  The purpose of this paper is to study the properties of the solutions to the
biharmonic equations: $\Delta(\Delta f)=g$, where $g:$
$\overline{\mathbb{D}}\rightarrow\mathbb{C}$ is a continuous function and
$\overline{\mathbb{D}}$ denotes the closure of the unit disk $\mathbb{D}$ in
the complex plane $\mathbb{C}$. In fact, we establish the following properties
for those solutions: Firstly, we establish the Schwarz type lemma. Secondly, by
using the obtained results, we get a Landau type theorem. Thirdly, we discuss
their Lipschitz type property.
