Include Separate JS File

Is there a way to put all of my javascript code that belongs in my html file's head tags into a separate file, and include it in the html head tag? (just like a stylesheet)


-What would I write in the head of my html file?
-How would I start, and end the javascript file?

I googled your question and found:

http://www.webreference.com/programming/javascript/external/