DLL <--- WTH are they?

Ok I'm just getting into Windows programmming and well I'm trying to write a simple app but I fear it may not be so simple by the time I get to the end. As this is my first time at GUI programming (Save the occasional Flash MX work) I'm having a go at the windows thing.
What I wish to know and have explained to me are DLL (I know what it stands for) but their purpose and how they function is still beyond me. I'd like it explained by a programmer as opposed to reading tutorial texts. Afraid this is the best way I learn and teach. Thank you for your time :)

Hmm, I'll give this one a shot, feel free to barge in if you think I'm talking nonsense. ;)

Okay, suppose you had a function, we'll call it MyAmazinglyCoolFunc, and you wanted to use that function in all the programs you make. You could declare that function and all it's code in each of your programs' source, but that may make maintenance difficult, as you might have multiple copies of the same thing, so you may only update MyAmazinglyCoolFunc in some of your programs but forget to do it in all of them.

Putting your function into a DLL effectively modularises it, so you need only update it in the DLL's source, all the programs you make link to that DLL and use that single derfinition of the function, saving space in each of your programs. :cool:

DLL stands for Direct link library

It stands for Dynamic Link Library actually, but that wasn't the question being asked:-

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Originally posted by WDT
What I wish to know and have explained to me are DLL (I know what it stands for)...

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>> DLL stands for Direct link library

WTF? It stands for dynamic-link library.

Thanks to all of you ppl who responded (Yes; it's Dynamic Link Library for those of us that didn't know) Just to clarify it's basically a collection of function declarations and definitions?? And it needs to be compiled into the program too?

The code that makes up the functions isn't compiled into the programs, no, just a reference to them. The DLL is compiled code, it contains a table at the start of the file that describes where the code for each function is inside it. All you need is either the .lib file generated at its compilation or the compiler-specific dllimport statement and you can link to it.

ok so to get this straight. What goes in the DLL file if I were to try and make one? And from what SMurf says the function definitions would then go into a .lib file, 's just if I were to make one I need to know what the standard practice is.