Dynamic Link Library (DLL)

A Dynamic Link Library, also known as a DLL, is a file that contains a range of functions that can be used by other Windows applications.

The standard functions in the Windows API are accessed using DLL files. For example the file USER32.DLL contains a lot of the functions used by the Windows user interface.

DLL's are usually denoted by the file extension DLL, but DLL's may also have other extensions such as .exe or .drv.

DLL's are not only supplied with the base Windows operating system, but most other software will include them as well as a way of making the software modular and being able to reuse existing code (or library functions).