What is .bak file? ZWCAD saves that for what?

Question: Hi I just began to use CAD, and I found that ZWCAD save .bak file for each .dwg in a folder. What does .bak file use for? How can I open it?

Answer: Hi, .bak file is a drawing backup file for CAD DWG file, which saved by ZWCAD. When you editing the DWG file, your previous revision saved by last time is stored in the .bak file. Why we need the .bak file? Because drawings can become corrupted due to a system crash, power failure, etc. When your drawing corrupt, you can still find your last revision from the .bak file, just change the extension .bak to .dwg, or use ZWCAD+ Drawing Recovery Manager to recover .BAK files automatically. 

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