When the editing process is over, both the original and the deitted file will be stored onto the disk. the original file the one which existed before editing , will be renamed with the same file name and an extension of BAK. the new file will ahve the name given with the Edin command .
For example say a file SAMPLE.TXT exists on a disk if you edit this file, make modifications and save it the edited wersion of the file will become SAMPLE.TXT and the original SAMPLE.TXT become SAMPLE .TXT. this facility allows you to recover the original file if required.
When you create a file first time editing , how ever the backup is not created
the file with the extension of BAK can not be edited directly , the user would have to rename the file, giving it some other name and use the new name for editing.