The Diatonic Scale is also known as the major scale and has 7 modes. Don't let the discussion of modes freak you out. They are just scales you have already learn with a different root note. More on that later.

The diatonic scale is a 7 note scale, and contains all of the notes of the pentatonic scale. So again it is going to look very familiar.

E|---|-5-|---|-6-|-8-|---|
B|---|-5-|-6-|---|-8-|---|
G|-4-|-5-|---|-7-|---|---|
D|---|-5-|---|-7-|---|---|
A|---|-5-|---|-7-|-8-|---|
E|---|-5-|---|-7-|-8-|---|

You can see the table of notes on a fretboard below. Starting on the fith fret you can impose the scale above. You'll notice that every note on the scale is a major note (no flats or sharps). The notes for this scale are in red below and the root notes are underlined:

1-E---||-F-|---|-G-|---|-A-|---|-B-|-C-|---|-D-|---|-E-|
2-B---||-C-|---|-D-|---|-E-|-F-|---|-G-|---|-A-|---|-B-|
3-G---||---|-A-|---|-B-|-C-|---|-D-|---|-E-|-F-|---|-G-|
4-D---||---|-E-|-F-|---|-G-|---|-A-|---|-B-|-C-|---|-D-|
5-A---||---|-B-|-C-|---|-D-|---|-E-|-F-|---|-G-|---|-A-|

6-E---||-F-|---|-G-|---|-A-|---|-B-|-C-|---|-D-|---|-E-|
Fret -N----1---2---3---4---5---6---7---8---9--10--11--12
Don't let scales and music theory scare you. You don't really need to know the theory to understand what sounds good. I alway try to give the simplest approach. Master the simple things and then you can learn the more complicated later.

A lot of learn guitar sites overload their visitor with too much STUFF that just makes you confused and ready to give up. We will try to keep things as simple as possible.