Editing Modelica (section)

==Characteristics==
While Modelica resembles [[object-oriented]] [[programming languages]], such as [[C++]] or [[Java (programming language)|Java]], it differs in two important respects. First, Modelica is a [[modeling language]] rather than a conventional ''programming'' language. Modelica classes are not compiled in the usual sense, but they are translated into objects which are then exercised by a simulation engine. The simulation engine is not specified by the language, although certain required capabilities are outlined.

Second, although classes may contain [[algorithm]]ic components similar to statements or blocks in programming languages, their primary content is a set of ''[[equations]]''. In contrast to a typical assignment statement, such as
: <syntaxhighlight inline lang=modelica>x := 2 + y;</syntaxhighlight>
where the left-hand side of the statement is assigned a value calculated from the expression on the right-hand side, an equation may have expressions on both its right- and left-hand sides, for example,
: <syntaxhighlight inline lang=modelica>x + y = 3 * z;</syntaxhighlight>
Equations do not describe assignment but ''equality''. In Modelica terms, equations have no pre-defined ''[[Causal system|causality]]''. The simulation engine may (and usually must) manipulate the equations symbolically to determine their order of execution and which components in the equation are inputs and which are outputs.