A flat-file database is a database stored in a file called a flat file. SQLite, MySQL, PostgreSQL, MSSQL, Sybase, DB2, MongoDB, CouchDB, and Flat File. Alternatively, a shoutbox may be loaded from a flat file. As distributed, the nameserver was backed by a flat file database. Historically, RADIUS servers checked the user's information against a locally stored flat file database. The preceding is an example of a simple flat file table formatted as comma-separated values. However, this presented a flat file system to the user. It uses a flat file database for both backend and frontend. This specifies a simple flat file database table using the CSV file format. A flat file can be a plain text file, or a binary file. The early Apple Macintosh also featured a flat file system, the Macintosh File System. PC-File was a flat file database computer application most often run on DOS.