An iterative method based on perturbation theory in matrix form is des
cribed as a procedure to obtain the eigenvalues and eigenvectors of sq
uare matrices. Practical vector notation and elementary schematic algo
rithm codes are given. The particular programming characteristics of t
he present computational scheme are based upon eigenvector corrections
, obtained through a simple Rayleigh-Schrodinger perturbation theory a
lgorithm. The proposed methodological processes can be used to evaluat
e the eigensystem of large matrices.