  These lecture notes were prepared as a basic introduction to the theory of
constrained systems which is how the fundamental forces of nature appear in
their Hamiltonian formulation. Only a working knowledge of Lagrangian and
Hamiltonian formulation of mechanics is assumed. These notes are based on the
set of eight lectures given at the {\em Refresher Course for College Teachers}
held at IMSc during May-June, 2005. These are submitted to the arxiv for an
easy access to a wider body of students.
