This standard serves as a reference for IEC 61513, which deals with the system aspects of high integrity computer-based I&C used in safety systems of nuclear power plants together. IEC 60880 is the second level SC45A document tackling the issue of software aspects for I&C systems performing category A functions. Software for category B and C functions is dealt with in IEC 62138. IEC 60880 and IEC 62138 together cover the domain of the software aspects of computer-based systems used in Nuclear Power Plants to perform functions important to safety. This version of IEC 60880 is to be read in association with IEC 60987 and IEC 61226, the appropriate SC45A standards on computer hardware and on classification.