Ventana Systems, Inc. of Harvard, Massachusetts was formed in 1985. Ventana Systems was developing large-scale simulation models that integrated both business and technical elements to solve difficult management problems. In this work they used existing products combined with custom code written in programming languages. Although it was possible to develop the models in this manner, it was difficult and very time consuming to find and correct imperfections in the models.
In order to decrease model development time, Ventana Systems began to create its own simulation language. This language, called Vensim, was originally developed as a Pascal extension so that models were developed in Vensim, then the model was translated to a Pascal program for execution. Accompanying this translation, a database of model structure was developed for processing by an external program then written in Lisp. The resulting system ran under the VMS operating system of Digital Equipment Corporation. Models were now constructed in Vensim language, and debugged with the aid of the model structure tools.
Beginning in 1988, the Vensim language and the support system were ported to the C language and the X-Window graphical environment. A prototype of the system was also ported to run under version 2 of Microsoft Windows. When version 3.0 of Windows was released, Ventana decided to make the software publicly available. In 1991, Vensim Version 1.50 was released. Version 1.50 was termed a technical release and was intended primarily for expert modelers with some experience developing and using dynamic simulation models.
Version 1.60 of Vensim was released in 1993. This version added a User’s Guide to the documentation and was designed to make it easier to use Vensim and to perform modeling. Version 1.60 also was released in a number of different configurations—Standard, Professional and DSS—to meet the needs of different users. Version 1.61 of Vensim was released in 1994. Version 1.61 included a number of changes urged on us by our user community and substantial enlargements to overall functionality. The DSS configuration of Version 1.61 was made available as a native 32 bit Windows NT (and Win32s) application. Version 1.61 was released with the same documentation used in Version 1.60.
Vensim 1.62 was released in 1995. Version 1.62 was the first release for the Macintosh operating system, supported true Monte-Carlo sensitivity simulations of models, and included significant revisions to the documentation. Version 1.62 also included a model reader that, in the same spirit as Adobe Acrobat, could be freely distributed allowing Vensim models to be examined and simulated without owning the Vensim software. In 1996 a configuration of Vensim called Vensim Personal Learning Edition was released. Vensim PLE was made available without charge for users in education and for individuals engaged in personal (non-commercial) learning of system dynamics.
Vensim 3.0 was released in September of 1997. Version 3.0 included a significant rewrite of the User Interface and an almost complete rewrite of the documentation. All configurations of Version 3.0 were released for Windows 95/NT, Windows 3.1, Macintosh and Power Macintosh. Version 3.0 of Vensim included the Vensim Model Reader, and a Vensim DLL that can be linked with other programming languages, including C, C++, Visual Basic, Delphi, and others.
Vensim 4 was released in November, 1999. Version 4 updated the user interface, included new sketch objects such as the input/output controls for mini-applications, featured live data connections to spreadsheets, improved the subscripting language and mechanics, and finally brought the graphical Venapp editor. A new configuration called Vensim PLE Plus was released, providing affordable simulation software with powerful capabilities.
Vensim 4.1 and 4.2 were released in 2000. These added a significant number of new functions to Vensim.
Vensim 5 was release in February of 2002. This is the first version of Vensim to have SyntheSim – the ability to simulate models quickly enough to see all the results instantly. This ability, clearly, depends on the speed of modern computers to work effectively. With Version 5 we provided access to all updates electronically via our website. Version 5.1, with ODBC database support was release in January of 2003. Vensim 5.2, with the new Reference Mode editing tool was released in August of 2003. Vensim 5.2a released in October of of 2003 enhanced the Reference Mode behavior and substantially improved the performance of the ODBC connections.
Vensim 5.3 released in January of 2004 added enhanced navigation capabilities that allow you to reference web pages and other files from within models and also to load different models and create sketch elements to run models. The copying and pasting functionality was made more flexible to give you more control over variable names created. This release also marked a change in PLE to allow the creation of multiple views. In version 5.3a released in April of 2004 we added in the ability to global rename variables making updating portions of a sketch easier.
With the release of Version 5.4 in July of 2004 Vensim PLE gained significant functionality important for learning and classroom use. Support for input/output objects allows for the creation of control panels with Vensim PLE and the ability to override behavior make the investigation of model behavior under SyntheSim even more effective.
Vensim 5.5 released in September of 2005 supported the publication of model packages that allow the inclusion of models and supporting files into a single package that can be sent to others.
Vensim 5.6 released in September 2006 supports Unicode making it much easier to work with models in different languages.
Vensim 5.7 released in July, 2007 added unchangeable constants, the VECTOR SELECT function and a rewrite of the optimizer to improve performance and controllability.
Vensim 5.8 released in August, 2008 added multiple thread support to improve performance and provided Japanese and Chinese (simplified) interface options.
Vensim 5.9 released in April, 2009 adds in Date and Time markings for graphs and tables to improve presentation.
Vensim is, and will continue to be, an evolving product. We periodically release engineering updates with additional functionality and bug fixes. Along with the continued development of the Vensim software, we are committed to maintaining Vensim PLE and will continue to make it available without charge for educational use.