.CDC File Extension
File TypeAutoCAD DesignCenter Preview Cache File
What is a CDC file?
Icon preview created by the AutoCAD's DesignCenter tool palette; stores a small preview image that was generated when the user browsed a drawing directory using the Large Icon view; used for caching thumbnail images so that AutoCAD does not need to regenerate previews each time the user browses drawings.
CDC files can safely be deleted without affecting the original drawings. However, if you browse the same drawings again, the CDC files may be recreated.