All those younger programmers advocating “throwing that COBOL in the garbage and rewrite it from scratch,” don’t understand legacy systems. You should (almost) never rewrite from scratch, and (almost) never throw the legacy system away, it’s your institutional knowledge.

A legacy software system is years of undocumented corner cases, bug fixes, codified procedures, all wrapped inside software. If you start from scratch you’ll miss things. There is no guarantee that you’ll end up in a better situation, just a different one.

I’ve yet to speak to anyone that’s been involved with a project to reimplement a large legacy code base from scratch that has anything good to say about the idea. Document, improve the build system, modernise the infrastructure around it. Write tests. But don’t throw it away.

Just getting a modern build system on top of your legacy code base, getting it into revision control system, writing tests. That& #39;s years of work right there. Afterwards you& #39;ll be left with something that you can build and test easily. What& #39;s else did you want?