This book is designed as a learning and working book for the programming language C. The reader learns to acquire algorithmic, structured thinking through a variety of problem-solving examples and to master basic concepts such as algorithms, variables, and modularity. The C programming language is very suitable for beginners, as it forms the foundation for modern object-oriented languages like C++, Java, and C#. C is also a flexible and efficient language that can quickly solve complex tasks. A special feature of the book is the thorough explanation and review of fundamental mathematical concepts, such as prime numbers, sets, fractions, matrices, equations, and geometry. The diversity of the topics presented makes the book interesting for advanced readers as well. Additional materials for the book are provided.