The IsDefined command returns true if the language lang has been defined for use by CodeGeneration, and false otherwise.

A language has been defined for use by CodeGeneration if it is one of the built-in languages provided with the package, or it has been added with Add or Define.

$\mathrm{CodeGeneration}\left[\mathrm{LanguageDefinition}\right]\left[\mathrm{IsDefined}\right]\left(''C''\right)$

$\mathrm{true}$