  We prove that every C1 diffeomorphism away from homoclinic tangencies is
entropy expansive, with locally uniform expansivity constant. Consequently,
such diffeomorphisms satisfy Shub's entropy conjecture: the entropy is bounded
from below by the spectral radius in homology. Moreover, they admit principal
symbolic extensions, and the topological entropy and metrical entropy vary
continuously with the map. In contrast, generic diffeomorphisms with persistent
tangencies are not entropy expansive and have no symbolic extensions.
