What is DWG format? What program open .DWG file?

Question: I received a .dwg file of a drawing in an e-mail, but none of the programs on my computer will open the file to let me view it. Which programs will let me?

Answer: Hi, DWG means drawing, it is a CAD file. You will need to have the AutoCAD program or ZWCAD+program to open it. ZWCAD+ provide 30 days for free trial. 

Here are some information from wiki: 
DWG(DraWinG) is a binary file format used for storing two and three dimensional design data and metadata. It is the native format for several CAD packages including AutoCAD, ZWCAD and so on. The .bak (drawing backup), .dws (drawing standards), .dwt (drawing template) and .sv$ (temporary automatic save) files are also DWG files. 


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You may like more threads about “dwg” on CAD forum: 

DWG to WMF converter?

How to convert AutoCAD DWG to PDF?

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