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DLL

Posted on 1999-07-13
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Last Modified: 2010-05-02
Some question for you:

What is the utility of a DLL.

How can I do a DLL to give parameter to an application

Do you have an example of a DLL who pass some parameter and return a value

Thanks a lot


Eric
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Question by:ceb102298
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caraf_g earned 300 total points
ID: 1524249
A DLL allows you to share the same functionality between multiple applications without duplication of effort and by keeping the runtime files smaller than they would be if all the code in the DLL were included.

A DLL is one type of an application, so your second question doesn't really make sense, but if I read Application as ".exe", you're looking at it the wrong way around. Main applications use DLLs, not the other way around, and they pass parameters from and to functions in the DLL. In VB you create ActiveX DLLs which means that in order to access functionality in the DLLs you'll have to create object instances of public classes in the DLL.

I'll make up an example for you in a project group. Just hang on for a couple of minutes...
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by:caraf_g
ID: 1524250
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by:apratima
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..
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by:caraf_g
ID: 1524252
ceb, I just looked at your profile :-)
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by:BeedleGuis
ID: 1524253
small correction or elaboration on caraf_g's answer . . a dll is an application extension . .meaning that:
In computers, a dynamic link library (DLL) is a collection of small programs, any of which can be called when needed by a larger program that is running in the computer. The small program that lets the larger program communicate with a specific device such as a printer or scanner is often packaged as a DLL program (usually referred to as a DLL file).

The advantage of DLL files is that, because they don't get loaded into random access memory (RAM) together with the main program, space is saved in RAM. When and if a DLL file is needed, then it is loaded and run. For example, as long as a user of Microsoft Word is editing a document, the printer DLL file does not need to be loaded into RAM. If the user decides to print the document, then the Word application causes the printer DLL file to be loaded and run.

A DLL file is often given a ".dll" file name suffix. DLL files are dynamically linked with the program that uses them during program execution rather than being compiled with the main program. The set of such files (or the DLL) is somewhat comparable to the library routines provided with programming languages such as C and C++.


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by:BeedleGuis
ID: 1524254
copied directly from whatis.com . .  :-)
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by:BeedleGuis
ID: 1524255
oh yeah . .and here's an example of parameters passed and returned . . however useless it is:


Private Declare Function GetWindowText Lib "user32" Alias "GetWindowTextA" (ByVal hwnd As Long, ByVal lpString As String, ByVal cch As Long) As Long

Private Sub displaytitle()
    Dim strTitle As String * 254
    GetWindowText Me.hwnd, strTitle, 255
    MsgBox strTitle
   
End Sub
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by:caraf_g
ID: 2096559
The zip file mentioned in this thread has since been removed from my homepage.
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