings included identifying the cause of the extreme effective size. From our experience with this program, we learned seven lessons applicable to improving the maintenance of legacy systems.