metasyntactic

Metasyntactic variables are placeholder names used in programming, documentation, and technical examples to stand in for real identifiers or data. They appear in code samples, tutorials, and explanations to illustrate concepts without relying on specific names or values. By using generic tokens, authors can keep examples language-agnostic and focused on structure rather than semantics.

Origin and terminology: The term derives from the idea of metasyntax or metalinguistic notation, descriptions about syntax rather than concrete code. In practice, metasyntactic variables have become a conventional tool in computing literature, with a preference for short, pronounceable words that are easy to read and distinguish.

Common sequences: The canonical set is foo, bar, baz, with qux often following. When longer sequences are used, it is common to see quux, corge, grault, garply, waldo, fred, plugh, xyzzy, thud, among others. Some communities substitute different names, such as spam and eggs, or use narrative names like Alice and Bob, depending on context.

Usage and purpose: Metasyntactic variables serve as neutral stand-ins for variable names, function identifiers, or data values. They help demonstrate algorithms, data flows, and interface contracts without implying real-world semantics. They also reduce naming conflicts in examples and make the material easier to adapt to different programming languages or domains.

Examples: A typical pseudocode example might assign foo and bar as temporary values to show a calculation, or define a function that takes baz as a parameter. Documentation often uses these tokens in diagrams or test case descriptions to convey generic behavior.

See also: placeholder name, metasyntax, variable naming conventions.