Vensim contains several types or classes of windows:
1. Build Windows are used for constructing new models, or for modifying, navigating, and simulating existing models. In Vensim Standard, Professional and DSS several models can be open at once, each in its own Build Window.
2. Output Windows are created by Vensim's Analysis tools, and include graphs, tables and lists.
3. Control Windows include the Control Panel, a tab dialog box used to control Vensim's internal settings, and the Subscript Control, used for defining and selecting subscripts in Vensim Professional and DSS.