  Since the discovery of high-Tc cuprate superconductivity in 1986 many new
experimental techniques and theoretical concepts have been developed. In
particular it was shown that the BCS theory of d-wave superconductivity
describes semi-quantitatively the high-Tc superconductivity. Furthermore, it
was demonstrated that Volovik's approach is extremely useful for finding the
quasiparticle properties in the vortex state. Here we survey these developments
and forecast future directions.
