DLL

DLL

(1) See data link layer.

(2) (Dynamic Link Library) An executable program module in Windows that performs one or more functions at runtime. DLLs are not launched by the user; they are called for by an executable program or by other DLLs. The Windows OS contains a huge number of DLLs. With only one instance of the DLL open in memory, its routines can be shared by all running applications (see re-entrant code).

DLLs can perform a simple function such as drawing a 3D border around a dialog box, or they can be as large as a full-blown language system, such as one of the Visual Basic runtime modules (see VBRUNxxx.DLL).

Application DLLs
Many programs have a huge cadre of functions that are only used occasionally. Breaking up an application into separate DLLs saves memory by keeping routines on the hard disk until required. Application DLLs can also be made sharable.

The Unix equivalent of a DLL is a "shared library." Prior to Mac OS X, which is Unix based, the DLL equivalents in the Mac were called "extensions."

Need a DLL?
To replace a corrupted DLL or find a missing DLL, visit www.afreedll.com. See DLL hell.

---

1.	(networking)	DLL - Data Link Layer.
2.	(library)	DLL - Dynamically Linked Library.
3.		DLL - Dial Long Line equipment.