The basic theory of thermodynamics is treated in the book using ideal gas as an example. A clear explanation for the quantity entropy is given in the book. Analytic formulas for the mutual functional dependence of the quantities volume, pressure, temperature and entropy are given in the book in the case of an ideal gas. A thorough treatment of ideal gas thermodynamic processes is presented in the book. In a process two quantities are given as functions of time and other quantities are calculated as functions of time. I hope that the thorough treatment helps especially those people (for example students) who take their first steps in learning thermodynamics. The book includes a list of a computer program that calculates basic thermodynamic processes for an ideal gas. An example calculation for every process is presented in the book - input file is given and the result is presented as curves. Every curve is given a thorough description.