What Are .DLLs?

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http://live.pirillo.com/ – What – exactly – is a .DLL? Why are there so many on your computer? Are they necessary?

A .DLL (or Dynamic Link Library ) is a software component that an application links to at run time. A .DLL file enhances the functionality of an .exe (or executable ) file. A .DLL file is executable, but not by itself. It must be ‘called upon’ by the .exe in order to work. You can’t, for instance, double click on a .DLL file and have it actually DO something. It needs the .exe in order to run.

Let’s talk a bit about “DLL Hell.” If you were to scan around your C: folder, you will probably see many different .DLL files that are basically the same… just in several different locations. This may seem like a nuisance, and you’ll find the urge to get rid of them. However, be careful. Many programs may require that same .DLL in order to run… but the programmer could have hard coded the files to HAVE to be in a certain location. Let’s say Program A needs .DLL A in order to run, and it’s located in C:Windows. Program B also needs .DLL A in order to run, but it has to be located in C:WindowsSystem32. If you delete one of those, one of the programs will no longer work properly. It will look for the .DLL file in the location it expects. When it doesn’t find it there, it won’t run.

You can find more information about .DLLs in general on Chris Quirke’s excellent tutorial. Chris is a Microsoft MVP, with a lot of respect for his knowledge of computers.

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