This introduction to theory consistently focuses on current applications. Whether it's search engines, workflow management systems, web services, encryption of information, or authentication protocols – all these technologies are based on theoretical foundations of computer science. Thus, the book helps students not only to learn the fundamentals of theoretical computer science but also to apply them in order to effectively and productively contribute to information technology problem-solving. Due to its specific content and didactic quality, the book is suitable not only for use in teaching but also for self-study.