What are the advantages of using DLLs?

Hello y'all again!

I'm using Tpw1.5. I know how to write DLLs, but why might they be better
[on memory and resources] for a [large] program? Do they take up less
stack space than to have those  same procedures in the main program?

"To mangle the Turing Test... If ya can't tell, it doesn't matter."
 -a very wise comment from 'Tangent of the Arc' (moc.1cb@llahd)