  In this paper we consider the monoid $\DPC_n$ of all partial isometries of a
$n$-cycle graph $C_n$. We show that $\DPC_n$ is the submonoid of the monoid of
all oriented partial permutations on a $n$-chain whose elements are precisely
all restrictions of the dihedral group of order $2n$. Our main aim is to
exhibit a presentation of $\DPC_n$. We also describe Green's relations of
$\DPC_n$ and calculate its cardinal and rank.
