download java script instructions

Hello,

It it really JavaScript that you are looking for? Or did you mean Java plug-in?
Anyways, understanding one of those will be far from learning something about an operationg system => http://en.wikipedia.org/wiki/Operating_system

JavaScript is a language that you can use when you create an web page (html for instance), to dialog with your web browser. So it's not really related to your operating system. You do not have to download JavaScript, all web browsers understand this language, except if you disable it in the settings options. So you simply write your own web page with JavaScript in it, and when you display this page in your web browser you will see the effects of your script.

For JavaScript, you can find many tutorials on the web. Here is one of them: http://www.w3schools.com/js/default.asp
Best way to write JavaScript code is to install an IDE, like NetBeans for instance, which can help you with the syntax of that language and tell you if you do something wrong. But there is also time to spend learning how to use the IDE :-(

If you did not man JavaScript in your question, then that's another matter, please let us know!
Regards
Enrico

I did several typing mistakes in my post, sorry for them, I cannot make corrections.
I just have to give here a more direct link to the JS tutorial: http://www.w3schools.com/js/js_intro.asp