When the History is Truncate d, the information for the removed Time Step s is stored in a special data structure called a State Variable. The State Variable is an Assumption Variable.
A state variable preserves static state information in terms of variable values that are usually globally accessible. In an OO context all state variables are attributes of some object and all attributes are state variables. (See category on what OO is all about.)
(Or state parameter, thermodynamic variable.) A term for pressure, temperature, and specific volume; other thermodynamic quantities that depend on these or other variables are often referred to as thermodynamic functions of state. In this sense, the equation of state specifies the relation among the state variables.