In modern society, where information technology and communications play an increasing role, information theory is becoming a necessary component of education for mathematicians, physicists, programmers, and engineers. The textbook is devoted to the basics of classical information theory. The first chapters contain the main theoretical provisions. Further, applications of information theory to the tasks of encoding and transmitting information are considered. The presentation is conducted at the most accessible level with an abundance of examples and a detailed analysis of tasks, so the book will be useful to a wide range of students of physical, mathematical and technical profiles. It will also come in handy for teachers, especially the second half, where a set of test tasks (20 options) is presented, containing test questions on the theory and selection of tasks.