  We review two lattice calculations involving charm hadrons: a determination
of the vector and scalar form factors of the semileptonic $D \to \pi \ell \nu$
decays, which are relevant for the extraction of the CKM matrix element $\lvert
V_{cd} \rvert$ from experimental data, and a calculation of the matrix elements
of four-fermion operators relevant to the description of the neutral D mixing
in the Standard Model and its extensions. Both analyses are based on the gauge
configurations produced by the European Twisted Mass Collaboration with $N_f =
2 + 1 + 1$ flavors of dynamical quarks. We simulated at three different values
of the lattice spacing and with pion masses as small as 210 MeV.
