I found an article on **Cyberfret.com** showing how to play C major scale : 

[The Whole Guitar Neck Mapped Out](http://www.cyberfret.com/guitar-scales/whole-guitar-neck-mapped-out/)

Ref. Pattern 3  

![Pattern chart from aricle](https://i.stack.imgur.com/KHMZH.jpg) 

Well, I can guess how to play the pattern number 3 but, what the purpose of knowing the root note ? I can't understand why in all the articles I've read they refer to it ?