A Comparative Study of Maintainability Index of Open Source Software

The development of Open Source Software (OSS) is fundamentally different from the proprietary software. In the OSS development scenario a single developer or group of developers writes the source code for the first version of the software and make it freely available over the internet. Then other developers are invited to contribute to the existing code for its next release. Making the source code of the software available on the internet allows developers around the world to contribute code, add new functionality, improvement of the existing source code and submitting bug fixes to the current release. In such a software development scenario the maintenance of the open source software is a perpetual task. Developing an OSS system implies a series of frequent maintenance efforts for debugging existing functionality and adding new functionality to the software system. The process of making the modifications to software systems after their first release is known as maintenance process. The term maintainability is closely related to the software maintenance because maintainability means the easiness to perform maintenance of the system. The most widely used software metric to quantify the maintainability is known as Maintainability Index (MI). In this study the MI of four most popular OSS namely Apache, Mozilla Firefox, MySql and FileZilla for fifty successive releases was empirically investigated. The MI in terms of software metrics namely Lines of Code (LOC), Cyclomatic Complexity (CC), and Halstead Volume (V) was computed for all the fifty successive versions of four OSS. The software metrics were calculated using Resource Standard Metrics (RSM) tool and Crystal Flow tool. It was observed from the results that the MI value was the highest in case of Mozilla Firefox and was the lowest in the case of Apache OSS.