Dll file is a library of Data and Code that can be one at a time by several Application used. For example, in Windows operating systems file Comdlg32.dll functions related to Dialog Box got to do. In the result of any Application in Windows can be from the functions inside these DLLs are timely open the Dialog Box.

the main advantage of dll files is in re-use, as well as better use of system memory.

application dll in programming: use the dll files the program got to be quite Modular and component-management can be wrote.