Dynamic Link Library

Dynamic link library is Microsoft’s implementation of the shared library concept in the Microsoft Windows and OS/2 operating systems. These libraries usually have the file extension DLL, OCX, or DRV.


What is Dynamic Link Library

A dynamic link library (DLL) is a collection of small programs. They can be loaded when needed by larger programs and used at the same time. The small program lets the larger program communicate with a specific device, such as a printer or scanner. DLL files that support specific device operation are known as device drivers.

A dynamic link library (DLL) is a shared program module with ordered code, methods, functions, enums and structures. That may be dynamically called by an executing program during run time. A DLL usually has a file extension ending in .dll. Other file extensions are .drv and .ocx. DLLs were developed by Microsoft and work only with the Windows operating system (OS).

Advantage of Dynamic Link Library

The advantage of DLL files is space is saved in random access memory (RAM) because the files do not get loaded into RAM together with the main program. For example, as long as a user is editing a document in Microsoft Word, the printer DLL file does not need to be loaded into RAM. 

A program is separated into modules when using a DLL. And therefore have faster load times and be updated without altering other parts of the program. DLLs help operating systems and also programs run faster, use memory efficiently and take up less disk space.

Other Advantage of Dynamic Link Library

Another advantage of DLL files is that they may be used by multiple programs simultaneously. DLL files are usually not opened directly because they are automatically loaded with the program. DLL files also use system resources efficiently and reduce swapping.

Explaining Dynamic Link Libraries

DLLs help conserve system memory. They are not loaded into RAM until they are needed, and thus help reduce memory overhead. Applications that require DLL data receive it as required, which also helps manage memory.

Links to required DLL files are usually created during programming. If the links are static, DLL files are available and likewise used as the program runs. When DLL functions change, it is not necessary to recompile or relink the application using the DLL as long as the calling conventions, function arguments and return values remain the same.

Functions of Dynamic Link Library

  • Exported Functions -intended to be called by other modules, as well as from within the DLL where they are defined.
  • Internal functions -typically intended to be called only from within the DLL where they are defined.

To Wind Up

DLLs provide a way to modularize applications so that their functionality can be updated and also be reused more easily. DLLs also help reduce memory overhead when several applications use the same functionality at the same time. Because although each application receives its own copy of the DLL data, the applications share the DLL code. Some DLLs are provided with the Windows operating system and likewise available for any Windows application.

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