As an example, lets look at the A major scale. As the name suggests, the scale starts on the note 'A', and contains the following 7 notes:
'A' is referred to as the Root note, and we arrive back at A (the octave) after the 7th note (G#), an octave higher. If we refer to our Chromatic Scale (immediately below), we can see the Step Pattern that this scale uses:
The interval between the 1st and 2nd notes of the A major scale (A and B) is two semitones (A to A# = 1 semitone, A# to B = 1 semitone), or one whole tone. On the guitar this would be an interval of two frets, since one fret = one semitone.
If we write out all the intervals like this for all the notes of the A major scale, we find that:
So we have found the Step Pattern for a major scale:
On the guitar, we could play it on the G string (3rd string) like this:
This applies to all major scales. So, if we wanted to work out the scale of C major, for example, referring to the chromatic scale presented earlier, we would end up with:
Exercise: Try working out the major scales for B, D, E, F, G and C#.