Towards understanding code readability and its impact on design quality

Readability of code is commonly believed to impact the overall quality of software. Poor readability not only hinders developers from understanding what the code is doing but also can cause developers to make sub-optimal changes and introduce bugs. Developers also recognize this risk and state readability among their top information needs. Researchers have modeled readability scores. However, thus far, no one has investigated how readability evolves over time and how that impacts design quality of software. We perform a large scale study of 49 open source Java projects, spanning 8296 commits and 1766 files. We find that readability is high in open source projects and does not fluctuate over project’s lifetime unlike design quality of a project. Also readability has a non-significant correlation of 0.151 (Kendall’s τ ) with code smell count (indicator of design quality). Since current readability measure is unable to capture the increased difficulty in reading code due to the degraded design quality, our results hint towards the need of a better measurement and modeling of code readability.