  Based on the particular orderings introduced for the positive roots of finite
dimensional basic Lie superalgebras, we construct the explicit differential
operator representations of the $osp(2r|2n)$ and $osp(2r+1|2n)$ superalgebras
and the explicit free field realizations of the corresponding current
superalgebras $osp(2r|2n)_k$ and $osp(2r+1|2n)_k$ at an arbitrary level $k$.
The free field representations of the corresponding energy-momentum tensors and
screening currents of the first kind are also presented.
