What Exactly Does A .dll File Do?

[Skrip]

What exactly does a .DLL file do? I really don't know...

[Simucal]

Have a look at:

http://en.wikipedia.org/wiki/Dynamic-link_library

[SmOke_N]

Should be plenty of info here for you: http://www.google.com/search?q=define%3ADL...:en-US:official

[nfwu]

DLL: Dynamic-Link Library.

• A Shared library, usually have the file extention dll, sometimes ocx or drv.
• Same format as EXEs. Can contain code, data, resources, etc.
• Was created to save disk space and memory required for applications. Any code which many applications share could be separated into a DLL which only exists as a single disk file and a single instance in memory.
• Permitted modularity. (Allows changes to code an data in a self-contained DLL without needing to change the applications using the DLL)
• Usage as plug-ins. An interface can be created to allow new modules/plugins to be used at run-time. (Take AutoIt's plugin support and DLLCall as an example)
• 1 Drawback: DLL hell (that's what I call it, anyway). Multipule applications arguing about the version of a DLL to use.
  • Solution 1: place the different DLLs into the individual application folders, rather than a system-wide folder.
  • Solution 2: .NET
• An other usage of dlls are as resource DLLs, examples: icon libraries-extension ICL, and font files-extensions FON/FOT.

#)

EDIT: example of DLL code in C++:

#include <windows.h>

// DLL initialization
BOOL APIENTRY
DllMain(HANDLE hModule, DWORD dwReason, LPVOID lpReserved)
{
        return TRUE;
}

// Sample exported function
 __declspec(dllexport) int Add(int a, int b)
{
        return a + b;
}

Sample AutoIt calling code:

$answer = DllCall ( "sample.dll", "int", "Add", "int", 2 , "int", 8 )
MsgBox(0, "", $answer[0])

#)

Edited May 6, 2006 by nfwu

[slightly_abnormal]

what happends if u distrubute a program and the person doesn't have that dll, does everyone have a psapi.dll or user32.dll? or does autoit swallow the dll when converting to exe?

[dnsi]

No autoit does not do that. And oh the c++ example did not work. When i added 12 to 12 it came up with 0

[SmOke_N]

what happends if u distrubute a program and the person doesn't have that dll, does everyone have a psapi.dll or user32.dll? or does autoit swallow the dll when converting to exe?

If your unsure whether the end users computer will have the desired files needed to run your program, then it's a simple case of using FileInstall().

[w0uter]

No autoit does not do that. And oh the c++ example did not work. When i added 12 to 12 it came up with 0

the msgbox should have $answer[0] as dllcall returns an array. Edited April 16, 2006 by w0uter