Book excerpt: IAEA work in the area of research reactor operation and maintenance is aimed at enhancing the capabilities of Member States to utilize good engineering and management practices to improve research reactor reliability and availability. In particular, the IAEA supports activities addressing ageing management of research reactor instrumentation and control (I&C) systems. The purpose of this publication is to provide engineering guidance on the design, and operational aspects of digital I&C systems for the refurbishment of existing facilities and for new research reactors. Key areas addressed include codes and standards applicability, licensing issues, dealing with the change in human-system interface from analogue to digital technology, software verification and validation activities, periodic testing and inspection, and configuration management. The publication contains technical descriptions and summaries of available digital systems that have been utilized in both new research reactor designs, and in the upgrading of older analogue safety and control systems. This guidance is foreseen for the broad spectrum of research reactors types existing today.