Let X be a completely
regular Hausdorff space. Characterizations are obtained of the o-realcompact spaces
lying between X and its Stone-Čech compactification βX, and of those spaces lying
between X and its minimal c-realcompact extension uX. These results are used to
derive several necessary and sufficient conditions for the equality E(uX) = uE(X) to
hold, where E(X) is the absolute of X and uX is the Hewitt realcompactifioation of
X.