Error search and correction are major contributors to software development cost, yet typically uncover only a small fraction of software errors. Postrelease errors, i.e., those that are only observed after a system is released, threaten a variety of potential failures and consequences, each with low individual probability of occurrence. The combined effect of postrelease errors can and often does result in a significant rate of occurrence of these potential failures, with unpredictable consequences and severity. One particular source of postrelease errors that has received extensive publicity is the year 2000, or Y2K, error. The modeling in this research report suggests that testing probably needs to be conducted over more than half of the useful life of a system in order to discover even one-third of the total errors in the system. It suggests that short product lifecycles, lifetime testing, and effective feedback loops for error reporting are necessary to assure reliable software.
As corporate management attempts to extract more end user benefit from information systems department expenditures, interest has grown toward the use of information systems auditing to assure software quality. This research shows that information systems departments are motivated by end users to provide lower quality systems than they would if allowed to pursue their own objectives. The research continues by demonstrating that auditing cannot a priori be assumed to raise the quality of corporate information systems. In fact, auditing tends to establish objectives that lower software quality. It demonstrates that audits are most beneficial in managing unsophisticated information systems departments in which end users are currently dissatisfied with their level of support. Augmenting the systems development process via technologies such as computer aided software engineering and prototyping may more consistently and effectively improve quality than does auditing. Recent developments among the large audit firms indicate that they recognize the importance of new software development technology, and are restructuring their businesses accordingly.