In this paper, the authors discover the model of code readability and study its relation to software quality. It is a new advance to measuring the complexity of software systems. Software industry uses software metrics to measure the complexity of software systems for software cost estimation, software development control, software assurance, software testing, and software maintenance. With data collected from open source project, they derive associations between a simple set of local code features and human notions of readability. They construct an automated readability measure and show that it can be 80% effective, and better than a human on average, at predicting readability judgments. Furthermore, they show that this metric correlates strongly with many measures of software quality.