The purpose of this guide is to provide the reader with a comprehensive understanding of technical thermodynamics and its computational methods, with particular emphasis on the thermodynamics of gaseous and vaporous substances. I found it appropriate to divide the teaching material into a theoretical part A, which covers the scientific and mathematical foundations, and a practical part B, which describes the most important applications in engineering. For the sake of a concise and clear presentation, I have omitted the historical development up to the present day and have only included the underlying experimental research and its theoretical evaluation in the most significant results. References for further study are provided. The guide does not require any prior knowledge of thermodynamics.