This textbook is aimed at students and ambitious practitioners who are interested in the theory of programming and the semantics of programming languages, while also wanting to learn about newer concepts. The data flow of an imperative and nondeterministic programming language and the control flow of a variable-free language are initially described separately and then combined into a unified semantics for parallel programs. Special attention is given to the study of the mathematical relationships between different semantic approaches. The book is fully equipped with easily understandable proofs and practically relevant examples, and it includes not only larger case studies but also exercises with sample solutions as well as a wide selection of literature.