A DLL is a collection of subroutines and functions that have been compiled and linked. When you declare these functions or subroutines in an ESL application, that application can then call them directly.

You can extend the functionality of your application by putting new functions and subroutines in a DLL. Different applications can share common code that is loaded into memory only once. You can also maintain the DLL code without having to modify the ESL code that calls it as long as you do not change the interface between ESL and the DLL.