>> I have to admit that I don’t fully understand why COBOL is so difficult to replace. If the systems are so vital surely there is a detailed specification and

>> I have to admit that I don’t fully understand why COBOL is so difficult to replace. If the systems are so vital surely there is a detailed specification and writing in an easier to maintain language would repay the effort? > Realistically If there were detailed specifications, they were hard copy print-outs from the 80s that are probably no longer readable, and undoubtedly were thrown away in the intervening decades. Or not kept up to date. My employer has some mainframe systems, and when they were built they had technical writers and created pretty good documentation, organized in binders. For the last two decades, at least, these systems have been "legacy" and the company stopped employing technical writers. During that time, they were still pretty critical, but I'm pretty sure no one kept that documentation up to date with whatever changes were made. Also, about a year before the pandemic, we had building reorganization, and a lot of those binders were thrown out during the move. They were kept on several large, neglected shared bookshelves, and I think anything anyone didn't specifically claim was discarded by facilities. The thing with legacy systems is they can be vital, but they also can be neglected. The gamble most businesses seem to take is: "as long as it works, starve it and hope it doesn't blow up on my watch."