DrRacket supports multiple dialects of Racket, as well as some non-Racket languages. You specify a language in one of two ways:
Select the Use the language declared in the source option (via the Language|Choose Language... menu item), and then specify a specific language as part of the program usually by starting the definitions-window content with #lang.
Select the Language|Choose Language... menu item, and choose a specific language. After changing the language, click Run to reset the language in the interactions window. The bottom-left corner of DrRacket’s main window also has a shortcut menu item for selecting previously selected languages.
Using a language declared in a program’s source is the recommend mode, and it is described further in Language Declared in Source.
The Language|Choose Language... dialog contains a Show Details button for configuring certain details of the chosen language. Whenever the selected options do not match the default language specification, a Custom indicator appears next to the language-selection control at the top of the dialog.
See Languages (later in this manual) for more information on the languages that DrRacket supports.