How does PowerBackup identify whether a file has been backed up or not?

During a Full or Incremental backup, PowerBackup un-checks the Archive attribute of the original files that have been backed up. The Archive attribute is used in the Windows system to identify whether or not a file has been backed up. When a file is created or modified, Windows automatically place a checkmark in the Archive attribute until the file has been backed up.

The difference between an Incremental and a Differential backup lies in how PowerBackup handles the Archive attribute of the files that are backed up. During a Differential backup, our program keeps the Archive attribute checked !V it means that PowerBackup will back up the file again on the next time the program encounters it. During an Incremental backup (as well as a Full backup), PowerBackup un-checks the Archive attribute. It means that the program will not back up the file on the next time the program encounters it.