An obstacle to software reuse is the large number of major modifications that frequently have to be made as a consequence of dependencies within the reused software components. In this paper, common coupling is categorized and used as a measure of the dependencies between software components. We compared common coupling in three operating systems, Linux, FreeBSD, and Mach, and related it to the reuse effort of these systems. The measure is evaluated by studying the creation of two operating systems, MkLinux which is based on the reuse of Linux and Mach, and Darwin which is based on the reuse of FreeBSD and Mach. We conclude that the way that common coupling is implemented in Linux kernel induces large dependencies between software components, which required more effort in order to be reused to produce MkLinux, while the common coupling implemented in the Mach and FreeBSD kernels induces few dependencies between software components, which required less effort in order to be reused to produce Darwin.
Reuse; common coupling; kernel-based software; MkLinux; Darwin
