With every continuous function a on the complex unit circle
one can associate a sequence {Tn(a)}infinity
n=1 of Toeplitz matrices and a sequence {Cn(a)}
infinityn=1 of circulant matrices. By employing
some advanced results on the finite sections of Toeplitz operators,
we prove asymptotic estimates for the central columns of the matrices
Tn-1(a) - Cn
-1(a)as n goes to infinity. Our results generalize
and sharpen recent results by T. Strohmer and by F.-W. Sun, Y. Jiang,
and J. S. Baras, who also discussed the relevancy of the problem in
signal processing.