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STELLA and iThink

STELLA and iThink

the bridge to the future of modeling

Product Description

Both STELLA and iThink allow you to quickly create system diagrams that can be simulated over time. Working in a completely risk-free environment, you can test hypotheses and policy interventions repeatedly until you achieve the outcomes desired. Discover hidden aspects of your system that lead to unexpected outcomes. STELLA and iThink also allow you to create a user interface on top of your system diagram that makes it easy to share your understanding of the system, run your scenarios as part of a presentation, and enable others to experiment with their own policy combinations.

STELLA is the leading systems modeling tool for education and research, used at all educational levels to stimulate learning for subjects such as economics, physics, literature, calculus, chemistry, and public policy. STELLA models allow you to communicate how a system works – what goes into the system, how those inputs impact the system, and what are the outcomes.

iThink is more commonly used for business applications, e.g., to simulate and improve business processes, understand the working of your business more holistically, and develop new and exciting business strategies. iThink includes strong communication features to share the interdependencies between processes and problems within your business, and to safely explore potential improvements.

New Product Features

Live Analytics

Dynamically explore model behavior using Stella Live™. On the Interface Layer, change any constants in the model by dialing them up or down and immediately see the results for all objects displayed directly on the diagram

Cycle Time

Time stamp and track material as it flows through the model in order to precisely compute how long different tasks and activities are taking

Delay Converters

Mark a Converter as changing over time in response to changes in its input as happens with SMTH1, SMTH3, DELAY, DELAY3 and related Builtins

Sketchable Graphs

Graphs can now take user input: you can create a sketch of the expected behavior of a model variable over time. When the simulation is run, you will be able to compare your sketch to the actual behavior of the variable. Sketchable graphs come in handy when you want users of your model to "put a stake in the ground" regarding the performance of the model. Discrepancies between expected and actual performance can motivate effective, efficient learning experiences.

Interface Control Shading

It is now possible to turn off shading for interface controls giving a cleaner more modern appearance to interfaces - supported on both the Desktop and Netsim. Use the Interface preferences dialog to change this.

Individually Controlled Tables

Tables now store information about reporting period and type of reporting individually so you can have different tables with different settings. Rerunning the model is no longer necessary when changing the report interval and other reporting options.

New Builtins

CTFLOW, CTMEAN, CTMIN provides more robust streams of values for the different random number Builtins. CTSTDDEV, CYCLETIME, THROUGHPUT as well as UNIFORM for random number generation and GAMMALN for statistical computations

Comparative Graphs and Tables

Whatever runs are held by the data manager will immediately be displayed in comparatives when you specify the variable

New File Structure

Keep your model files organized. Module files are stored in a folder prefixed with the model name so that you can save a separate copy of a model using modules in file, without changing the original model


  • Q. What's the difference between STELLA and iThink?

    A. From a functional perspective, the STELLA and iThink programs are virtually identical. Each is designed to facilitate the mapping, modeling, simulation, and communication of dynamic processes.

    The major difference between the two products is in their target markets and the corresponding Introduction to Systems Thinking books. STELLA is targeted toward individuals in educational and research settings. The Introduction to Systems Thinking for STELLA covers the natural and social sciences. Applications and sample models demonstrate how the software can be applied in Biology, Chemistry, Environmental Science, Economics, Psychology, History and Physics.

    iThink, on the other hand, is targeted toward an audience of users in business settings. The Introduction to Systems Thinking for iThink is written with the business user in mind. Applications and sample models cover the gamut of business uses including Business Process Re-engineering, Strategic Planning, Financial Analysis, Manufacturing, Operations Research, Forecasting, and Organizational Development.

    In deciding between STELLA and iThink, simply match the appropriate product to your own needs. If you're in an educational or scientific research setting, STELLA is the best match. If you're working with business-oriented issues, iThink is the likely candidate.

    Stella Professional is intended for all users regardless of the nature of their work.

  • Q. Can I open STELLA models using iThink and vice versa?

    A. Yes, whether you are using STELLA or iThink you can open both STELLA models (.stmx and .stm files) and iThink models (.itmx and .itm files).

