Radiative corrections to DIS

Early deep inelastic scattering (DIS) experiments at SLAC discovered partons, identified them as quarks and gluons, and restricted the set of the candidate theories for strong interactions to those exhibiting the asymptotic freedom property. The next generation DIS experiments at FNAL and CERN confirmed the predictions of QCD for the size of the scaling violation effects in the nucleon structure functions. The QCD fits to their data resulted in determining the momentum distributions of the point-like constituents of nucleons. Interpretation of data coming from all these experiments and, in the case of the SLAC experiments, even an elaboration of the running strategies, would not have been possible without a precise understanding of the electromagnetic radiative corrections. In this note I recollect the important milestones, achieved in the period preceding the HERA era, in the high precision calculations of the radiative corrections to DIS, and in the development of the methods of their experimental control. I present subsequently the measurement strategies and discuss the advanced radiative correction tools for the HERA experimental program, with an emphasis on their role in the first, model independent, measurement of the partonic densities in the small-$x_{Bj}$ region. These notes are dedicated to Staszek Jadach as a contribution to the celebration of his 60th-birthday.