It is known that the group $\ C(\Bbb R)$$C(\Bbb R)$ has at most two connected components, and the connected component of the identity is isomorphic to U(1)$U(1)$ as a topological group (trivially) and $\ C(\Bbb Q)$$C(\Bbb Q)$ is isomorphic to $\Bbb Z^r\times E(\Bbb Q)$, where all possible $\ E(\Bbb Q)$$E(\Bbb Q)$ are known.
Are there similar results for other fields? I am especially interested in the case K is a number field, or the p-adic numbers (both $\Bbb Z_p$ and $\Bbb Q_p$)