Editing Modula-3 (section)

==Syntax==
{{Expand section|date=July 2011}}<!-- Still needs some fleshing out. -->
A common example of a language's [[Syntax (programming languages)|syntax]] is the [["Hello, World!" program]].

<syntaxhighlight lang="modula2">
MODULE Main; 
IMPORT IO;
BEGIN
  IO.Put("Hello World\n")
END Main.
</syntaxhighlight>

All programs in Modula-3 have at least a module file, while most also include an interface file that is used by clients to access data from the [[Modular programming|module]]. As in some other languages, a Modula-3 program must export a Main module, which can either be a file named Main.m3, or a file can call <code>EXPORT</code> to export the Main module. <syntaxhighlight lang="modula2">MODULE Foo EXPORTS Main</syntaxhighlight> Module file names are advised to be the same as the name in source code. If they differ, the compiler only emits a warning.

Other conventions in the syntax include naming the exported type of an interface <code>T</code>, since types are usually qualified by their full names, so a type <code>T</code> inside a module named Foo will be named <code>Foo.T</code>. This aids in readability. Another similar convention is naming a public object <code>Public</code> as in the OOP examples below.