The theory of linear codes over fnite rings has been generalized to linear
codes over infnite rings in two special cases; the ring of p-adic integers
and formal power series ring. These rings are examples of complete discrete
valuation rings (CDVRs). In this paper, we generalize the theory of linear
codes over the above two rings to linear codes over complete local principal
ideal rings. In particular, we obtain the structure of linear and constacyclic
codes over CDVRs