What is DLL ? Definition

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A DLL is a dynamic link library. It is a collection of code and/or data, which may be used by several applications (or other libraries/modules).

By using a DLL, a program can be modularized into separate components. For example, an accounting program may be sold by module. Each module can be loaded into the main program at run time if that module is installed. Because the modules are separate, the load time of the program is faster, and a module is only loaded when that functionality is requested.