We study the quantitative behavior of a two-component polymer blend in the presence of an impenetrable interacting surface. A solution of the problem for ring chains is given, which can also describe the behavior of linear chains. While first-order perturbation theory is used for the interactions between the different monomers, the interactions between the monomers and the surface are taken into account to all orders. The monomer concentrations on the surface are found to be linear functions of the bulk concentrations only in the absence of interactions between the two components. The deviation from linearity between the surface and the bulk concentrations increases on increasing both the intensities of all three different interactions and the molecular weights of the polymers. Surface enrichment of one of the components is enhanced when the difference between the two surface interactions increases and reaches its largest value near the coexistence curve of the corresponding phase diagram of the blend. The theoretical predictions compare well with experimental results found by means of scattering and other spectroscopic techniques.