Several problems were identified in digitalizing the I and C systems of NPPs. A scheme is divided into hardware and software to resolve these problems. Hardware verification and validation analyzed about common mode failure, commercial grade dedication process, electromagnetic competibility. We have reviewed codes and standards to be a consensus criteria among vendor, licenser. Then we have described the software licensing procedures under 10 CFR 50 and 10 CFR 52 in the United States Nuclear Regulatory Commision (NRC) and presented vendor`s approaches to scope with the licensing barrier. At last, we have surveyed the technical issues related to developing and licensing the high integrity software for digital I and C systems. (Author).