This International Standard supplements IEC 60964. It presents design requirements for the application of VDUs in main control rooms of nuclear power plants. For the main control room of a nuclear power plant, IEC 60964 includes general requirements for layout, user needs and verification and validation methods and these aspects are not repeated in this standard. IEC 61227, IEC 61771, IEC 62241 and IEC 61839 should also be read with this standard. This standard assists the designer in specifying VDU applications (including displays on individual workstations and larger displays for group-working or distant viewing) together with or instead of conventional (panel) displays by: – stating principles to take advantage of VDU capability; – giving examples of good practice and guiding the designer to avoid deficiencies of design. This standard contains: a) requirements for information needs: – according to information goals e.g. operation, maintenance, protection, – allowing for the necessary amount of space, e.g. location, arrangement, – using a hierarchy and/or relationships, – avoiding unnecessary information, – ensuring that information is relevant, b) requirements for good presentation such as: – clear and flicker-free display with suitable updating frequency, – enough display space and an optimal arrangement, – adequate format and symbol sizes, – pictorial, symbolic display in addition to alpha-numeric capacity, – standardized, common symbols and names, – arrangements oriented to human factor needs, e.g. population stereotypes, – use of grouping and coding methods, – use of consistent flow directions, – appropriate abstraction levels according to the needs of the different presumed users, c) methods for easy and quick access to the specific information of current interest: – by simple selection of single formats or format-sets according to information goals, – by using different kinds of menus (icons of neighbouring information) or other access techniques (last display, selection on screen, etc.) by soft keys on or off the VDU screens or cursors, – by using programmed presentation (triggered by any binary signal, such as an alarm), d) design criteria to obtain appropriate reliability of all functions necessary to achieve the specified information goals. This standard is intended for application to the design of new main control rooms in nuclear power plants designed to IEC 60964 and where this is initiated after the publication of this standard. If it is to be applied to existing control rooms or control areas designs, care should be taken as some assumptions made (such as automation level) may not apply. Where a deviation from this standard is necessary in a back-fitting application the reasons should be documented.