Carnot's theorem and Szilárd engine

Abstract: In this work, the relationship between Carnot engine and Szil\'ard engine was discussed. By defining the available information about the temperature difference between two heat reservoirs, the Carnot engine was found to have a same physical essence with Szil\'ard engine: lossless conversion of available information. Thus, a generalized Carnot's theorem for wider scope of application can be described as "all the available information is 100% coded into work".