The focus of this textbook is on analytical functions, as well as the differentiation and integration of functions of a single variable. Concepts such as continuity and convergence of sequences and series are assumed. The material is illustrated and supplemented with numerous examples and exercises. The book is suitable for self-study but is primarily designed as a companion reading from the very beginning for a degree in mathematics, physics, and computer science. Its rigorous approach makes it easy to read and comparatively easy to understand.