This review considers the thermodynamic aspects of the theory of information processes--measurement, transmission of information, and its processing. Considerable attention is given to an explanation of the limiting relations between the accuracy of a physical measurement and the ensuing energy degradation. Hence, in particular, a relation is established between physical entropy and quantity of information. These results are used to determine the energy cost of information transmission with allowance for the energy expenditures on decoding. The process of information processing (computational process) is treated as indirect measurement, and on the basis of this model the energetic complexity of the process is determined (the minimum value of the energy that must be degraded in order to realize the prescribed processing with the necessary accuracy).