Open charm production at HERA

Inclusive charm meson production cross sections in the deep inelastic scattering and photoproduction regimes are compared with QCD leading and next-to-leading order (NLO) calculations. The NLO predictions are significantly below the data in some parts of the measured kinematic range. Angular distributions of dijet events with charm show clear evidence for the existence of charm originating from the incoming photon. The charm fragmentation function is measured for the first time at HERA. Various fragmentation ratios and the fragmentation fractions of the low-lying charm hadrons are determined and compared to previous e+e− results.