Software Reliability Techniques for Real-World Applications

2Understanding Defects

To prevent and control software defects, we need to understand them. This chapter explains the nature of software defects, including where they enter into the system, what effects they can have, how to detect them, and what causes them.

To reduce the number and impact of defects in our software, it is important to understand the nature of errors and defects. Almost any error on a project can affect the reliability of the software. Anything that makes it more difficult for project personnel to perform their tasks can negatively impact reliability, even if it does not directly result in placing a defect in the software code. A frustrated, angry, or confused programmer is more likely to make an error resulting in a software defect than a motivated, generally happy, and well-informed programmer. A poor work environment and a lack of good software development tools are examples of defect precursors. Defect precursors do not directly cause a software defect, but they make defects more likely and so are considerations for software reliability. Projects that produce high-quality software tend to be well-run projects. Not all errors or defect precursors result in defects, but reducing errors and precursors reduces the likelihood of defects. Similarly, not all defects produce software faults, and not all software faults result in software failures, but again, reducing them improves our chances of reliable software.

As we want to produce reliable software, our understanding ...