The complete list of definitions for quantities relevant in the analysis of SLD/LEP-1 results around the Z-resonance is given. The common set of conventions adopted by the programs TOPAZ0 and ZFITTER, following the recommendations of the LEP electroweak working group, is reviewed. The relevance of precision calculations is discussed in detail both for pseudo-observables (PO) and for realistic observables (RO). The model-independent approach is also discussed. A critical assessment is given of the comparison between TOPAZ0 and ZFITTER.