Intended for systems engineers, software engineers, and electrical engineers in all fields, this book provides the first detailed description of a set of languages for modeling reactive systems, which underlies the STATEMATE toolset. One key language is Statecharts (invented by author David Harel), perhaps the most popular approach to date for the development of real-time systems. The syntax of the languages is described in a precise and complete manner, and the semantics are developed in a way that clearly and intuitively renders the behavior of modeled systems.