Every Modula-3 program must have a single main module. For small programs, the main module may be the only module. Here is a short example.
MODULE Main;
IMPORT IO; (* So we can print things *)
VAR name: TEXT; (* a string called `name' *)
BEGIN
IO.Put("Enter your name: ");
name := IO.GetLine();
IO.Put("Your name is: " & name & "\n");
END Main.