The textbook contains the basic concepts of the sections "PC Software," "Design and Programming Methods," "Methods for Assessing the Economic Efficiency of Investments in Information Technologies" of the discipline "Informatics and Programming." The functions of operating systems, the composition of application software from the user's point of view are discussed in detail. Designed for students of higher educational institutions studying in the specialty 080801 "Applied Informatics (by field)" (for bachelors and masters of the direction 230700 "Applied Informatics"), as well as for those who are interested in computer science and information technology.