    Stella Professional is designed to be compatible with, and can open, STELLA/iThink version 10.1 models (.stmx and .timx). Model files created by earlier versions of STELLA/iThink are not guaranteed to open correctly in Stella Professional.

  • Q. Are STELLA/iThink 10.1 compatible with Stella Professional 1.0?

    A. Version 10.1 supports the use of models created in Stella Professional and maintains model elements that have been customized in Stella Professional (such as fonts, sizes, and specialized layout with bezier curves). This allows you to do model development work in Stella Professional and Interface development work in Version 10.1.

  • Q. Will the Windows version of STELLA or iThink run Macintosh models and vice versa?

    A. If you are using a Windows computer you can open and run models that were saved on a Macintosh. You do not need to convert the models.

    If you are using a Macintosh computer and are running version 9 or later, you can open and run models that were saved on a Windows PC. You do not need to convert the models.

  • Q. Can I have both STELLA/iThink 10 and Stella Professional 1.0 installed at the same time on my computer?

    A. Yes, models can be shared between Stella Professional 1.0 and STELLA/iThink 10.1. Models created and saved in versions of STELLA/iThink before version 10.1 cannot be used in Stella Professional with reliability. Likewise, Stella Professional models cannot be used win STELLA/iThink versions earlier than 10.1.

  • Q. What are the system requirements for STELLA and iThink?

    A. STELLA, iThink, and Stella Professional are available in both Windows and Macintosh versions. Below are the minimum system requirements depending on the operating system of your computer.

    For Windows:
    • Microsoft Windows™
    • 256 MB
    • 200 MB of disk space
    • QuickTime
    For Mac:
    • Mac OS 10.6 or higher
    • Intel-based Mac
    • 256 MB
    • 200 MB of disk space
    • QuickTime
  • Q. Do STELLA and iThink run on 64-bit Windows 7/8 operating systems?

    A. Yes, STELLA and iThink will run on 64-bit Windows 7/8 machines with compatibility properties set as shown here.

    (Stella Professional does not require special settings in compatibility properties.)

  • Q. Do STELLA and iThink run on Mac OS X 10.7 (Lion)?

    A. Yes, version 10 and later of STELLA and iThink supports Mac OS X 10.7 (Lion) and 10.8 (Mountain Lion). Stella Professional requires at least Mac OS X 10.9 (Mavericks).

  • Q. Can models created with previous versions be opened in STELLA/iThink version 10?

    A. Opening a STELLA or iThink model that was created in a previous version will automatically translate the model so that it is compatible with version 10. Click here for details about how the software handles specific translation issues.

  • Q. How can I make my simulations run on the web?

    A. STELLA and iThink models can easily be published to the web using the isee NetSim add-on utility. isee NetSim allows anyone with a web browser the ability to interact with and run your simulations on the web. For more information about isee NetSim, Click Here

    Another option for running your simulations on the Web is to create a custom Web interface and extend your model using the isee.NET Framework Software Development Kit (SDK). For more information about isee.NET Framework, Click Here

  • Q. How can I integrate my model with other applications?

    A. If you want to link data to your model, you can set up dynamic data import/export links to Microsoft Excel. If you want to integrate your model with other applications or databases you can use the isee.NET Framework SDK to programmatically access the interface objects in your model.

    For detailed help information about isee.NET Framework, Click Here

  • Q. How do I bend a Flow in STELLA or iThink v10?

    A. Drop a Flow and start dragging it. When you want it to change direction at a 90 degree angle, hold the shift key while you move the cursor in the direction you want the Flow to go. For more tips and tricks about using STELLA and iThink, read our blog post.

  • Q. How do I set the precision level for more than one variable in a Table?

    A. To set the precision level for multiple variables in a Table, right click on the variable names in the Table that you want to change. Once you have selected all of the variables, double-click on the name of one of the selected variable to open the Format Variable Table dialog. For more tips and tricks about using STELLA and iThink, read our blog post.

  • Q. How do I delete a page on a Graph or Table Pad?

