The nonleptonic two body decays of the $D$ and $D_s$ mesons represent a key subject to study possible effects of CP violation. The attention for these decay modes was triggered four years ago by the results of measurements of the difference between CP asymmetries in charged $KK$ and $\pi\pi$ final state, $\Delta a_{\rm CP}$. Although the measured
$\Delta a_{\rm CP}$ is now compatible with zero the nonleptonic decays of charmed mesons into a pair of light mesons is an interesting subject for many reasons. Here we
discuss phenomenological models to study the decays into two pseudoscalar mesons.