Old extension is associated with backup file. You have chance to open old files with relevant softwares.
Old extension comes from English old word. During the backup process, some softwares takes copy of file and changes the old extension of file with Old. In this case, it avoids any misunderstanding.
Example: If you want to use a file called "document.doc.old", it is enough delete old word from the extension (you should click on "change name" option)
What to use old
Software which develops the file.
which page related to old file
old Related Searches
You can check related links about old fileextension.