Advanced Topics

Autocad File Formats

Every file in a computer is created as a particular type or format. For example, a Corel WordPerfect letter file is created as a WPD file. A standard AutoCAD drawing is created as a DWG file. The difference is the way that the application program reads and writes the file.

In the ‘olden' days when DOS was the common operating system, all files had a maximum of 8 characters in their name, followed by a period, followed by the extension. The extension was a 3-letter ‘code' indicating the type of file.

Example:DRAWING1.DWG DRAWING1 name of the file DWG extension

After the introduction of Windows 95, you may have more than 8 characters in a name (up to 256), but the 3-letter extension remains. Windows is even set up to hide these extensions from you in its default configuration.

While working with AutoCAD, it is important to know that there are several types of drawing files. Here are some of the common AutoCAD extensions/filetypes:

DWG - BAK - DWT - DWF -SV$ - DXF - WMF - 3DS - JPG

These are only a few of the file types that AutoCAD uses. There are many others that would be considered support files. Those listed above deal with various forms of drawing files. There are many other ways to save your drawing, but these are the common ones.

DWG – This is the standard AutoCAD drawing file format. The thing to remember is that older versions of AutoCAD cannot read files created on newer versions. The newest version can read any of the older files. If you are exchanging files with other companies, do not assume that they are using the same version you are. BAK – This is AutoCAD's backup file format. Whenever you save a drawing, AutoCAD will automatically create a duplicate backup file. This file has all the same information as the original, but a different extension. If your original file becomes corrupt, or unusable for any reason, you can rename the BAK file to a DWG file and open it as you would any other drawing file. DWT – This is a newer format (R14) that is used for drawing templates. Templates are the same as prototype drawings in that they contain all the setup parameters for certain types of drawings. They are essentially the same as a DWG file. DWF – This is also a new format. This is used when you want to create a drawing that is for use on the Internet or otherwise not editable. It is a Drawing Web Format. This type of file contains features that allow users to view drawings on the Web without having AutoCAD on their computer. You can also use the DWFOUT command to open the Plot dialog box pre-set to DWF setting. SV$ - This is AutoCAD's format it uses whenever it performs an automatic save. AutoCAD will save the file automatically within a pre-determined time frame. This is set in your preferences dialog box. You can also tell AutoCAD where you want your autosave files to go. Most computers are set to save to the Windows/Temp folder. If you need to recover a drawing from the autosave file, just rename it to a DWG format. DXF – This is not really an AutoCAD format, but one that you should be aware of. DXF stands for Drawing eXchange Format. This is a very standard format that is used but many different CAD and graphics programs. This allows users to exchange drawings even if they don't have the same program. When you use the DXF format, some objects may change their appearance when re-opened. As with DWG formats, DXF formats vary from different releases. You have the option of saving the files as a DXF or you can use the DXFOUT command, conversely DXF Files can be imported using the DXFIN command. WMF – This is a Windows Meta File. This file can be used if you need to use this drawing in a non-CAD program. For example, you may need to add a drawing of section of a drawing to a Microsoft Word document. You would use this format to do that. YOu can export only a portion of your drawing with the WMFOUT command. 3DS - This is an older extention for 3D Studio Max - a high level animation and rendering program. You can export from AutoCAD by using the 3DSOUT command. (No longer available in AutoCAD 2007.) JPG - Most people know JPG's as the common format on the internet for images. You can also export your drawing easily to a JPG now. Use the JPGOUT command and then choose between the viewport or selected objects. BMP - This is similar to a JPG, but exports a raster BMP file instead of a JPG. Use the BMPOUT command. Genrally JPG's are smaller and better for e-mail and websites. PDF - Although not a AutoCAD file format, you can now save your drawing as a PDF (Portable Document Format) so that others can read it with the common Adobe Acrobat Reader. Use the Saveas... PDF option. These are the common file types used in AutoCAD. The main thing to remember is that you have the option of sharing your drawing with people who don't have AutoCAD installed on their machines.