What is Ment By DLL ?
 

A DLL (Dynamic Link Library) is a file that can be loaded and executed by programs dynamically. Basically it’s an external code repository for programs. Since usually several different programs reuse the same DLL instead of having that code in their own file, this dramatically reduces required storage space. A synonym for a DLL would be library.

A data definition language or data description language (DDL) is a syntax similar to a computer programming language for defining data structures, especially database schemas.