minimize    f(x)         ; 
 subject to                      C_e(x)  = b    ;
                        clow <=  C_i(x) <= cupp ;
                        xlow <=    x <= xupp ;
 

The general linear inequality constraints must have either an upper or lower bound, but need not have both bounds. The variables may have no bounds; an upper bound; a lower bound or both an upper and lower bound.