  A string in four dimensions is constructed by supplementing it with forty
four Majorana fermions. The later are represented by eleven vectors in the
bosonic representation $SO(D-1,1)$. The central charge is 26. The fermions are
grouped in such a way that the resulting action is world sheet supersymmetric.
The energy momentum and current generators satisfy the super-Virasoro algebra.
GSO projections are necessary for proving modular invariance. Space-time
supersymmetry algebra is deduced and is substantiated for specific modes of
zero mass. The symmetry group of the model can descend to the low energy
standard model group $SU (3) \times SU_L (2) \times U_Y (1)$ through the
Pati-Salam group.
