Info please on .dll files!

  Memoryman 17:30 26 Sep 2004

This isn't really a problem - but I'd like to know the answer! Yesterday I tried to use Windows Paint and got an error message saying the file MFC42.dll was missing or corrupted. So I uninstalled Paint from Windows Components and then re-installed it. This brought Paint back to life. I did a search to see where the replacement MFC42.dll was and was amazed to find 17 copies on the machine, of many different version numbers, and widely scattered in various folders - some in Windows and others in specific programme files. I'd always thought the idea of .dll files was to have ONE copy which all the various applications used. So why are there so many scattered about??
A further search revealed that there are many versions of several other .dll files.
Thanks for your help!

  Valvegrid 17:50 26 Sep 2004

Its very basically a file that contains data. When you run a program the program asks the computer for the data that is contained in the dll file and were to find it. Every time you load a new program it loads a number of dll files for it to use, not every program needs them incidentally. The location of the dll file is unimportant, as long as the program that uses it knows were to find it, this is why quite often they are duplicated all over the computer.

There are programs that you can run that will check if a program is asking for the dll, if it isn't it will mark it for deletion. You haven't mentioned what operating system you are using, but if you do someone will probably point you to such a program.

  barnacarry 18:22 26 Sep 2004

I found this and hope this also helps -
Understanding DLL Files
A dynamic-link library (DLL) file is an executable file that allows programs to share code and other resources necessary to perform particular tasks. Microsoft Windows provides DLL files that contain functions and resources that allow Windows-based programs to operate in the Windows environment.

DLLs most often appear as files with a .DLL extension; however, they may also have an .exe or other extension. For example, the Shell.dll file provides the Object Linking and Embedding (OLE) drag-and-drop routines that Windows and other programs use. The Kernel.exe, User.exe, and Gdi.exe files are examples of DLLs with .exe extensions. They provide code, data, or routines to programs running in the Windows operating system. For example, one of these files provides the "CreateWindow" function that programs use when a new window is created on the screen. In Windows, an installable driver is also a DLL. A program can open, enable, query, disable, and close the driver based on instructions written in the DLL file.

DLLs can be found in the Windows directory, the Windows\System directory, or a program's directory.

If you start a program and one of its DLL files is missing or damaged, you may receive an error message such as "Cannot find xyz.dll." If you start a program that has an outdated DLL file or mismatched DLL files, the error message "Call to undefined dynalink" might appear. If this happens, you must get a copy of the DLL file and put it in the proper directory before the program will run correctly.

To determine the origin of a DLL file

Click Start, point to Find, and then click Files or Folders.
In the Named box, type the name of the file you want to find—, for example "shell32.dll" (without the quotation marks)#151;click Local Hard Drives or the drive letter you want to search in the Look In box, and then click Find Now.
In the list that appears, right-click the file, click Properties, and then click the Version tab.
If the file is a Microsoft file, extract a new copy of the file. For information about extracting Windows files, see see Knowledge Base article number Q129605, "How to Extract Original Compressed Windows Files."

If the Company Name referenced on the Version tab is different than Microsoft, contact the manufacturer for assistance.

This information is also available in the Microsoft Knowledge Base. If you would like to view this information online, see Knowledge Base article number Q87934, "Definition and Explanation of a .DLL File."

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