Dynamic Link Library

What Does Dynamic Link Library Mean?

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.

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DLLs were developed by Microsoft and work only with the Windows operating system (OS).

Techopedia Explains Dynamic Link Library

DLL-defined function types are as follows:

  • Exported: May be called by another module, as well as from their defined DLLs
  • Internal: May only be called from their defined DLLs

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 used as the program runs. If the links are dynamic, DLL files are used only as needed.

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.

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.

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Margaret Rouse

Margaret Rouse is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical, business audience. Over the past twenty years her explanations have appeared on TechTarget websites and she's been cited as an authority in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine and Discovery Magazine.Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages. If you have a suggestion for a new definition or how to improve a technical explanation, please email Margaret or contact her…