I use Mathematica 10 on MacBook Pro with macOS high Sierra 10.13.4 and when opening M10 got a message (see the screenshot) that M 10 is not optimised for Mac which means M10 is not running as 64 bit but as 32 bit app. M10 should be 64 bit app. How can I set M 10 as 64 bit app? soon no 32 bit apps will be able to run on coming version of OS.
As several people in the Stack Exchange article say, Mathematica 11.3 (and before) has a 64 bit kernel and a 32 bit front end. If you look at the builds that Stephen Wolfram uses in his “live CEO-ing”, you can see he uses version 12.0, which is 64 bit. How soon it will take for this to be ready is unknown, but it will almost certainly be this year.
My take is that it will be out before the next release of macOS is out,in the Fall.
Thanks for your input, it seems the front end of M10 is still 32 bit, and this is causing the problem. I ave not had any crashes yet and use M10 no problem but once apple releases its new version of OS very likely I and other won't be able to use m10 and other versions. Any idea when the update will be ready?
There should be no problem. The alert that macOS puts up is just a warning. None of the underlying APIs have changed. From what I can glean from Apple, 32 bit apps will still work under the next version of macOS, but with some possible issues.
In any case, I am pretty sure that Wolfram will have released Mathematica 12 before then. You might want to think about upgrading to version 12 when it comes out.