A DLL is a library of compiled code which other applications can use.
For example, when an application needs to get the time, it will call a function stored in Windows' core DLL library (kernel32.dll)
DLLs can be written in many different languages - and there are various standards which enable DLLs written in different languages to communicate with each other, for DBPro, DLLs written in C++ or Delphi are the most common. In the same way that Windows applications all use the same EXE file format, all DLLs will use a certain format.
In DBPro terms, a DLLs provide a way of adding new commands to the language. You place the .dll file in the <DBPro Program Folder>CompilerPlugins-user folder, and any new commands it contains instantly become available to use in your DBA source code.
BlueGUI:Windows UI Plugin - All the power of the windows interface in your DBPro games.