Tutorial is an introduction to the basics of PLC programming. The SIMATIC S7-300 of Siemens was adopted as the basic controller, the syntax, semantics and programming principles in STEP7, the programming language of Siemens SIMATIC S7 industrial controllers, were considered. The description of the language is provided with numerous examples illustrating the features and capabilities of the STEP7. When describing the language and programming examples, much attention is paid to the main difficulties and errors that a programmer may encounter. The textbook is intended for students of electrical engineering specialties of universities studying programmable logic controllers. It can be useful for students and engineers who master the basics of controller technology.