The digital control technology has been applied step by step to the recent PWR instrumentation and control (I & C) systems, and also it is planned to apply it to all the I & C systems, including the safety grade systems related to the reactor safety for the Advanced PWR plant. The integrated digital I & C systems have also been updated to enhance the maintenance capabilities of the systems, to optimize maintenance activities and reduce workloads of maintenance personnel. As a result, the integrated digital I & C systems have been established which can be applied to the actual plants, and which can contribute to the enhancement of reliability, hardware reductions and maintenance workload reduction of about 20% in comparison with the latest plants.