The $E directive sets the extension of the executable file generated by the compiler. It is often used with the resource-only DLL mechanism. 

For example, placing {$E deu} in a library module produces a DLL with a .deu extension: filename.deu. If you create a library module that simply references German forms and strings, you could use this directive to produce a DLL with the .deu extension. The startup code in the runtime library looks for a DLL whose extension matches the locale of the system—for German settings, it looks for .deu—and loads resources from that DLL.