A main module is an ordinary module, who's file name is given as parameter to the linker. The first instruction of a main module serves as the first instruction of the corresponding program produced by the linker. When the last instruction in the main module has been completed, the program terminates.
The name of the main module can also be given as a parameter to the interpreter, which will execute the instructions in the module without first compiling them, and do likewise for any imported modules.