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Vensim Help

NOTE By default Vensim is allocated two megabytes of memory. If you are working with larger models you might want to increase this by clicking on the Vensim icon and using the File>Get Info command from the Macintosh Finder. Using less than one megabyte is unlikely to work.

Differences from Other Macintosh Applications

There are several differences between Vensim and most other Macintosh Application: The parent-child form of the user interface, the appearance of dialogs and the printing dialogs.

The user interface in Vensim is an extended multiple document interface in which all windows are maintained within a parent window. Because there are three different types of window — build, control and output — and because there can be tens or even hundreds of output windows, containing them within a parent makes it much easier to move between applications. This does, however, mean that Vensim appears as one big window containing numerous smaller windows instead of numerous small windows spread out across the desktop. The smaller windows are also sized following the Windows convention of dragging on their borders rather than the Macintosh conventions of dragging on the lower right hand corner. The parent window is sized following Macintosh conventions.

Dialogs on the Macintosh will appear quite similar to the way they appear on Windows. Buttons will be square and have a three dimensional appearance.

In some places Vensim will use file name with paths. Normally this is accessed through a file dialog and should be transparent. Nonetheless, there are many places where you might see file names such as :Macintosh HD:Vensim:models:butter.mdl. The colon : is used to separate folders. File extensions such as .mdl can be used to identify TEXT files as models.

Vensim uses its own print dialog. The standard dialog for printing that would normally be seen on a Macintosh does not appear.

Differences Between the Macintosh and PC

Vensim uses standard Macintosh file access dialogs. Because these are the standard dialogs they will look very different from other dialogs in Vensim.

Vensim for the Macintosh is constructed as a 32 bit application. This removes most of the limitations on model size, but the Macintosh operating system does impose several restrictions that do reduce capacity relative to Vensim DSS32 under Windows NT.

The compiled simulation and external function options of Vensim are not available on the Macintosh. The functions that communicate with spreadsheets (GET 123 DATA, GET XLS DATA, GET 123 CONSTANTS and GET XLS CONSTANTS) as no available on the Macintosh.

The Macintosh does not support hardware interrupts on floating point errors and therefore these are checked in software by Vensim. Normally both platforms will yield the same results. For example


will cause an error message to be reported at time 25. However, the equation

mytime = IF_THEN_ELSE(1/(25-Time),Time,-Time)

will cause an error message to be reported on the PC but not on the Macintosh.

Dialog boxes on the Macintosh have the standard Macintosh Tab behavior. You cannot use the Tab key to move between buttons.

The Macintosh has only one mouse button; the PC has two. Vensim uses a convention of left button (on the PC) or only button (on the Macintosh) for most mouse click operations. Setting options on sketch objects and Analysis tools is performed by a right mouse click (on the PC) or a combination Control key (or Apple key) plus mouse click (on the Macintosh).