Fred Brooks predicted long ago that complex pieces of software would eventually reach the point of irreducible entropy, where any attempt to fix a bug would simply introduce a new one. Microsoft’s Windows 10 seems to be about there, and it’s now clear that Apple’s macOS 10.15 “Catalina” has also joined that elite group <https://www.theregister.co.uk/2020/05/27/apple_catalina_update/>: The first spin of Catalina, officially released in October 2019, was a mess. ... The biggest issue was that all kinds of apps simply stopped working. ... Peripherals like mice, keyboards and printers stopped working. Email went missing; iCloud backups failed; users were constantly harassed by login requests; updates didn’t update ... ... So came for the first update to its new system one week after the main launch which fixed some, but not all, of the issues. ... Version two came in December 2019 and fixed some of those issues, but not all. ... More bug fixes came with version three in January 2020, but the OS seemed to have finally stabilized; something that was then spectacularly undone with version .4. ... Then we had the “supplemental update” to version 10.15.4, which fixed some, but not all, of the problems – most significantly the problem with Finder and transferring large files. And, amazingly, appeared to undo the good work that had been done with website security and broke SSH for some users. But now, with version point-five this week, that problem appears to have been sorted and, of course, your battery might last longer too.