In recent years the Standard Model of electroweak interactions has successfully passed a number of crucial tests, most notably in neutral current reactions and through the observation of W- and Z-bosons in proton-antiproton collisions. How ever, experiments are only beginning to verify one of the most basic consequences of its theoretical formulation as a local quantum field theory: quantum corrections as calculated in perturbation theory. Measurements that will be carried out at electron positron colliders at Stanford and CERN in the very near future will improve the accuracy by more than an order of magnitude. Thus either these crucial elements of the present theoretical framework will be confirmed or the road to physics beyond the Standard Model will be opened. A huge amount of theoretical work has been invested during the past few years to match the envisaged experimental precision. QED corrections, in particular from initial state radiation, will playa dominant role in the interpretation of measurements and have to be understood at a hitherto unrivalled level of accuracy. Analytical cal culations - either to a fixed order in a or by summing large logarithms to arbitrary order - are complementary to recent developments of Monte Carlo techniques in the simulation of events with multiple photon emission. Measurements with hadronic final states evidently require the understanding of hadronic corrections to high accu racy. Even purely leptonic reactions are influenced by hadronic interactions through vacuum polarization.

The production of heavy quarks in high-energy experiments offers a rich field to study, both experimentally and theoretically. Due to the additional quark mass, the description of these processes in the framework of perturbative QCD is much more demanding than it is for those involving only massless partons. In the last two decades, a large amount of precision data has been collected by the deep inelastic HERA experiment. In order to make full use of these data, a more precise theoretical description of charm quark production in deep inelastic scattering is needed. This work deals with the first calculation of fixed moments of the NNLO heavy flavor corrections to the proton structure function F2 in the limit of a small charm-quark mass. The correct treatment of these terms will allow not only a more precise analysis of the HERA data, but starting from there also a more precise determination of the parton distribution functions and the strong coupling constant, which is an essential input for LHC physics. The complexity of this calculation requires the application and development of technical and mathematical methods, which are also explained here in detail.