An external function can reside in the same module (EXE or DLL) as an application, or in a separate dynamic link library. RexxRegisterFunctionExe registers external functions within an application module. External functions registered with RexxRegisterFunctionExe are available only to REXX programs called from the registering application.
The RexxRegisterFunctionDll interface registers external functions that reside in a dynamic link library. Any REXX program can access a dynamic link library external function after it is registered. A dynamic link library external function can also be registered directly from a REXX program using the REXX RXFUNCADD built-in function.