Writing web code (HTML/JS,CSS)

Question

How do you link the codes up on a PC?
Do you need to write the codes separately?
E.g. you write code on a HTML document and then link it up to CSS documents or something?
Help would be appreciated :)

Answer 1

I might have got the wrong interpretation of what you were saying, CSS can be injected into HTML with the HTML tag <style>, and JavaScript can be added with the <script> tag from HTML but to keep everything more organized you can make another file called style.css but if you are to do this the file name must end in whatever language you are using

Example:
script.js