Feingold, Frenkel, and Ries defined a structure, called a vertex operator para-algebra, where a VOA, its modules and their intertwining operators are unified. For each $n \geq 1$, this book uses the bosonic construction (from Weyl algebra) of four level $-1/2$ irreducible representations of the symplectic affine Kac-Moody Lie algebra $C_n^{(1)}$.