Applies to any software forming part of a safety-related system or used to develop a safety-related system within the scope of IEC 61508-1 and IEC 61508-2. Provides requirements: - for safety lifecycle phases and actvities - for informatin relating to the software safety validation - for the preparation of information and procedures concerning software - to be met by the organisation carrying out modifications to safety-related software - for supporting tools. Has the status of a basic safety publication in accordance with IEC Guide 104.