External function command declairs the external entry point to The DF system. The compiler creates a reference to the function complete with return type and parameter information. The macro also generates code that retains the name of the function and the name of the library in a runtime array. This array is used when the DLL is "loaded".
  #IF (!1=16)
    #SET ZK$ 1
  #ELSE
    #SET ZK$ 0
  #ENDIF