Due to the widespread development of "machine mathematics," mathematicians are increasingly interested in the issues of discrete mathematics, that is, mathematics that is not related to the concept of limit transition. The book gives an elementary introduction to this field, quite accessible to junior students of both mathematical and technical or humanitarian specialties. It sets out some questions of mathematical logic, "discrete" probability theory, matrix calculus, game theory, mathematical economics, etc. The presentation is accompanied by a large number of examples and tasks for exercises.