If you restart windows durring an update then there is a large chance you will have to reinstall.
When you say you "updated" windows what did you do exactly.
While 12 hours is certainly excessive if it mass caught up on years worth of updates it takes some time, even more so if you have a very slow computer/internet connection.
0% for 12 hours = no progress and the only choice is to restart the PC and see what happens, probably will resume the update
Most likley yes will have to restart it, but still best to know the circumstances and also make OP aware that any restart mid-update is a good potential for needing to completely reinstall windows.
It is a hope for the best but come to terms with the reinsall sort of thing.
So I installed Windows on a new SSD. I was just installing programs on the computer. When I was going to shut down the computer I seen that Windows wanted to update then restart.
After that it took me to the screen installing 0 out of 212 this part was moving rather quickly before I left my house. Came home and seen the 0% updating your system figured it would take a little bit. left it over night and still same screen. I have already tried to restart the computer.