Instruct the compiler not to compile the file.
This looks like an odd directive. Since you can split your program in multiple files, and you can create configuration files, you might open a file and try to compile it. Only normal project files can be compiled and you will get a number of errors and also unwanted files like error, report, etc.
To prevent that you compile a file that is intended to be included, you can insert the $NOCOMPILE directive.
Then the file will only be compiled when it is called from your main file, or other include file.
A file that is opened as thus the main file, and which includes the $NOCOMP directive, can not be compiled.
The IDE will see it as a successful compilation. This is important for the Batch Compiler.