Overview
A "flat file" is a plain text or mixed text and binary file which usually contains one record per line or 'physical' record (example on disc or tape). Within such a record, the single fields can be separated by delimiters, e.g. commas, or have a fixed length. In the latter case, padding may be needed to achieve this length. Extra formatting may be needed to avoid delimiter collision. There are no structural relationships between the records.
Typical examples of flat files are /etc/passwd and /etc/group on Unix-like operating systems. Another example of a flat file is a name-and-address list with the fields Name, Address, and Phone Number.
A list of names, addresses, and phone numbers written on a sheet of paper is a flat file database. This can also be done with any typewriter or word processor. A spreadsheet or text editor program may be used to implement flat file databases.
Read more about this topic: Flat File Database