  In this paper we present a discrete, non-perturbative formulation for type
IIB string theory. Being a supersymmetric quiver matrix mechanics model in the
framework of M(atrix) theory, it is a generalization of our previous proposal
of compactification via orbifolding for deconstructed IIA strings. In the
continuum limit, our matrix mechanics becomes a $(2+1)$-dimensional Yang-Mills
theory with 16 supercharges. At the discrete level, we are able to construct
explicitly the solitonic states that correspond to membranes wrapping on the
compactified torus in target space. These states have a manifestly
$SL(2,\integer)$-invariant spectrum with correct membrane tension, and give
rise to an emergent flat dimension when the compactified torus shrinks to
vanishing size.
