<operating system> A kind of backup that copies all files which have changed since the date of the previous backup. The first backup of a file system should include all files - a "full backup". Call this level 0. The next backup could also be a full level 0 backup but it is usually much quicker to do a level 1 backup which will include only those files which have changed since the level 0 backup. Together the level 0 and level 1 backups will include the latest version of every file. Level 1 backups can be made until, say, the backup tape is nearly full, after which we can switch to level 2. Each level includes those files which have changed since the last backup at a lower level. The more levels you use, the longer it will take to restore the latest version of a file (or all files) if you don't know when it was last modified. Compare differential backup. (2004-03-01)

An incremental backup is one in which successive copies of the data contain only the portion that has changed since the preceding backup copy was made.Description of Full, Incremental, and Differential Backups.

<operating system> ("back up" when used as a verb) A spare copy of a file, file system, or other resource for use in the event of failure or loss of the original. The term commonly refers to a copy of the files on a computer's disks, made periodically and kept on {magnetic tape} or other removable medium (also called a "dump"). This essential precaution is neglected by most new computer users until the first time they experience a disk crash or accidentally delete the only copy of the file they have been working on for the last six months. Ideally the backup copies should be kept at a different site or in a fire safe since, though your hardware may be insured against fire, the data on it is almost certainly neither insured nor easily replaced. See also backup software, differential backup, incremental backup, full backup. Compare archive, source code management. (2004-03-16)