differential backup (operating system) A kind of backup that copies all files that have changed since the last full backup. Each differential backup will include all files in previous differential backups since the full backup so to restore a version of a file, you only need to search the full backup and the relevant differential backup.
Some systems support differential backup by associating an "Archive" flag with each file and setting this flag whenever the file is modified to indicate that it should be included in the next backup. A differential backup does not change this flag, whereas an incremental backup resets it. Last updated: 2004-03-05
