The main difference between the book and the existing ones is a detailed and systematic presentation of achievements in the field of experimental theory, which is beginning to find wide application in solving problems of technical diagnostics of discrete devices and systems with memory, including computers and control machines. Each chapter of the book contains examples and ends with tasks, which facilitates deep study and assimilation of its content. The book is a good teaching tool for students, engineers and scientists involved in the study of finite state machine theory and its practical applications.