Firstly my Mac Mini, a 2012 model, doesn't get the newest release of the MacOS operating system. What's that all about, Apple? I mean, it's only eight years old! Don't get me wrong. The thing is working fine. It did have a little blip a few months ago when the bluetooth connection stopped working, but I took it apart and put it back together and it's been fine since. But I guess I'm going to have to see how important it is to have that new operating system and if I really need it, I'll have to find a new Mac. It's a pain to think of changing something that's working well, but we do it with cars, don't we. We anticipate problems to come.... Meanwhile my laptop, a 2015 MacBook Pro, does get the new software, so I did the upgrade yesterday morning. The disk's a bit full so I uninstalled some of my big programs, upgraded the software, then installed them again. Now it's running fine again. It did have a problem - the anti-reflection coating