TERAD91: A Program package for the calculation of the cross sections of deep inelastic NC and CC scattering at HERA

We present a brief description of the recently developed Fortran code TERAD91 for semi-analytical calculations of the double differential cross sections of NC and CC deep inelastic electron-proton scattering and of some related observables. The code is mainly intended for the calculations at HERA or other ep-colliders but may be also used for similar processes like muon-proton scattering in fixed-target experiments.