As a verb, to "archive" means to copy files to a long-term storage medium for backup. It can also refer to the act of compressing a file. As a noun, an archive is a disk or tape or any other storage medium used to hold files that have been archived. In MS-DOS-based personal computers, archive is a file attribute designed as a precautionary measure to remind the user to back up important data. Files with the archive attribute are marked by the operating system if they have been modified since they were last backed up.