You have performed a bad search. There are tons of content regarding disabling anonymous posting. I am too lazy to provide the links, if you are too lazy to search.
I would like to allow only limited viewing (possibly few topics or time limit) before it asks them to register.
It would be a custom paid solution.
But the generic allowance is for sure free and it is decribed even in Manual, not saying on forums in FAQ section etc. | 