    A. To delete a page on a Graph or Table Pad in STELLA/iThink v10, click the page- turn button in the lower left hand corner of the Graph or Table Pad until the page that you want to delete is showing. Next, click on the button on the toolbar to select the Dynamite tool. Using the Dynamite tool, click on the page-turn button again and the page showing will be deleted. For more tips and tricks about using STELLA and iThink, read our blog post.

    To delete a page in Stella Professional, select the table and open the properties panel. Use the Green Plus button to add pages and the Red Minus button to remove pages.

  • Q. What is a Module?

    A. A Module is a container for lower-level model structure. It is designed to support a process of top-down model design and development. For more information and frequently asked questions about Modules, read our blog post.

  • Q. Why will a Module run by itself using "Run Selected Modules" but won't run in an upper level of the model hierarchy?

    A. If you have Connectors into a Module that are not being used or there are inputs inside the Module that have not been assigned, the Module will not run in an upper level of the model hierarchy.

  • Q. Where can I find help documentation for STELLA/iThink and Stella Professional?

    A. For STELLA and iThink: Click Here
    For Stella Professional: Click Here

  • Q. Why do I sometimes get a "File not Found" message when opening a model?

    A. It may be a missing picture, Excel spreadsheet or some other imported file. When copying a model from one computer to another, you may need to copy more than just the model file. If your model uses other files such as graphics, sounds or spreadsheets you’ll need to package all of them with the model file. For more details, read our blog post.

  • Q. Can I run a STELLA or iThink model from a Windows command line?

    A. Yes, you can open and run a STELLA/iThink model from a Windows command line. You can also perform a host of other operations using the command line. For more details, read our blog post.

  • Q. What is Spatial Map?

    A. Spatial Map is a stand-alone application that allows you to map array data in your model to color values or images so that you can view your data as three- dimensional, spatial information. In the spatial map, the x and y axes are defined by the bounds of the array and z is represented by a color or image. (Elevation and temperature are examples of z values.) To see an example, read our blog post.

  • Q. Do STELLA and iThink support matrix arithmetic?

    A. Yes, STELLA and iThink support matrix operations such as addition, subtraction, transposition, multiplication and division. For more details, read our blog post. Additional information for version 10 and later can be found here.

  • Q. Can I create causal loop diagrams (CLDs) in STELLA and iThink?

    A. Yes, you can build causal loop diagrams in STELLA and iThink using modules or delay converters. You can also link a CLD to a working stock and flow model. To learn more and see an example, read our Blog Post.

  • Q. Why is storytelling such a powerful feature?

    A. Storytelling is a feature unique to STELLA and iThink that allows you to present and explain your model piece-by-piece. Even more powerful, however, is the ability to show the behavior as the structure of the model unfurls. Through storytelling, you can clearly create and communicate the link between the structure of the system and the dynamic behavior. For more details, read our blog post.

  • Q. Why do I have to keep entering the registration number for STELLA or iThink on my Windows computer?

    A. Most likely, this is a permissions issue. To fix this problem, follow these steps:

    1. Close STELLA or iThink
    2. Double-click on the "My Computer" icon to open Windows Explorer
    3. Double-click on Local Disk (C:) (or wherever STELLA or iThink is installed)
    4. If you have a 64-bit operating system open Program Files (x86). Otherwise open Program Files and scroll down to the isee systems folder
    5. Double-click to open the isee systems folder and then open the STELLA 10.0 or iThink 10.0 folder
    6. Right-click on the STELLA.exe or iThink.exe file and select "Run As Administrator"
    7. Enter your name, organization and registration number one more time
    8. Close STELLA or iThink and re-open to verify you are no longer prompted to enter a registration number.
  • Q. How do I get the highest resolution graphics for including my model in a publication?

    A. Copy and then Paste into Word, PowerPoint, or Illustrator. For the highest quality, you must hold down the SHIFT key for the duration of the Copy command. I.e., either hold down Shift-Ctrl-C or hold down Shift and while it's down, select Edit->Copy, then let go of Shift. Note that on Windows, Quicktime for Windows also needs to be installed. That allows Word, PowerPoint, and Illustrator to understand the PCT format.


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