Are PA and ZFC examples of logical systems? Wikipedia says 

A logical system or, for short, logic, is a formal system together with a form of semantics, usually in the form of model-theoretic interpretation, which assigns truth values to sentences of the formal language.

When we talk about PA or ZFC, are these logical systems, or are they merely formal systems?

When I talk about a logical system in the way that 

A logical system or, for short, logic, is a formal system together with a form of semantics, usually in the form of model-theoretic interpretation

I understand that a logic $\mathcal{L}$ is a pair $(L,\models)$, where $L$ is a function, and the domain of $L$ is the  class of all the signatures. But the signature of $ZFC$ has just a member, $\in$. So, there is no sense in talk in the $ZFC$ as a logic. 
