Programming Basics: Hello World

You can divide your code into different modules. Many packages contain a main module, usually named Main.m3. The main module specifies the main body of your program. Here is an example of a main program:

MODULE Hello EXPORTS Main;
IMPORT IO;
BEGIN
  IO.Put ("Hello World\n");
END Hello.

To use another module, you import an interface exported by that module. In this example, we have imported only the IO interface to do simple input/output. By looking at the IMPORT clause, you can easily find out what interfaces a piece of code depends on.

The last part of each module is its body. In this case, we are calling the procedure IO.Put which prints the text string "Hello World" to the standard output.