Modelica language is useful for modelingthebehaviorofphysicalsystems. Modelica blocks are identical to Xcos blocks, with the exception that they are of implicit type. These blocks are denoted by a black square and the user can connect implicit blocks of the same domain. Modelicablocksin Xcos require a C compilersinceModelicatranslatesthesystemdirectlyintoaCfilethatisthenlinkedtotheXcos environment.The modelica error can be caused by a number of factors, the most common of which are an incorrect compiler or a lack of Visual Studio tools if you are using Windows OS. It is important that you paste the error message here in order to better understand the issue.