The pressure was studied in a rather abstract theory as an important notion
of the thermodynamic formalism. The present paper gives a more concrete ac
count in the case of symbolic spaces, including subshifts of finite type. W
e relate the pressure of an interaction function Phi to its long-term time
averages through the Hausdorff and packing dimensions of the subsets on whi
ch Phi has prescribed long-term time-average values. Functions Phi with val
ues in R-d are considered. For those Phi depending only on finitely many sy
mbols, we get complete results, unifying and completing many partial result
s.