This monograph is devoted to covering the main results in the
qualitative theory of symplectic difference systems, including linear
Hamiltonian difference systems and Sturm-Liouville difference equations,
with the emphasis on the oscillation and spectral theory. As a pioneer
monograph in this field it contains nowadays standard theory of
symplectic systems, as well as the most current results in this field,
which are based on the recently developed central object - the
comparative index. The book contains numerous results and citations,
which were till now scattered only in journal papers. The book also
provides new applications of the theory of matrices in this field, in
particular of the Moore-Penrose pseudoinverse matrices, orthogonal
projectors, and symplectic matrix factorizations. Thus it brings this
topic to the attention of researchers and students in pure as well as
applied mathematics.