[en] During the operation of the NPP Krsko - NEK and other nuclear power plants, it has been recognized that certain issues related to the usage of digital equipment and associated software in NPP technological process protection, control and monitoring, are usually not adequately addressed in the existing programs and procedures. Moreover, often the problems related to the programmable digital systems usage are not understood correctly, which means that they can not be treated properly. Owing to the specifics of the programmable digital systems usage they have to be treated in a different way than other plant equipment and related documentation. The term as well as the process of Process Computers Configuration Control was introduced to control, among other issues, three 10CFR50 Appendix B quality requirements related to the Process Computers application in NPP: Design Control, Document Control, Identification and Control of Materials, Parts and Components. Based on the experience from NEK and published experience from other NPP and other organizations, this paper sheds light on specifics of the programmable digital systems usage in nuclear power plants. The wording Programmable Digital Systems was used rather than Process Computers, to emphasize wide area of applicability of this term: from simple digital components with burned-in programs to the PLC (Programmable Logic Controllers) and large process computer systems. In order to satisfy requirements of the Process Computer Configuration Control, specific characteristics and specific problems related to the usage of programmable digital systems require specific treatment of these issues. This paper describes those specific characteristics and traditional misunderstandings, false beliefs, false expectations and common errors that are most frequently committed in the life cycle of the programmable digital systems, as well as consequences and problems that could develop. The paper also refers to the regulations, industry standards and experience based good practice solutions that could prevent or resolve some problems related to the programmable digital systems usage in NPPs.(author)