When I finish my site i plan to have a www.example.com/download folder
but inside this folder i'm going to have files like .txt and .c etc..
when i link to these files i want them to pop up as a download instead of showing them as a text file on the internet page
It's impossible to force browser behavior when it comes to file types. You can try to influence it, but ultimately, the visitor/browser has final say in how it handles files. I would archive everything (zip/rar/sit/etc.). That would probably get you closest to what you're wanting to achieve.