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There are two DoubleCAD file formats, 2CD, and 2CT that you can use for saving vector graphics from within DoubleCAD. *TC

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AnchorXted95302Xted95302W:* (TurboCAD for Windows) - a file format for saving vector graphics from within TurboCAD.
*TC AnchorXted95303Xted95303.Note: If you need to save a drawing that is to be opened by an earlier version of DoubleCAD, you can use Save As and save to one version back i.e. In DoubleCAD 4 You can save as DoubleCAD 3.

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Save proxy objects: saves ACIS solid and a number of other TurboCAD DoubleCAD Pro object with proxies so that TurboCAD Deluxe or Designer DoubleCAD XT can open the file and see representations of objects that are not supported by those applications. Proxies increase the size of the file, but do allow file to open more quickly.