Instrumentation and control (I&C) systems important to safety may be implemented using conventional hard-wired equipment, computer-based (CB) equipment or by using a combination of both types of equipment (see Note 1). IEC 61513:2011 provides requirements and recommendations for the overall I&C architecture which may contain either or both technologies. The main technical changes with regard to the previous edition are as follows: - alignment with the latest revisions of IAEA documents; - alignment with new editions of IEC 60880, IEC 61226, IEC 62138, IEC 62340 and IEC 60987; - alignment with significant advances of software engineering techniques; - integration of requirements for staff training.