sentences:  For this reason, it is also used for backing up CDs and DVDs.Files that don't belong to installed programs can usually be backed up with file-based backup software, and this is preferred because file-based backup usually saves more time or space because they never copy unused space (as a "bit-identical" image does), they usually are capable of incremental backups, and generally have more flexibility.But for files of installed programs, file-based backup solutions may fail to reproduce all necessary characteristics, particularly with Windows systems.