Four-letter abbreviation

"Flab" redirects here. For other uses, see abdominal obesity.

A FLAB is an abbreviation using four letters. It is an abbreviation of Four Letter ABbreviation. It extends the self-referential humour of the TLA (Three Letter Acronym). It is sometimes referred to as an ETLA or XTLA (Extended Three Letter Acronym)

Description

In a world where every possible Three Letter Acronym has been registered as a .com, and almost every pronounceable one has many usages, there is a lot more scope for a unique name and greater readability with four letters. Using only upper-case English letters, there are 26⁴ = 456,976 possible four-letter abbreviations. If numbers, special characters, or case-sensitivity are allowed, many more FLABs are available.

FLABs are commonly used as codes within computer file formats and computer protocols where a compromise needs to be found between human readability and a fixed format. Many file formats such as TIFF and PNG use four-letter codes to identify the type of chunks. The developers of the Apple Macintosh operating system used four-letter abbreviations as type codes and creator codes. The Simple Mail Transfer Protocol (SMTP) introduced the idea of using four-letter abbreviations as codes for commands (e.g. HELO, QUIT).

In some of these contexts, the FLAB is called a FourCC (an abbreviation of Four Character Code) or OSType.

See also

• Three Letter Acronym
• List of acronyms and initialisms
• List of computing and IT abbreviations
• Four-character idiom