  In this paper, the classification in [Lin,Wei,Ye] of solutions to Toda
systems of type $A$ with singular sources is generalized to Toda systems of
types $C$ and $B$. Like in the $A$ case, the solution space is shown to be
parametrized by the abelian subgroup and a subgroup of the unipotent subgroup
in the Iwasawa decomposition of the corresponding complex simple Lie group. The
method is by studying the Toda systems of types $C$ and $B$ as reductions of
Toda systems of type $A$ with symmetries. The theories of Toda systems as
integrable systems as developed in [Leznov, Saveliev, Nie], in particular the
$W$-symmetries and the iterated integral solutions, play essential roles in
this work, together with certain characterizing properties of minors of
symplectic and orthogonal matrices.
