The pressure was studied in a rather abstract theory as an important notion of
the thermodynamic formalism. The present paper gives a more concrete account
in the case of symbolic spaces, including subshifts of finite type. We relate the
pressure of an interaction function Ф to its long-term time averages through the
Hausdorff and packing dimensions of the subsets on which Ф has prescribed
long-term time-average values. Functions Ф with values in R^d are considered.
For those 8 depending only on finitely many symbols, we get complete results,
unifying and completing many partial results