Apple has released Mac Os 10.15 Catalina, and it is the first to make the jump completely to 64 bit, abandoning the ability to run any 32 bit code. It is always recommended to wait a while to upgrade you system, or even better wait for 10.15.1 to work out some of the bugs. I am very interested in it though as I want to try out SideCar with my iPad Pro and Pencil.
Since there is no more 32 bit code many programs will not run, and you can tell which ones that will be in Mojave. Just to to your apple menu and About This Mac.
Then Select System Report:
Then go to Applications:
Then check the column that reads 64 bit and the applications that say no will certainly not work.
I have a lot of applications that will not work, but most are from old versions of Adobe that I still have installed.
Now I am certain to need some 32 bit application at some point in the future, and if you make the move to Catalina before taking some steps to ensure you can still run the applications you will never be able to.
My first step was to make a clone of my hard drive at Mojave for that I head over to Bombich and get the latest paid version of Carbon Copy Cloner. This is an amazing program I have used for years that will clone a hard drive and make a bootable copy. Now I have an iMac pro, so there are additional steps to be able to boot from an external drive thanks to the T2 security chip (you need to restart while holding down command and r and then change the startup security utility to allow external boot with at least Medium security instead of Full Security).
And to keep running 32 bit apps, since I own Parallels to be able to run Windows Applications on my Mac. Tidbits actually has a great article on how to do this using your Mojave Recovery Partition to create a clean install. Sure you will have to re-install the 32 bit apps to get them to run, but a nice clean install won’t take up the space that a full backup of my system would.
And finally it turns out I can’t upgrade to Catalina right now, as I run an external RAID using Softraid for my OWC Thunderbay. Now it will mount in Catalina, but will run slower and have no ability to recover hard drive that die or basically do anything with it in version 5.7.5. Now Softraid and OWC are an amazing company so they are working on it, but since Catalina is much more restrictive on running system extensions this one is going to be hard. It will first be available in 5.8, then in the new version 6 they are developing. I do hope it comes out soon.
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UPDATE!
Wow, so I got an e-mail from SoftRaid and OWC and they said that they should be releasing 5.8 within 24 hours with Catalina support! AWESOME!!!