The system interface layer is the lowest level of interface to an external system such as a networking subsystem. The system interface layer is composed of the basic DLL entry-point declaration, along with any record types and constants it might require.

The system interface layer does not have a public interface, nor is it intended that application programmers use this layer. Programmers extending VA Smalltalk / VAST Platform to support additional network protocols would need to implement a system interface layer for the network protocol.

This layer is not discussed in this book. Refer to the Programmers Reference for more information on interfacing to DLLs.