All too few people in the software development seem to have read (or even heard about) Howard Baetjer Jr.’s Software as Capital book. Obviously, for a book written back in 1998, some of the ideas in the book will seem outdated, but the concepts are alive and well.
We often talk about legacy software as if it is a drag on a business. But for many software companies, the legacy software is the main source of revenue for the organization. Software is effectively embodied design decisions that have been written down over multiple years into the source code. These documented decisions are valuable, and are effectively the capital resources of the organization.
This is one of the reasons that rewrites are so difficult. The knowledge embedded in the existing code can be difficult to extract by the developers doing the rewrite. If an organization is good at looking after the existing source code – maintaining their capital assets – then extracting that knowledge is easier.