using .dll's
 

Ok so i did some research on .dll's and i understand how they are integrated into programs. Question is though why use them? The one example i saw was making a button that exits the app in a user control. This was then saved as a .dll and then imported to the toolbox to be used anywhere on a different app. Why not just hard code a button instead of going through all that trouble? Or is there some other use here that i'm just missing.

something else i noticed too....this one program i have been studying saves all the information as it's own extension 'filename.gdy' how are they doing? Does it have something to do with saving the info as a .dll specific to that program?

You se them so that you dont have a 90 mojob mb file for a simple hello world application.

If you for example uses libraries that other people have developed, within your application you might want to link with their library dynamically (using dll) instead of statically (compile it in to your executable). Because if they bugfixes their library which you uses, you dont want to recompile your application every time they fix bugs. When using dll:s you only have to overwrite the old dll file with the new one.

You also save memory. At any given time, there is only one one copy of a dll in a particular place that exists in your memory. Your O/S does some smart things with your processor to make it appear on the memory space of all programs. They are preffered because of the flexibility stuff Klaree stated above and also because after they are loaded...they are as fast as static librarys and function pointers.

If I am not mistaken dll's are also often used for plugins.